Colorado Law & Induced Seismicity 1
Colorado Law & Induced Seismicity
Darlene A. Cypser
Earthquakes can be induced by reservoir impoundment, fluid injection, mining, or oil and
gas extraction. These induced quakes create a risk of personal injury or damage to property. The
quakes induced at the Rocky Mountain Arsenal near Denver in the 1960's caused significant
property damage. Currently, low level seismicity is being induced at several sites in Colorado,
including the Rangely Oilfield, Paradox Valley, and Ridgway Reservoir areas. However, no
Colorado statute specifically prohibits or regulates induced seismicity. If individuals are injured
by seismicity induced in Colorado, they could claim compensation under trespass, negligence or
nuisance theories of liability, but Colorado courts are unlikely to apply strict liability to the
activities that can induce earthquakes.
This research was partially funded by a grant from the Rocky Mountain Mineral Law
The author is an attorney practicing in Boulder, Colorado. The author wishes to thank
Scott D. Davis, Selena Billington, Fran Boler, David P. Phillips, Jon Ake, Dan O'Connell, and
Susan Steel-Weir for their assistance and Chris Cypser for editing the manuscript.
Colorado Law & Induced Seismicity 2
Colorado holds a unique position in the history of induced seismology. The first in-depth
studies of induced seismicity were conducted at the Rocky Mountain Arsenal northeast of
Denver and at the Rangely oil field in northwestern Colorado. The Rocky Mountain Arsenal was
not purposefully chosen as the site of an experiment in induced seismicity, but became one by
default in the 1960's when a disposal well drilled by the Army began triggering quakes.
Originally, Rangely was not intended as a research site either. However, tremors were detected
in the vicinity of the oil field soon after injection for secondary recovery began. With
cooperation from Chevron Oil Company, the operator of the Rangely oil field, U.S. Geological
Survey geophysicists conducted injection experiments in the oil field and confirmed the
relationship between fluid injection and seismicity noted at the Arsenal. These two cases still
stand today as the mostly widely accepted cases of induced seismicity. Since the scientific study
of induced seismicity was essentially born here in Colorado, it is appropriate that the study of the
legal implications of induced seismicity begin here as well.
Human-induced seismicity usually occurs at low levels and rarely causes damage.
However, some induced earthquakes, including those at the Rocky Mountain Arsenal, have
caused serious property damage, and even loss of life. This potential for personal injury and
property damage generates questions about liability.
In this paper, I will first briefly review what is currently known about induced seismicity,
including what activities are believed to induce seismicity, examples of where seismicity has
been induced, and what damages resulted. Then I will discuss in greater depth the history of
induced seismicity in Colorado, the current status of Colorado induced seismicity and the
Colorado Law & Induced Seismicity 3
potential for future seismicity in this state. With this as the scientific and factual background, I
will analyze how Colorado law can be applied to induced seismicity.
II. Induced Seismicity
It is not accurate to say that no earthquakes were induced before the 1960's. Scientists
had noted tremors associated with the filling of Lake Mead in Arizona as early as the 1930's.1 A
study in the 1970's concluded that an earthquake in Wappinger Falls, New York in 1952 was
probably induced by the Trap Rock Quarry and that other earlier quakes may have been mistaken
for blasting at the quarry.2
Historic induced seismicity is difficult to diagnose because fewer seismic networks were
operating in the past. Techniques for discriminating natural from triggered seismicity were also
less well developed. In fact, prior to the Rangely experiment some geoscientists were not willing
to admit the possibly of any human activity triggering an earthquake.3 Seismologists now
recognize several different human activities which can stimulate seismicity including fluid
injection and extraction, mining, quarrying, reservoir impoundment, and underground nuclear
A. Injection-Induced Seismicity
Fluid injection for waste disposal or secondary recovery of oil or gas can trigger
earthquakes. Injecting fluids into deep wells increases the pore pressure in the rocks in the
injection zone and areas communicating with the zone. This change in pore pressure can
decrease the effective normal stress across pre-existing faults making them more likely to slip, as
well as decrease the actual strength of the rock surfaces making them less resistant to slippage.
Nicholson and Wesson4 list more than 30 documented cases of possible injection-induced
Colorado Law & Induced Seismicity 4
quakes in the United States and Canada. Davis and Frohlich5 studied 19 such cases in depth and
found strong evidence to support 12 of them. Notable examples are the quakes associated with
waste disposal in El Dorado, Arkansas6 and Ashtabula County, Ohio,7 the tremors associated
with pressure maintenance projects in the Cogdell oil field near Snyder, Texas and other oil
fields near Kermit, Texas,8 and the seismicity induced in the Geysers geothermal field in
northern California.9 There is also strong evidence for microseismicity induced by solution salt
mining near Dale, New York.10
B. Production-Induced Seismicity
Seismicity has also been associated with production of oil, gas and geothermal energy.
Extracting fluids can cause faults which previously had been slipping aseismically to lock up for
periods of time before slipping seismically. Fluid extraction can also lead to compaction and
underground subsidence which can result in seismicity.
Grasso lists 24 oil fields worldwide associated with seismicity of magnitudes greater than
3 (i.e. earthquakes large enough to be felt). While one seismologist has suggested that the
Coalinga (1983), Kettleman North Dome (1985) and Whittier Narrows (1987) earthquakes in
California may have been induced by oil and gas extraction,11 the proposed mechanism for
inducing these quakes is not widely accepted by other seismologists. On the other hand, there is
substantial evidence of seismicity induced by oil and gas extraction in some oil fields in Texas
including the Imogene, Fashing and Falls City fields in south Texas.12
Some seismologists believe the three 7.0 magnitude Gazli, Uzbekistan (1976 & 1980)
earthquakes were also induced by gas extraction. If this is true, these would be not only the most
damaging production-induced quakes known, but the largest magnitude induced quakes of any
Colorado Law & Induced Seismicity 5
C. Reservoir-Induced Seismicity
Some of the most damaging quakes in the world have been induced by the impounding of
reservoirs. Reservoirs increase stress by adding mass on top of the existing rock formations, and
by increasing the pore pressure under and around the reservoir with results similar to those in
fluid injection cases.
Gupta lists 25 cases of reservoir-induced seismicity which produced quakes of magnitude
4 or greater. Seven of those cases were magnitude 5.5 or greater.14 Lake Mead in Arizona began
inducing quakes when it was filled in 1935. The biggest quake near Lake Mead was magnitude 5
and occurred in 1939.15 Some contend the 5.7 magnitude quake near the Oroville dam in
California in 1975 was reservoir induced, though the case is far from clear.16 However, for the
most part the United States has been lucky. Most reservoir-induced earthquakes in this country
have been of low magnitudes and/or located in isolated areas.
Reservoir-induced quakes over 6th magnitude have occurred in Greece, India, and China
and on the Zambia/Zimbabwe border.17 To date the most devastating of these was the December
1967 earthquake near the Koyna Reservoir in India. This 6.3 magnitude earthquake caused
extensive damage to the town of Koyna Nagar and destroyed almost all the buildings in
Denechiwada, Helwak and Nanel villages. Houses collapsed; bridges were destroyed; roads
cracked. The dam itself suffered considerable damage. Over 1500 people were injured and over
200 were killed.18
C. Mining & Quarrying Induced Seismicity
Underground mining increases stress on surrounding rock and supporting columns when
Colorado Law & Induced Seismicity 6
the supporting mass is removed. This can cause failure of the columns, walls, ceiling or floor,
movement along pre-existing faults, or sometimes new faulting. Surface mining and quarrying
remove mass from above, decreasing the stress bearing down on lower layers of rock. These
lower layers of rock may then adjust to the change in stress by springing upward.
Many seismologists who study mining distinguish seismicity resulting from the collapse
of underground cavities, such as occurred at the Solvay trona mine in Wyoming in February
199519, from quakes resulting from movement along a fault or due to uplifting and only refer to
the latter as a “mining-induced earthquake.” However, sometimes tremors from both are
included in the broader category of “mining-related” seismicity.
Seismicity of some form is probably associated with most mining though precise figures
worldwide are hard to come by. Wong lists 32 cases of significant mine seismicity worldwide.20
Redmayne believes that up to 25% of all earthquakes recorded by the British Geological Survey
may be related to coal mining21 and the Geological Survey of South Africa reports that “the bulk
of the seismic events recorded by the regional network” are tremors resulting from deep mining
operations in the gold fields of Transvaal and the Orange Free State.22
Strong correlations have been found between mining activity and seismicity. Seismicity
slows when work stops for a holiday or a miners' strike and eventually stops when all work on
the mine ends. The number of tremors also varies weekly and diurnally according to the rhythm
of the work at the mine.23
The frequency and severity of mining-induced seismicity tends to increase with increases
in the rate of extraction from the mine and depth of the mine.24 Many who study seismicity
related to mining believe that mining-induced seismicity and damaging rockbursts are increasing
Colorado Law & Induced Seismicity 7
in number and severity as the easier to reach minerals are mined out worldwide and new
technology allows for deeper mines and faster extraction.25
Mining companies have an incentive to study mining-induced seismicity since damage
tends concentrate within the mine. Miners can be injured or killed, and access to productive areas
of the mine can be lost. Research can determine what changes in mining practices may be able to
control damaging events. Research has already determined that the geometry of the mine, and the
sequence and rate of extraction, are important factors in mitigating damage.
While mining-induced earthquakes cause the greatest hazard to the mine and the miners,
where mining takes place in populated areas large numbers of tremors may be felt beyond the
mine and perceived as a nuisance.26 The earthquakes with intensities up to V have been
associated with the Trap Rock quarry in Wappinger Falls, New York, though no property
damage has been reported.27 In the 1940's Katherine and J. Freeman Dixon sued the New York
Trap Rock Company which was operating the limestone quarry in Dutchess County.28 The
Dixons claimed that vibrations caused by blasting at the quarry had damaged their house and
injured Katherine's health. The Referee ruled that vibrations from the quarry constituted a
nuisance which entitled the Dixons to damages and the New York Court of Appeals later upheld
this ruling.29 Research by seismologists in the 1970's determined that earthquakes occurring in
Dutchess County in 1974 and 1952 were probably triggered by the Trap Rock Quarry, and that
other smaller quakes might have occurred earlier and been mistaken for dynamite blasts.30 Thus,
some of the “vibrations” that the Dixons complained of in their nuisance suit may have really
been earthquakes induced by the quarry.
E. Seismicity Induced by Nuclear Explosions
Colorado Law & Induced Seismicity 8
Nuclear explosions at the Nevada test site and under Amchitka Island, Alaska have been
followed by large numbers of small earthquakes beginning just after detonation and continuing
for some weeks. Some tremors are located close to the shot chamber and are primarily due to the
collapse of the underground cavity created by the nuclear explosion. Other small earthquakes
have been observed up to 10 km (6 miles) away. These quakes may have been triggered by
changes in stress caused by the opening of the cavity, changes in pore pressure caused by a
pressure wave created by the explosion, or other stress changes generated by the explosion.31
In the late 1960's several large nuclear explosions at the Nevada Test site resulted in
observable displacements on nearby faults and numerous earthquakes. People became concerned
that such an explosion could trigger a large earthquake which would release as much seismic
energy as the explosion itself or even more. This concern peaked prior to the detonation of a high
yield nuclear device under Amchitka Island in Alaska called the “Cannikan” test. This test was
located over a very active seismic zone in the Aleutian Islands. Environmental organizations
attempted to enjoin the Cannikan test because they felt the Environmental Impact Statement did
not adequately consider the possibility of the test inducing devastating quakes and tsunamis. The
U.S. Supreme Court denied the injunction.32 Seismic activity resulting from the Cannikan test
was primarily associated with the cavity collapse and lasted approximately 36 hours. A few
seismic events of tectonic origin which may have been triggered by the explosion occurred on
nearby faults within the next few weeks. None of these quakes were over magnitude 3.33
Fault movements related to nuclear explosions are due to the release of pre-existing
tectonic strain. While the Cannikan test was fired over a subduction zone where intense seismic
activity is generated, there was evidence that the rocks in the upper few kilometers of Amchitka
Colorado Law & Induced Seismicity 9
Island did not carry any substantial tectonic stress and thus had little to release.
However, the Nevada Test Site exists in an entirely different stress environment allowing
for greater fault movements and stress releases. But no earthquake has been triggered that
released as much seismic energy as the explosion itself.34
In addition to nuclear explosions for weapons tests, the United States has detonated
several nuclear devices in Nevada, New Mexico and Colorado as part of the Plowshare program
in the 1960's and 1970's. The purpose of the Plowshare program was to test “peaceful” uses of
nuclear explosions. The program and related seismicity will be discussed in more detail in the
following section on the history of Colorado induced seismicity.
III. History of Induced Seismicity in Colorado
A. Confirmed Cases of Induced Seismicity
1. Injection-Induced Seismicity
a. Rocky Mountain Arsenal
The Rocky Mountain Arsenal covers 27 square miles of prairie due west of the Denver
International Airport. The land was farmland prior to the establishment of the Arsenal. In 1942
the U.S. government condemned the land for military use and removed the farmers and their
families. The Army Chemical Corps swiftly began constructing the Arsenal for the manufacture
of chemical weapons.35 As soon as the facilities were ready, the Arsenal began producing
mustard gas, Lewisite and chlorine gas.36 The Army produced GB nerve gas at the Arsenal from
1953-1957. Napalm bombs and other incendiary devices were also manufactured at the Arsenal
throughout the Korean War.37 The government also produced hydrazine rocket fuel at the
Arsenal during the 1960's.
Colorado Law & Induced Seismicity 10
Beginning in the late 1940's portions of the Arsenal were leased to private industry for
chemical manufacturing. In 1947, Colorado Fuel & Iron Corporation leased a portion of the
Arsenal to manufacture chlorinated benzenes and DDT. Later Julius Hyman & Company took
over that lease and produced pesticides at the Arsenal till the Shell Chemical Company
purchased the company in 1952. Shell continued the manufacture of pesticides on the Arsenal till
From 1942 through 1955 chemical wastes from these manufacturing processes were
pumped to an evaporative basin near the center of the Arsenal called “Basin A”. During the
summer of 1954 farmers northwest of the Arsenal complained of crop damage due to ground
water contamination. Complaints increased after the GB nerve gas plant began production. In
1955, the Army constructed Basin F, a 96 acre asphalt-lined basin with a special waterproof
membrane, to store the chemical wastes from the Arsenal. From 1955 through 1975 all of the
Arsenal's chemical wastes were pumped to Basin F.39
However, construction of Basin F did not stop the contamination of ground water in and
around the Rocky Mountain Arsenal.40 In 1960 the Army began considering constructing a waste
disposal well on the Arsenal. The plan was to construct a well over 2 miles deep which could
inject the chemical wastes from Basin F between layers of rock far below the surface
groundwater. Army officials thought the wastes would be trapped there and be unable to cause
any further contamination. Construction of the well began in June 1961. The well was completed
in early 1962 and the Army began pumping chemical wastes from Basin F into the deep well on
March 8, 1963.41
At 4:10 pm April 24, 1962 a seismograph near Golden, Colorado recorded an earthquake
Colorado Law & Induced Seismicity 11
from a location northeast of Denver. The quake was too small to be felt -- only magnitude 1.5 --
and would not have been noticed if it had been an isolated event. However, this quake was
followed by over 1500 more earthquakes in the same general area between 1962 and 1967. These
varied from quakes too small to be noticed by humans to some causing moderate damage up to
40 miles from the epicenter.42
Studies by graduate students at the Colorado School of Mines located the epicenters of
the earthquakes and discovered that they were all within 5 miles of the Rocky Mountain Arsenal
disposal well.43 Later studies determined that the epicenters of the quakes were even closer to the
Minor damage caused by 3rd & 4th magnitude earthquakes caught the attention of the
public and raised concerns. As the quakes continued, people began to fear that larger quakes
On November 23, 1965 consulting geologist David M. Evans publicized his opinion that
the pumping activities at the Arsenal well were directly related to this seismic activity.44 He
produced charts comparing the frequency of the earthquakes and the monthly volume of fluid
injected at the Arsenal. The number of earthquakes rose as the volume of wastes pumped into the
well rose and fell as the volume fell.
This publicity prompted studies of the earthquakes and their association with the RMA
disposal well by the U.S. Geological Survey and the Army Corps of Engineers. Colorado
Governor John A. Love directed the Colorado School of Mines to study the earthquake series as
well. As part of its investigation the U.S. Geological Survey established a dense seismic network
on the Arsenal grounds. This network operated during January and February 1966. Data from
Colorado Law & Induced Seismicity 12
this network showed that the epicenters of the earthquakes occurred within a narrow elliptical
zone which included the disposal well.45
As evidence mounted of the relationship between the earthquakes and the disposal of
chemical wastes into the Arsenal well, political pressure grew to end the pumping. The Army
ceased injecting fluid into the Arsenal well on February 20, 1966.46
However, the earthquakes did not immediately cease. As the quakes continued, debates
raged over whether an attempt should be made to remove the wastes injected into the well. Some
scientists said that removal of the fluids would stop the quakes; some said it would make them
worse; and others said that it would make no difference.47 The “pumping out” question became a
hot political issue between U.S. Representative Don Brotzman (Republican) and his Democratic
challenger, former Congressman Roy H. McVicker.48
Before the decision was made three earthquakes larger than any of the previous quakes
struck the area. In April, August and November 1967, 3 earthquakes over magnitude 5 and their
aftershocks rocked the Denver area.
At noon on Monday, April 10, 1967, a magnitude 5.0 earthquake shook the Denver
metropolitan area. There were no injuries. Damage reports consisted mostly of broken windows,
cracked plaster and fallen objects. One hundred and eighteen window panes were broken in
buildings on the Rocky Mountain Arsenal and an asphalt parking split in Derby. Ceiling beams
at the Adams County Golf Course cracked. The walls of school buildings in Boulder were
cracked by the shaking. A man in Commerce City reported that the quake broke pipes in his
home and flooded his basement. Fifteen aftershocks were recorded within the first 5 hours after
Colorado Law & Induced Seismicity 13
The August 8, 1967 quake struck at 7:25 a.m., throwing several people out of their beds
and causing much more damage. The worst damage was concentrated in the Northglenn and
Thornton areas to the northwest of the Arsenal. Windows were broken throughout the area and
merchandise was thrown from the shelves. Rank Gornick of Northglenn Liquors estimated that
he had $10,000 to $12,000 worth of merchandise broken. Fifteen grocery stores northeast of
Denver also suffered breakage damage. The manager of Buddy & Lloyd's Supermarket in
Commerce City estimated their loss from broken merchandise and windows at about $2,000.
Twenty-five windows and three concrete pillars cracked at St. Stephens Lutheran Church in
Northglenn. Many homeowners reported cracked walls, ceilings, floors and foundations in
homes in the Northglenn and Western Hills areas. Water heaters shifted causing connections to
leak. A woman in Lakewood saw a crack open in her concrete driveway during the tremor.
Bricks were knocked loose from a chimney in downtown Denver and fell on a car below.50
Damage from this quake was estimated to total $1 million (1967 dollars).51
In September 1967 after a visit to the Rocky Mountain Arsenal, Representative Don
Brotzman asked the commander of the Army Material Command in Washington, DC to study
the possibility of pumping the well. “The Army declined to seek a consensus from the scientific
community on the advisability of lowering the level of the well and in fact steadfastly insisted
there is no conclusive evidence there was any connection between the well and the earthquakes,”
Brotzman told the Denver Post. Concerned, Brotzman approached President Johnson's science
advisor, Dr. Donald F. Hornig who consulted with experts at MIT on the issue.52
On the night of November 26, 1967 another earthquake over magnitude 5 struck
northeast of Denver. Three 3rd & 4th magnitude aftershocks followed this quake within an hour.
Colorado Law & Induced Seismicity 14
The main quake was felt as far as Laramie, Wyoming. Scores of reports were received of minor
wall, ceiling and floor damage. In Wheatridge an exhaust pipe broke loose from a dryer.53
Residents of the Denver area feared that larger quakes would follow if the waste fluids
were not pumped out of the Arsenal well. The Army felt it was in a “damned if we do & damned
if we don't” situation. If they did pump and a larger earthquake occurred the quake would be
blamed on the pumping. If they did not pump and a larger earthquake occurred it would blamed
on their failure to pump out the fluids.54 A decision was finally made to do some test pumping
with extensive seismic monitoring to establish both the feasibility and safety of pumping out the
Pump tests were carried out by the Army Corps of Engineers between September 3, 1968
and October 26, 1968. The U.S. Geological Survey established a seismic network of 21
seismometers at 17 locations. Fourteen locations were on the Arsenal. Three additional locations
were northwest of the Arsenal across the South Platte River. The system was devised to detect
earthquakes in the vicinity of the Arsenal of -1.0 Richter magnitude or larger. The Army agreed
to halt a pump test if informed by the Geological Survey that certain seismic criteria had been
exceeded. After each of two major pumping periods the frequency of small earthquakes
increased. The Army delayed one test scheduled to begin on September 20, 1968 until October
17 because seismic activity from the first test had not settled down and the U.S.Geological
Survey feared the criteria would be exceeded.56
These tests demonstrated that it would be possible to pump an average of 40 gallons per
minute from the Arsenal well. At that rate it would require approximately 8 years to remove all
the waste that had been pumped down the well. Pressure drops during pumping and increases in
Colorado Law & Induced Seismicity 15
seismic activity created complications. The tests also determined that pumping at the rate of 35-
40 gallons per minute would cause the toxic chemical wastes to flash to steam (which could
further contaminate the area around the Arsenal) unless the wastes were kept cold and under
pressure until released back into Basin F. These requirements would greatly increase the expense
of removing the wastes.57 The remainder of the waste fluid was not pumped from the well.
Since 1967 the earthquakes have been declining.58 The total cost of property damage for
the entire earthquake series through 1982 was approximately $8 million (1990 dollars).59
Most seismologists who have studied this earthquake series believe the high-pressure
injection of fluids into a fault or fracture zone triggered the quakes.60 Larger quakes occurring
over a year after the Army had stopped injecting wastes into the well were caused by the
continued migration of fluid pressures along the fault or fracture zone away from the Arsenal
b. Rangely Oil Field
Scientists with the U.S. Geological Survey and the Army Corps of Engineers were forced
to take a conservative approach to the study of the Rocky Mountain Arsenal quakes due to the
proximity to Denver and other cities. However, they began looking for a site where they could
test their theories about the relationship between high pressure fluid injection into deep wells and
earthquakes. In 1967 W. W. Rubey advised U.S. Geological Survey that the Rangely oil field in
northwestern Colorado might meet their needs.62
The Rangely Oil Field in Rio Blanco County, Colorado is one of the most prolific oil
fields in the Rocky Mountain region. The Rangely Oil Field produced over 815 million bbls
(barrels) through the end of 1995, over eight times the cumulative production of the next most
Colorado Law & Induced Seismicity 16
productive field in Colorado. In 1995 alone the Rangely field produced nearly 9 million
barrels.63 The oil reservoir at Rangely is an anticlinal entrapment about 12 miles long and 5
miles wide. A normal fault cuts through the long axis of the reservoir about one third of the
distance from the southeast end of the field.64 The oil field surrounds the town of Rangely.
The California Oil Company (now a division of the Chevron Oil Company) discovered
the Rangely oil reservoir in 1932 but did not develop the field until 1943. After development
began formation fluid pressure decreased rapidly till 1957. In 1957 the field was unitized under
the management of the California Oil Company. Waterflooding was started in December 1957 to
maximize oil recovery. By 1961 the bottomhole pressure at the northwest end of the field had
recovered and slightly exceeded the initial pore pressure of 2500 psi (pounds per square inch).
By 1963, the bottom hole pressure in that part of the field had increased to about 3,000 psi.
Ninety-eight of the 482 wells in the field were converted to water injection by January 1964.
Seventy-five of the injection wells were located on the periphery of the reservoir, 16 in a 5-spot
pattern on the east flank and 7 in the gas cap. As production from peripheral wells became
uneconomical they were converted to injecting water. The number of injection wells thus
increased steadily, reaching 158 by July 1967. By this time bottom hole pressures were as high
as 4200 psi.65
The Uinta Basin Seismological Observatory near Vernal, Utah was the closest
seismographic station to the Rangely oil field from 1962 to 1970. This station began operating in
December 1962. It immediately began recording a large number of small quakes in the vicinity
of Rangely.66 There are no prior instrumental records of seismicity in the area and only one
secondhand, unverified record of a pre-injection earthquake. Therefore, seismologists are unable
Colorado Law & Induced Seismicity 17
to establish any correlation between the initiation of waterflooding and the onset of seismic
In November 1967 the U.S. Geological Survey installed four temporary portable
seismographs around the field in an effort to locate the active earthquake areas. These recorded
for 8 days and revealed a pattern of seismic activity that correlated with the areas in the field
where fluid pressure was high.68 This study also showed that the earthquakes clustered in two
places within the Rangely field. The clusters of epicenters lay in the northwest end of the field
and along the south central margin of the field. In both places the pore pressure due to water
injection exceeded the original field pressure.69
A 14 station network of seismometers was installed at the Rangely oil field in the fall of
1969. Between October 1969 and November 1970 approximately 1000 earthquakes were located
with the data collected. Nearly all the quakes were in the south-central part of the field. These
epicenters corresponded to places in the field where the pore pressure exceeded the original pore
pressure of 2500 psi. These quakes ranged in magnitude from -0.5 to 3.5 and none caused
significant damage. The quake epicenters lay along the southwestern extension of a fault
previously mapped by Chevron, but only along that part of the fault where pore pressures were
greater than about 2900 psi. Earthquakes located originated at depths within or below the
In November 1970 the U.S. Geological Survey began an experiment at the Rangely oil
field. Four injection wells straddling the fault zone were backflowed to reduce the pore pressure
in the hypocentral region. The wells were backflowed and pumped out for about 6 months.
Within a short time after backflowing began earthquakes within 3000 feet of the wells decreased
Colorado Law & Induced Seismicity 18
markedly in frequency and ultimately almost ceased.71 Calculations based on the measured
stresses indicated that a pore pressure of at least 3700 psi was required for shear failure.
Earthquakes occurred near the bottom of wells where pressure was around 4000 psi. Seismicity
ceased after pressure in those areas dropped 500 psi.72 The portion of the field without natural
faults did not produce earthquakes even when the fluid pressures were quite high.73
The largest earthquakes recorded at Rangely occurred on March 20, 1995 (mag. 4.8),
April 21, 1970 (mag. 4.6), July 6, 1966 (mag. 4.5) and each caused minor damage to the town of
Rangely.74 Waterflooding continues and larger quakes could occur in the future.
c. Paradox Valley
The induced earthquake series at the Rocky Mountain Arsenal and the Rangely oil field
are fairly well known in the seismological community, but a lesser known case of injection-
induced seismicity is currently being observed by the U.S. Bureau of Reclamation in
The Paradox Valley in southwestern Colorado is an elongated salt anticline near the
border with Utah. The Dolores River crosses the valley by piercing the valley walls
perpendicular to the long axis of the valley. The Dolores River picks up a large amount of brine
in the valley which later flows into the Colorado River. As part of the Colorado River Basin
Salinity Control Project the U.S. Bureau of Reclamation is extracting brine at shallow depths in
the Paradox Valley and reinjecting the brine at high pressure beneath the salt deposits of the
Since this portion of the Colorado Plateau was characterized by low level seismicity, and
other factors indicated a potential for induced seismicity, the Bureau of Reclamation installed a
Colorado Law & Induced Seismicity 19
seismic network in the Paradox Valley in 1983 to determine the background level of natural
seismicity.76 The Paradox Valley Seismic Network consisted of 14 seismometer stations. The
closest was located 2 km (1.2 miles) from the well and the most distant was 30 km (18 miles)
away. Another station was added within 1 km (.6 miles) in the fall of 1995. In the seven years of
monitoring prior to the start of injection, only one to two earthquakes per year were recorded in
the valley. No seismic events at all were within 5 km (3 miles) of the well during this period.77
Two trial periods of injection occurred in late 1991. Both were accompanied by a small
number of earthquakes located very near the injection well. The earthquakes began within 24-48
hours after injection was initiated and ceased shortly after injection stopped. The hypocenters of
the earthquakes were located near the base of the well.78
There were seven periods of fluid injection at various wellhead pressures and injection
rates in the Paradox Valley between July 1991 and September 1995. Seismicity accompanied six
of the seven periods of injection. More than 600 quakes have been recorded in the vicinity of the
well. Analysis of the data collected from the injection tests suggests that during injection
pressures at the well bottom are sufficient to cause slipping on pre-existing faults, as well as
cause new faulting in some intact rock. The injection-induced seismic events are clearly
associated with pre-existing fractures, including some identified from previous oil exploration in
the area. None of these faults is expressed on the surface. There is a general correlation between
injection rate, wellhead pressure and number of quakes observed. The higher the pressure and
injection rate the more quakes observed and the larger magnitude. The largest magnitude quake
through 1995 was 2.6, which occurred halfway through the seventh injection period. Larger
events are possible.79
Colorado Law & Induced Seismicity 20
2. Reservoir-Induced Seismicity
Only 48 miles (80 km) to the southeast of the Paradox Valley is the Ridgway Reservoir.
The region near Ridgway has been the site of some of the largest instrumentally recorded
earthquakes in Colorado (M 5.5 in 1960 and M 4.6 1994).80 Several historic quakes are believed
to have occurred in the region.81
A temporary five station seismic network was operated in the area for 3 months in 1979
around the site of the proposed Ridgway Reservoir as part of the seismotectonic investigation of
the dam site. This temporary network located 22 microearthquakes within or near the seismic
array varying from -0.3 to 2.7 in magnitude. Thirty-four other tremors were recorded but were
too small to locate the source. All of the quakes detected by this temporary network were thought
to be associated with the Ridgway Fault or the connected branch faults. One branch fault, named
the Cow Creek Fault, passes under the damsite and was discovered during excavation for the
dam foundation. The Cow Creek Fault is an eastward dipping normal fault and the bulk of the
Ridgway Reservoir sits on the down-throw side of the Cow Creek Fault.82
Based on the seismic history of the region and the results of the temporary seismic
network, the seismotectonic study concluded that the Ridgway Fault and the branch faults were
active or potentially active. And even though the proposed Ridgway reservoir was not considered
a prime candidate for reservoir-induced seismicity based on dam height or planned volume, the
proximity of active faults to the dam site raised the possibility. For this reason a six (later seven)
station seismic network was installed in the area prior to constructing the Ridgway Dam. This
network monitored seismicity in the area from 1983-1987 to establish a baseline of naturally
Colorado Law & Induced Seismicity 21
occurring seismicity. This baseline study showed a fairly low level of seismicity with a few
events occurring in the vicinity of the Ridgway fault and associated branch faults. No quakes
larger than magnitude 2.0 were observed during this period.83
Filling for storage began in October 1986. The frequency of quakes increased at that time
and has continued to be higher than during the baseline period.84 Seismicity also increased
during test fillings in January 1986 and late September/early October 1986. Since the filling of
the Ridgway Reservoir, seismicity within 5 km of the reservoir has increased by a factor of
seven. The largest event beneath the reservoir to date was magnitude 2.3. A large number of
small events also appear associated with north-trending branch faults including the Cow Creek
fault. The hypocenters of these earthquakes tend to be 7-9 kilometers deep. In addition to the
large number of earthquakes occurring beneath the reservoir, there is a persistent cluster of
seismicity east of the reservoir beneath the Cimarron Ridge. These events are consistent with the
location of the 1960 magnitude 5.5 earthquake. The largest tremor in this area since 1985 was
magnitude 2.8. The hypocenters of these quakes seem to form a plane 6 -9 km below surface and
dipping eastward. No surface faults have been mapped in that area.85
The rapid increase in microseismicity near the reservoir coinciding with initial filling
suggests that increased stress due to the added mass of the water of the reservoir is an important
factor.86 This additional stress on the down throw side of the Cow Creek fault is probably
causing the seismicity in the vicinity of that fault. Whether increases in pore pressure are also
contributing to seismicity in the branch faults or beneath the Cimarron Ridge has not yet been
determined. But a “clear association has been established between reservoir impoundment and
increased seismicity near the dam site.”87
Colorado Law & Induced Seismicity 22
A 4.6 magnitude earthquake occurred on September 13, 1994 on the western edge of the
Ridgway seismic network and was followed by several hundred aftershocks. The hypocenters of
these quakes tended to be deeper than those associated with the reservoir filling, between 9-12
km (5-7 miles) below the surface. Due to the distance from the reservoir (over 12 miles) this
swarm of quakes is not thought to be reservoir-induced.88
The Ridgway Dam Seismic Network is a prime example of the precautions which are
appropriate at the site of a proposed reservoir where reservoir-induced seismicity is possible. Not
only can the data collected from the network and reservoir be used to further understand the
mechanisms of induced seismicity, but this seismic monitoring would provide some warning of
changes in patterns of seismicity related to changes in the reservoir. Such monitoring might have
prevented disasters resulting from reservoir-induced earthquakes in China and India. In
recognition of the importance of maintaining the network the Dam Safety Office of the Bureau
of Reclamation has argued strenuously for the continued funding of seismic monitoring in the
vicinity of Ridgway Reservoir, including arguing that the cost of monitoring the risk of
seismicity created by the reservoir should be a cost of doing business: “The reservoir is
impacting the environment and the environmental changes have the potential to effect the health
and well-being of the public as well as the risk the dam poses to the public. Monitoring the
magnitude of the impact is a project cost and should be reimbursable. The environmental change
and the need to monitor would not be required if the facility were not in existence.” 89 However,
this proposal was vetoed by the Acting Regional Director of the Upper Colorado Region of the
Bureau of Reclamation because the monitoring was “not necessary to monitor the structural
integrity ... or for the operation and maintenance of the dam and reservoir.” 90
Colorado Law & Induced Seismicity 23
4. Mining-Induced Seismicity
“Mining has been extensively carried on in the Rocky Mountain region
since 1859. Of the seismic events recorded in Colorado, possibly 10% may be
large mine blasts or rockfalls associated with blasting.”91
Seismologists in Colorado often must identify and remove recordings of mine and quarry
blasting from their seismic records in order to study the earthquakes recorded. But mining and
quarrying have such a long history in Colorado that mining-induced seismicity would be
expected to be found in this state in addition to the contamination of the seismic record by
blasting and rockfalls. However, very little study has been done of these types of induced
seismicity within Colorado. One notable exception is the Somerset coal mine in Delta and
Somerset Coal Mine
Coal has been mined near Somerset since 1901.92 Coal bumps, heaving rocks and cave-
ins are serious hazards in the Somerset coal mine. In July 1969 a seismometer was installed at
the Somerset mine to study such mining hazards. In the first month the seismometer recorded
1,000 small tremors in and around the mine.93
In the fall of 1969 a temporary seismic network was installed for about two weeks on the
surface near the Somerset coal mines to further study seismic activity associated with mining
hazards. This seismic network operated from August 30 through September 16 with continuous
recording from September 3rd through 16th. During this time 38 tremors were recorded by the
temporary network and the permanent seismometer at the mine recorded 517 tremors.94
Hypocenters for 13 of the 38 tremors recorded by the net could be located and were found to be
Colorado Law & Induced Seismicity 24
within 1 mile of the active areas of the Somerset mine. Six of these hypocenters formed a line
parallel to several faults east and west of the mine. This line of seismicity was thought to result
from the release and unequal distribution of stress caused by the nearby mining. Most of the
other seismicity originated near areas in the mine where pillars were being removed. Only two
events were over magnitude 2.95
In general, this brief study indicated that seismicity in the Somerset coal mining district is
similar in occurrence pattern, depth of focus, and origin, to seismicity associated with coal
mining in the central Utah coal mining district which has been extensively studied.
Additional studies of seismicity and patterns of coal extraction were done in the Somerset
coal mine in 1973 and 1974. Peaks in seismic activity coincided with periods of unstable roof
conditions, bumps and squeezes. Some of this seismicity seemed to be due to stresses caused by
prior mining practices in a lower bed.96
Seismicity near Somerset is likely to continue as long as extraction from the coal mine
5. Nuclear Explosion Induced Seismicity
The Plowshare Project was proposed to find “peaceful” uses for nuclear explosions.
Twenty-seven nuclear tests were conducted as part of the project between December 1961 to
May 1973. Three tests called Gasbuggy, Rulison, and Rio Blanco were designed to demonstrate
the potential for using nuclear explosions to stimulate natural gas recovery from low
permeability sandstone reservoirs. The experiments were successful in increasing gas recovery
from the reservoirs. However, in some cases the gas was far too radioactive to use, and public
opinion “fallout” resulted in a discontinuation of the project in 1973.97
Colorado Law & Induced Seismicity 25
Two of these experiments (Rio Blanco and Rulison) took place in Colorado and one
(Gasbuggy) was just south of the Colorado border. Each of these explosions caused a
considerable amount of ground motion and was felt over a large area. Microseismicity increased
near the blast site after each test but diminished rapidly within a few days.98
Project Gasbuggy consisted of a single 29-kiloton nuclear explosive detonated at a depth
of 1,292 meters about 88 km east of Farmington, New Mexico. The explosive was detonated on
December 10, 1967.99
The Rulison Project was a cooperative project of the Atomic Energy Commission, the
Department of Interior, and the Austral Oil Company and involved detonating a single 43 kiloton
nuclear explosion in the Rulison gas field in Garfield County on September 10, 1969.100 Some
property damage resulted from the shock of the explosion. Damage claims were filed and
promptly settled.101 A seismic network operating near the Somerset mine approximately 41 miles
from the test site recorded an increase in the maximum number of large tremors per day
immediately after the explosion though there was no increase in the absolute number of
Rio Blanco was the third of these experiments and was co-sponsored by CER Geonuclear
Corporation, Equity Oil Company of Salt Lake City, Utah, Lawrence Livermore National
Laboratory (known as Lawrence Radiation Laboratory at the time), and the State of Colorado.
For Rio Blanco three nuclear explosives were detonated at depths of 1752 m (5782 ft.), 1869 m
(6168 ft.), and 2007 m (6623 ft.) in the Piceane Basin in Rio Blanco County northwestern
Colorado. The three explosions were detonated nearly simultaneously at approximately 10 am on
May 17, 1973. The total yield from the three explosions was approximately 90 kilotons. 103
Colorado Law & Induced Seismicity 26
Seismic Engineering/Geological Survey installed and operated seismographs for three
major seismic studies of Project Rio Blanco: the ground motion study, the structural response
study and the aftershock study. The ground motion program consisted of an array of 35
documentation stations to give comparisons between predicted and actual ground motions. The
purpose was to compare low rise structural damage and to help establish insurance rates for
subsequent Plowshare nuclear events.104 No fault displacements were found after the test.105
One seismic monitoring station began operating 1.5 years before Rio Blanco was
detonated to provide background seismicity information. This station continued in operation till
December 17, 1973 (7 months after detonation). This station recorded only one earthquake (<1.0
mag.) within 40 km (24 miles) of the detonation site in the year and a half before detonation.
Seismicity recorded after detonated was confined to within 500 meters (1650 feet) of the
cavity.106 The seismic events varied in magnitude from -0.3 to 2.4 with the majority less than
1.0. Ten were greater than or equal to 1.5 and the largest (2.4) occurred within 82 minutes of
detonation.107 The vast majority (90+ events) of the seismic events occurred within 12 hours of
the detonation.108 After that period events were relatively few in number. Of the 120 seismic
events recorded only one shock was recorded more than 8 days after detonation and none more
than 4 months after detonation.109 The explosion did not seem to have any long term effect on
the natural seismicity of the area.110 Rockfalls were not observed beyond approximately 20 miles
from the detonation site, and claims for seismic damage from the explosion were fewer and less
significant than anticipated.111
In general, the bulk of the seismicity resulting from these three Plowshare tests seems to
have come from the explosions themselves and the subsequent collapse of the test cavity, rather
Colorado Law & Induced Seismicity 27
than from induced fault movements.
B. Unconfirmed Cases
In addition to the above confirmed cases of induced seismicity in Colorado, there have
been numerous rumors of cases of induced seismicity in Colorado. This list includes both cases
which seem to have been disproved by scientific studies, and cases which have not been
sufficiently studied to either prove or disprove.
1. Mining-Induced Seismicity
During 1979 and 1980 the area near the Henderson mine west of Empire, Colorado, was
the site of a large number of seismic events. There were nearly 100 events per day with
magnitudes up to 2.5. The swarm of quakes subsided after the block-caved mine broke through
the surface.112 No studies of this swarm of quakes have been published.
2. Reservoir-Induced Seismicity
Prior to the filling of the Ridgway Reservoir there were no documented cases of
reservoir-induced seismicity in Colorado. Isolated earthquakes anywhere near an artificial lake
sometimes results in rumors of possible reservoir-induced seismicity. However, with the
exception of Ridgway, the cases of reservoir-induced seismicity which have been studied in
Colorado have not been confirmed.
Among the reservoirs that have been associated with seismic activity are: Harvey Gap
(north of Silt, Colorado), Cabin Creek (south of Georgetown), and Blue Mesa (west of
Gunnison).113 Brief investigations of seismicity have also been carried out at other reservoirs.
a. Cabin Creek Reservoirs
Colorado Law & Induced Seismicity 28
In 1967 David M. Evans reported that Ruth Simon of the Colorado School of Mines
Seismological Observatory had noticed occasional tremors originating near Georgetown,
Colorado. Public Service had recently completed two reservoirs in this area. In April 1967 there
was a sudden increase in the number of tremors. Twelve tremors, ranging in magnitude from 1.0
to 1.5 were recorded that month rather than the usual one or two. This burst of activity seemed to
coincide with the filling of the upper reservoir and Evans suggested this might be a case for
In 1972 David Snow wrote that the area near the Cabin Creek Reservoirs had continued
to be seismically active for the following six years, showing daily peaks of seismic activity
lagging several hours behind the daily reservoir peaks resulting from the operation of the
pumped storage facility.115
However, in 1975 Hadley investigated the possibility of reservoir-induced seismicity at
the Cabin Creek Reservoirs and found no evidence of it. After reviewing the seismic history of
the area, Hadley concluded that most of the recorded seismic activity was blasts related to
construction activities. The pattern of the tremors was related to the daily work patterns. 116
b. Blue Mesa Reservoir
Blue Mesa Reservoir on the Gunnison River is another reservoir listed by Simon as one
where seismic activity had been observed. Simon also lists several historic quakes felt in the
Mount Gunnison/Blue Mesa area prior to the building of the reservoir.117 Warner suggested that
the 3.4 magnitude Cimarron earthquake on August 14, 1983 may have been induced by the Blue
Mesa Reservoir.118 However, studies of this earthquake have not attributed it to the reservoir.119
No microseismicity studies of the Blue Mesa Reservoir have been published.
Colorado Law & Induced Seismicity 29
c. Harvey Gap Reservoir
Ruth Simon listed one quake over magnitude 2 at Harvey Gap Reservoir in
Garfield County, Colorado.120 However, no other evidence exists of any potential for reservoir-
induced seismicity and no detailed study has been made of it.
d. Bear Creek Reservoir
A Corps of Engineers' report written prior to the completion of the Bear Creek Reservoir
states: “The installation at Bear Creek, Colorado, may be of interest, since the reservoir will
inundate a known active fault, as evidenced from epicenter locations determined from small
earthquakes.”121 However, microearthquake monitoring conducted over eight months in 1973 by
the Colorado School of Mines for the Corps of Engineers did not record any definite
earthquakes. Six seismic events recorded might be local quakes.122
e. Strontia Springs Reservoir
A temporary seismic network was operated at the Strontia Springs dam site from August
6 to September 11, 1977. Sixty-seven events were recorded within 45 km (27 miles). All were
thought to be blasts.
From January 1, 1978 through July 12, 1978, MicroGeophysical Corporation operated a
temporary seismic network of 5 seismometers near the Strontia Springs dam site to provide
baseline seismicity information. This study located 32 microquakes (only 4 larger than
magnitude 1.0) within 25 km (15 miles) of the dam site. After the baseline monitoring ended
there were two significant local earthquakes within 30 km (18 miles) of the proposed reservoir
A review of the seismicity study by William Spence of the U.S. Geological Survey was
Colorado Law & Induced Seismicity 30
critical of the short length of the baseline study. According to Spence the level of background
seismicity indicated a high level of sheer stress in the area which could be a sign of a potential
for induced seismicity. He recommended that additional stress and seismicity studies be made.123
Excavation for the dam also revealed signs of faulting and sheering under the dam itself.
This raised the possibility of induced seismicity under the dam. 124
MicroGeophysical Corporation established another seismic network around the Strontia
Springs Reservoir site in early September 1982, just after the dam was completed. Monitoring
continued through March 15, 1983. Filling of the reservoir began October 18, 1982. The first
stage of filling ended October 24 when the reservoir reached 5925 feet in depth. This depth was
held till November 6th when the second stage of filling began. Filling continued till a depth of
5995 feet was reached on November 24th. During this six month period of monitoring 91 seismic
events were recorded within 20 km (12 miles). Sixty-five of those events were believed to be
blasting, leaving 26 natural events. This rate was .2 quakes per day higher than the previous six
months of monitoring but still consisted of less than .5 quakes per day. There seemed little
correlation between filling rates or water level and the seismicity. MicroGeophysical Corporation
concluded that there was no evidence of induced seismicity.125
f. Chatfield Reservoir
A seismic network of 5 monitoring stations was installed near Chatfield Reservoir
southeast of Denver and operated for 8 months in 1973. Thirty events were recorded but all were
believed to be blasts or other surface phenomena. Only 6 events might have been local
3. Seismicity Induced by Underground Gas Storage
Colorado Law & Induced Seismicity 31
Leyden Mine/Gas Storage Facility
In January 1972 the U.S. Geological Survey did a preliminary seismic study of the gas
storage reservoir in the Leyden coal mine near Leyden, Colorado. Public Service uses the old
coal mine to store about 2.1 billion cubic feet of natural gas. The company withdraws gas from
the mine during peak demand periods and injects it into the mine during periods of low demand.
The purpose of the study was to look for small tremors caused by the cyclic loading and
unloading of the pillars of the mine as the gas was withdrawn and injected.
For the study eight seismometers were installed over and around the mine. All eight
seismometers operated for 7 days and at least three of them operated for a total of 14 days.
Two types of seismicity were recorded during this short study. The most abundant type
(type I) was only recorded by the seismometers above or very near the mined area. The
investigators postulated that these tremors might be “resonant vibrations” caused by the gas
moving within the mine.127
The second type, type II, registered on all the seismometers but seemed to be located a
couple of miles to the southeast of the mine. These tremors might be associated with the Golden
fault or mines in that area.
The short time span of the study makes it impossible to correlate the recorded seismicity
with gas injections or withdrawals. A much longer study would be necessary to determine if
there was any relationship between seismicity in or near the mine and the storage of gas in the
IV. Induced Seismicity in Colorado Today and Tomorrow
Today the Rocky Mountain Arsenal fault seems quiet again, but seismicity is still being
Colorado Law & Induced Seismicity 32
actively induced at Rangely, Ridgway and Paradox. New cases of induced seismicity may arise
(or be discovered) and the known sites could produce larger, more damaging quakes.
New reservoirs are being proposed. Oil and gas exploration is increasing in some parts of
the state. New mines are being opened and old ones reopened. While there are currently few
waste disposal wells in Colorado, others might be proposed in the future. All of these activities
have the potential for inducing earthquakes.
Reservoirs are usually large government projects requiring rigorous environmental
assessments and public disclosures. However, private projects like oil wells and waste disposal
wells have more limited licensing and siting requirements and their potential for inducing
seismicity is rarely assessed in advance.
And more people are moving to Colorado. This means not only increasing pressure for
more water, power, and minerals, and the generation of more waste, but also that more people
will be living closer to these activities than before. Where there are more people there is greater
potential for property damage and personal injuries if earthquakes are induced.
It is this potential for future induced seismicity, and the possibility of property damage
and personal injuries which raise the possibility of liability.
V. Liability for Induced Seismicity in Colorado
A. Sovereign Immunity
The victims of the Rocky Mountain Arsenal quakes had very little recourse in 1967. At
that time the Arsenal was operated by the Army and the country was in the midst of the Vietnam
War. I have not found any case that was filed against the Army specifically to collect damages
for the earthquakes nor any record of the Army paying any compensation. A class action suit,
Colorado Law & Induced Seismicity 33
McQueary v. Laird,129 was filed in the U.S. District Court for Colorado on June 4, 1969 seeking
to enjoin the storage of chemical weapons at the Arsenal. The pleadings mentioned the recent
earthquakes as a possible means of escape of the chemicals stored at the Arsenal, but the
damages caused by the earthquakes were not mentioned nor was the source of the quakes.
McQueary v. Laird was dismissed on the grounds of sovereign immunity and lack of
jurisdiction.130 On appeal the Tenth Circuit affirmed the dismissal.131 While the Federal Torts
Claim Act (FTCA) was not at issue in this case because the plaintiffs were seeking a declaratory
judgment and an injunction, not damages, statements in the opinion of the Court of Appeals
make it clear that the court felt these activities were discretionary.132 It is likely that any attempt
to file an action under FTCA for damages caused by the induced earthquakes would have also
been dismissed under the “discretionary function” exception of the FTCA.133
Insurance was not helpful since most people did not carry earthquake insurance.134 The
Property Claims Services database shows no earthquake damage claims having been paid in the
state of Colorado between 1960 and 1969.135
The only recourse of the frightened and injured public was politics. People wrote and
called their Senators and Representatives. Challengers lambasted incumbents for not dealing
with the quakes. Reports by the Army Corp of Engineers and the U.S. Geological Survey ended
up on President Lyndon Johnson's desk. Political pressure stopped the injection but did nothing
to compensate people for property damage. Sovereign immunity shielded the inducers of the
Rocky Mountain Arsenal quakes.
1. Colorado Governmental Immunity Act
Most of the inducing activity in Colorado has been done by federal agencies (e.g. the
Colorado Law & Induced Seismicity 34
Army at the Arsenal and the Bureau of Reclamation at Paradox and Ridgway.) If, however, a
reservoir or a waste disposal well owned and operated by the State of Colorado or one of its
subdivisions, such as the Denver Water Department, were to induce seismicity it would be
necessary to determine if the State of Colorado had waived sovereign immunity for the project
under the Colorado Governmental Immunity Act.136 Under this Act “sovereign immunity is
waived by a public entity in an action for injuries resulting from: (f) The operation and
maintenance of any public water facility, gas facility, sanitation facility, electrical facility, power
facility, or swimming facility by such public entity.”137
A reservoir may easily be considered a “public water facility” and a waste disposal well
could be considered a “sanitation facility” under the Act. If so, this would allow individuals
injured by seismicity induced by the project to bring a negligence claim against the “public
entity.”138 However, the Act does not waive immunity for trespass or strict liability claims. 139
2. Federal Torts Claim Act
For federal projects, the most likely approach to seeking compensation would be to file a
claim under the Federal Torts Claim Act (FTCA). The FTCA waives the sovereign immunity of
the United States government for personal injury or damaged property caused by the negligent
act of government employees acting within the scope of their employment. 140 However, the
FTCA prohibits a claim against the U.S. “based upon the exercise or performance or the failure
to exercise or perform a discretionary function or duty”. 141 Two factors must be examined to
determine if the “discretionary function” exception applies 1) whether the challenged act
involves an element of judgment or choice and 2) whether the discretion involved is of the kind
the exception was designed to shield.142 The exception only applies to acts involving judgment
Colorado Law & Induced Seismicity 35
or choice. If a federal statute, regulation or policy specifically prescribes a course of action, the
action is not discretionary. The exception is not intended to shield every kind of choice but only
government actions and decisions based on considerations of public policy.143
Application of the discretionary function exception requires an examination of the nature
of the challenged conduct.144 Where specific behavior is required of federal employees by
federal statute the discretionary function exception does not apply. However, the FTCA still
requires that the law of the state where the event occurred recognize comparable private liability
before there will be federal government liability.145
For example, the Secretary of the Interior is “authorized to construct, operate or
maintain” the salinity control unit in the Paradox Valley, including the injection wells, by 43
U.S.C. §1592 but that statute provides no specifics as to how the facility is to be constructed or
operated. The details, such as the precise location of wells, the depth of wells, the volumes
injected, and the injection pressures, are left to the discretion of the Secretary. As discussed later,
a claim can be made under Colorado tort law for damage caused by negligently inducing
earthquakes. But if the claim was that the Bureau of Reclamation (a division of the U.S.
Department of Interior) had negligently operated the facility at excessive injection pressures or
negligently located the well, the Bureau could claim that the conduct was a “discretionary
function” and that the Bureau was shielded from any potential liability by sovereign immunity.
Would these siting and operation decisions be “decisions based on considerations of public
policy”? The Bureau is required by 43 U.S.C. §1591 to implement the salinity control policy
adopted at the Conference in the Matter of Pollution of the Interstate Waters of the Colorado
River and Its Tributaries. Geology and hydrology may dictate to some extent the most efficient
Colorado Law & Induced Seismicity 36
manner of implementing that policy, but safety and environmental protection would also have to
be considered in siting and operating the wells. A court could easily find that water policy,
environmental protection and public safety were matters of public policy and that the Bureau was
immune from liability for the results of decisions based on these considerations.
Sovereign immunity may sometimes be extended to contractors on government projects
but does not apply to private projects.
B. Colorado Statutes & Regulations
The industries known to induce seismicity, namely: mining, quarrying, oil & gas
extraction, geothermal energy extraction, reservoir impoundment, and deep well waste disposal,
are regulated by state, local and federal authorities to varying degrees. No Colorado state statutes
or regulations explicitly prohibit inducing seismicity or seek to control it. However, some
statutes and regulations could possibly be used for that purpose.
For example, while the statutes and regulations related to reservoirs are primarily aimed
at avoiding flood damage,146 the regulations do require that the geotechnical report submitted to
the state engineer include information on the geology of the area, and Class I dams and some
Class II dams must submit information on faults and seismicity of the area. 147 While the
requirement is somewhat vague and does not explicitly require trenching or seismic monitoring
during the site investigation, it could be interpreted in that manner. Since there is often a
relationship between the amount of water in a reservoir and the seismicity activity associated
with it, the state engineer's power to determine the amount of water that is “safe to impound in
the reservoir”148 could be used to regulate seismicity by regulating the water level.
While the regulations on geothermal leases in Colorado do not require seismic
Colorado Law & Induced Seismicity 37
monitoring, the regulations do authorize the state engineer to order the installation of “meters,
gauges or other measuring devices” 149 and authorize the state engineer to “require corrections in
a manner or method” of any condition in a geothermal lease threatening “the public health and
safety, and the environment.”150 These regulations could be used to limit the potential for
damaging induced earthquakes.
The Colorado Oil and Gas Commission regulates all aspects of oil and gas exploration
and production including injection for secondary recovery, and disposal of salt water and oil
field wastes.151 The Commission is also empowered to enforce the provisions of the federal
Underground Injection Control Program for Class II injection wells152, which contains some
siting and monitoring requirements which may be applicable to induced seismicity. Operators of
underground disposal activities must seek authorization from the Director.153 The application
must contain anticipated injection pressures, but the Director sets maximum injection pressure in
the authorization.154 The Director's power to set maximum injection pressures could be used to
limit seismicity. C.R.S. §34-60-106(11) also requires the Commission to promulgate rules and
regulations to “protect the health, safety, and welfare of the general public in the drilling,
completion and operation of oil and gas wells and production facilities.” This would authorize
the Commission to create regulations intended to mitigate induced seismicity.
Violations of the rules and regulations of the Oil and Gas Commission constitute
negligence per se if the injured party is within the class of persons intended to benefit from the
regulations.155 State statute establishes a private right to sue for injury resulting from failure to
comply with statutes and regulations related to the oil and gas industry.156
The Colorado Surface Coal Mining Reclamation Act also contains some provisions
Colorado Law & Induced Seismicity 38
which could be used to enforce siting and operating requirements to limit potential induced
seismicity. For example, C.R.S. 34-33-126 allows a person who may be affected, and appropriate
government agencies, to petition the Mined Land Reclamation Board to designate an area as
unsuitable for all or certain types of surface coal mining operations if the board determines such
operations could substantially endanger life and property, and C.R.S. 34-33-121, related to
surface effects of underground coal mining, requires an operator to adopt measures to maximize
mine stability and protect off-site areas from damage which may result from underground coal
Ideally, induced seismicity should be considered in site selection and monitoring of these
industries, and control or mitigation should be required if seismicity occurs. Appropriate
agencies should be empowered to enforce these provisions, and compensation should be
available to those injured.
Currently, however, a person who suffers property damage from induced seismicity in
Colorado must depend primarily on the law of common law torts for compensation and
abatement of future injuries.
C. Colorado Common Law Torts
If quakes similar to the Arsenal quakes were triggered by a private individual or a
corporation in Colorado today, the inducer could be liable under several tort theories. I will
consider the applicability of trespass, negligence, private nuisance and strict liability.
In Colorado, trespass is the physical invasion of property without the owner's permission.
Trespass requires only the intent to do the act constituting, or inevitably causing, the intrusion.
Colorado Law & Induced Seismicity 39
No negligence, or intent to cause harm, is necessary. Colorado does not differentiate between
“direct” and “indirect” injuries in trespass.157 A person who sets in motion a force which, in the
usual course of events, will damage another's property commits trespass when that force enters
that property, and thus that person becomes liable for any resulting damages.158
In Cobai v. Young, the Colorado Court of Appeals applied this rule to an “improvement”
constructed by the landowner which “propagates a damaging force.”159 In this case the
“improvement” was a house with a roof constructed in a way that caused snow to slide off and
strike the side of the neighbor's house in a forceful manner. Each time the snow slid off the
defendant's house it struck the plaintiff's house with a thunderous noise and jarred the house.
This jarring had caused some non-structural damage. The court believed the continuing assault
was likely to cause structural damage in the future. The Court of Appeals agreed with the trial
court's assessment that the defendants controlled “an instrumentality which sets in motion a force
which in the usual course of events [would] damage” the plaintiff's property. The trial court had
ruled this was a continuing trespass, awarded plaintiffs nominal damages of $1 and granted an
injunction. The Court of Appeals affirmed.160
The Court of Appeals also upheld the granting of an injunction in Docheff v. City of
Broomfield, where a new development was discharging water over the plaintiff's land in a
concentrated flow which was causing damage. The court held that the discharge of water is
enjoinable as a continuing trespass if the water is sent down in a manner or quantity greater than
the natural flow.161
In Burt v. Beautiful Savior Lutheran Church, the Court of Appeals upheld the award of
damages for trespass caused by leakage of water onto the plaintiffs' property from a drainpipe
Colorado Law & Induced Seismicity 40
constructed by the defendant.162 The court also rejected the defendant's argument that some of
the defendants should not recover because they had moved to their house after the trespass had
Vibrations or concussions can also be a trespass in Colorado whether applied directly to
the plaintiff's property or as a “force set in motion” which eventually reaches the plaintiff's
property. In Pueblo v. Mace 164 the Colorado Supreme Court held that vibrations of a viaduct
built flush against the plaintiff's building constituted a continuing trespass. In numerous cases in
other jurisdictions concussions caused by blasting were determined to be trespasses.165
Vibrations from heavy equipment have also been deemed trespasses in other jurisdictions.166
Seismicity caused by fault movements triggered by human enterprises is just another type of
vibration set in motion by human intervention and the same rules should apply.
The force released or set in motion by the inducing activity is usually the result of natural
tectonic strain accumulated in the earth. But the precipitation which deposited the snow on
Young's roof and the gravity of the earth which accelerated it off the roof and slammed it into
Cobai's house, are also natural phenomenon. By creating the structure which released or
redirected the natural forces so that they entered another's property, Young committed a trespass.
The same is true of the rainwater and its damaging forces in Burt and Docheff, and the same
would be true of an enterprise inducing the vibrations of an earthquake to travel through the
ground into another's property and cause damage. Thus, a Colorado court could properly
conclude (in an appropriate case) that induced seismicity was a trespass and that the inducer was
liable for any injuries. If the court found a continuing trespass, and a likelihood of future injury,
the court could also enjoin the inducing activity.167
Colorado Law & Induced Seismicity 41
For plaintiffs to recover for damages under a negligence theory in Colorado, they must
show that the defendants breached a duty of care owed to the plaintiffs and that the breach
resulted in the plaintiffs' damages.168 Where damage is foreseeable there is a legal duty to avoid
it.169 A landowner owes a duty of care to prevent injury to people and property outside his land
caused by artificial conditions placed on his land either by himself or a lessee or contractor.170
The existence and scope of that duty is a question of law.171
In Moore v. Standard Paint & Glass Co, the Colorado Supreme Court ruled that a
landowner had “an affirmative duty not to permit its land to remain in an altered state if such
altered state created a condition the natural and foreseeable result of which would result in injury
to the adjoining property.”172
Was it foreseeable that the injection well at the Rocky Mountain Arsenal would cause
earthquakes in the 1960's? No. Very little was known about induced seismicity in the 1950's and
1960's. However, in the 30+ years since the Arsenal quakes began much has been learned about
induced earthquakes, and much more is known about when and where they can be expected.
While it is still not possible to precisely predict when and where they will occur, “foreseeability”
does not require clairvoyance. If you drive through a heavily populated area at high speed, a
crash that injures someone is a foreseeable consequence, even though it may be impossible to
predict where or when it will occur, and you may be lucky enough not to hit anyone.
Now that it is known that certain activities such as injecting fluids into deep wells or
impounding water in reservoirs can cause earthquakes, entities engaged in these activities are
under a duty to investigate the magnitude of the risk involved with their project and ways to
Colorado Law & Induced Seismicity 42
control that risk. Failure to investigate is a form of negligence itself.173 If the information is
obtainable with a reasonable amount of investigation, a court could decide that the inducer
“should have known” of the risk174 and taken steps to mitigate it. “Willful ignorance of a fact is
equivalent to actual knowledge of the fact.”175
In Calvaresi v. National Development Company, Inc.,176 a developer purchased
agricultural land over an abandoned coal mine. At the time of the purchase there was visible
evidence of the mine's existence. The developer removed all signs of mining, had the land
rezoned and a subdivision platted and then sold lots to potential homeowners. Purchasers later
sued the developer when it was determined that the mine posed a substantial subsidence risk and
the county revoked building permits in the subdivision. The jury determined that the developer
knew about the mine and was negligent in failing to investigate the possibility of subsidence and
in failing to disclose the existence of the mine to purchasers.
In Public Service Co. v. Williams,177 a young man was crushed by a landslide caused by
the saturation of a hillside by water leaking from a pipeline. The jury found that the owner of the
pipeline, Public Service Co., had negligently maintained the pipeline and created the landslide
danger of which it “knew or in the exercise of reasonable care and investigation should have
The standard of care required to avoid negligence is that of a “reasonably prudent person
under the circumstances.” Thus, for example, a well operator whose well triggers an earthquake
would be negligent if she “failed to do an act which a reasonably prudent operator would do, or
did an act which a reasonably prudent operator would not do, when faced with a foreseeable risk
of damaging tremors.”
Colorado Law & Induced Seismicity 43
The care required is commensurate with the all circumstances, including the special
knowledge and skill of the parties. A person or organization having special expertise is supposed
to use that expertise to avoid injury.178 People are presumed to have special knowledge and skill
in the field that they make their business,179 and while compliance with industry standards and
government regulations is relevant to establishing due care, it is not conclusive.180 The fact that
industry standards or custom do not require certain precautions is not sufficient to avoid liability
if the organization knows or should know of a risk that a reasonable prudent person would
avoid.181 Negligence can even be found when all applicable laws and regulations are satisfied if
prudence dictates further measures.
Thus a company engaged in an industry that can induce earthquakes, such as reservoir
impoundment, quarrying, and oil and gas extraction, has a legal obligation to be familiar with the
risks inherent in their trade, including induced seismicity. Ignorance of such risks, whether
intentional or simply negligent will not protect them from liability. Such a company is also
obligated to take reasonable steps to mitigate the risk of induced seismicity to avoid injury to
other people or property. Such steps include proper site investigations and seismic monitoring.
Even though Colorado and federal laws and regulations may not currently require that the
potential for induced seismicity be considered in site planning or monitoring, these steps maybe
considered due care by a Colorado court considering an induced seismicity negligence claim.
The greater the risk of injury, the greater the care required by Colorado law.182 Colorado
courts have ruled that certain activities such as the transmission of electricity and propane gas are
inherently dangerous businesses with a high degree of risk requiring “the highest degree of care
which skill and foresight can attain.”183 This higher degree of care is required only when “1) the
Colorado Law & Induced Seismicity 44
activity is inherently dangerous; 2) the defendant possesses expertise in dealing with the activity;
and 3) the general public would not be able to recognize or guard against the danger.”184
Certainly the general public is unable to recognize the danger of induced seismicity or guard
against it. For the most part the general public is unaware there is such a thing as induced
seismicity and even if they were, guarding against the possibility would be difficult and
expensive, and in some cases impossible. Companies entering the inducing business fields
should have the expertise necessary to deal with the risk of induced seismicity because it is one
inherent in their field. To be “inherently dangerous an activity need not be extremely or even
highly dangerous, but must present a foreseeable and significant risk of harm to others if not
carefully carried out.”185 But it must be a situation “where all minds concur that the defendant is
engaged in an activity that possess a high risk of injury to others...”186 The damages which have
occurred in other induced earthquake situations testify to the significance and foreseeability of
the risk of injury. However, whether a court would determine that “all minds concur” that
activities which induce earthquakes are inherently dangerous is questionable.
Regardless of how the courts label the degree of care that earthquake-inducing activities
warrant, the surrounding circumstances must be considered when determining the precautions
required. Those surrounding circumstances include the local population density, the probability
of inducing seismicity, and the potential for damage.
a) Res Ipsa Loquitur
The doctrine of res ipsa loquitur is a rule of evidence creating a rebuttable presumption
that the defendant's negligence caused the injury. Before the rule will be applied the plaintiff
must present evidence that 1) the injury is one which ordinarily does not occur without
Colorado Law & Induced Seismicity 45
negligence; 2) responsible causes other than the defendant's negligence have been sufficiently
eliminated; and 3) the negligence is within the scope of the defendant's duty to the plaintiff.187
Courts usually also require that the mechanism or instrument causing the injury be under the
exclusive control of the defendant.188 In general, the circumstances must indicate that the
defendant has superior knowledge or opportunity to explain the event.189
Could the doctrine of res ipsa loquitur be applied to an induced earthquake situation? The
activities which can trigger earthquakes such as geothermal wells, waste disposal wells, oil and
gas wells and reservoirs and mines, are usually under the exclusive control of the operator and/or
owner. Access to information on injection rates and pressures, and extraction rates are usually
limited to the owners and operators of the project. But to claim that the operators have true
control over the tectonic processes themselves would be going too far.
As discussed previously, landowners and lessees do have a duty to prevent injury to those
outside their land by the activities on their land. Whether other responsible causes can be
eliminated will depend upon the circumstances. But can we say that an induced earthquake is the
kind of event which does not ordinarily occur in the absence of negligence? Certainly
microseismicity can be triggered without any negligence. Is the occurrence of a damaging
induced earthquake sufficient to imply there was negligence? At the current state of the science, I
think the answer must be “no”. Thus we must conclude it would not be appropriate to apply res
ipsa loquitur to induced seismicity at this time.190
b) Professional Liability
Colorado Law & Induced Seismicity 46
“Cases involving ... professional malpractice are species of the phylum
denominated `negligence' cases.”191
A professional, such as a seismologist called upon to do an induced seismicity risk
assessment, has a duty to perform with the care that a reasonable and prudent seismologist with
like education and experience would use under similar circumstances. While no government
regulations or written industry standards dictate minimum requirements for such assessments,
scientific literature provides some basic guidelines.192
But to whom does the seismologist owe this duty of care? A seismologist who undertakes
a seismic hazard study for a company either as an independent contractor or an employee has a
duty to the employer to perform that study with the requisite care and report to her employer. If
the seismologist is restrained from making a thorough investigation by her employer, then that
employer accepts the risk of liability.
For an independent scientist who receives permission to use the company's data and
equipment to do a study but is not affiliated with the company in anyway, the nature of the duty
will depend upon the extent of the undertaking and whether the company may have been induced
to rely on that scientist's assessment and thus have forgone making its own study, or hiring other
Generally, there is no duty to prevent a third person from harming another, absent a
special relation between the actor and the wrongdoer or between the actor and the victim.194
Thus a seismologist who has fulfilled her duty to her employer, client, or any others induced to
rely on her assessment probably has no legal duty to inform the general public.195 The doctrine
Colorado Law & Induced Seismicity 47
of respondeat superior imputes fault to the employer for acts of the employee but not the reverse.
An employee is not vicariously liable for the torts of the employer.196
3. Private Nuisance
A private nuisance is a non-trespassory interference with another's use and enjoyment of
his property. The plaintiff must show that the defendant's interference was unreasonable and
substantial.197 It is not enough that the defendant's actions offended the plaintiff's particular
aesthetic sense.198 The interference must be substantial enough to be offensive, inconvenient, or
annoying to a normal person in the community.199
Both business and residential uses may be enjoined if they constitute a nuisance to an
adjoining property owner or resident, regardless of compliance with zoning ordinances or
regulations. 200 Colorado does not recognize the defense of “coming to a nuisance.” The owner
of land does not have the right to maintain a nuisance merely because he constructed it before
someone else moved there.201
Liability for a private nuisance is based on one of three types of conduct: 1) an intentional
interference; 2) a negligent interference; or 3) conduct so dangerous to life or property, and so
abnormal or out-of-place in its surroundings, as to invoke strict liability.202
Induced earthquakes causing physical damage would certainly substantially interfere with
the use and enjoyment of property.203 Low magnitude induced seismicity which does not cause
any actual physical damage could also constitute a private nuisance in Colorado if it is
sufficiently annoying or inconvenient. Vibrations can cause various physical and psychological
reactions.204 Low level seismicity can be especially annoying if felt at frequent intervals, as
Colorado Law & Induced Seismicity 48
occurs in induced earthquake swarms, and can raise fears of damaging quakes to come.
Courts in other jurisdictions have ruled that vibrations caused by heavy equipment,
quarrying and mining, and other uses of explosives were private nuisances.205
4. Strict Liability
Colorado courts have applied strict liability for “ultra hazardous activities” or
“abnormally dangerous activities” under very limited circumstances. In the past it was applied to
fires caused by locomotives, impoundment of reservoirs, and the use of explosives.
In Union Pacific Railroad v. DeBusk,206 the Colorado Supreme Court stated that the
statute207 which made railroads strictly liable for fire set by their engines was not a change in law
but merely declarative of the common law of England as adopted by the state.208 But in 1916 the
Colorado Supreme Court ruled that the statute “was intended to cover the whole law upon the
subject” and thus superseded the common law.209
Formerly, the builders and owners of dams and reservoirs were held strictly liable for
injuries resulting from flooding. 210 Here, too, the courts stated that the original statute 211 was
based on common law.212 However, the “tort reform” legislation of 1986 changed this. The
current statute provides that owners or operators of reservoirs are only liable for injuries caused
by water escaping from their reservoir due to overflow or failure of the reservoir if the escape
was due to negligence.213
The Colorado Supreme Court has consistently applied strict liability to damages resulting
from blasting.214 However, recovery for damages caused by an explosion of stored dynamite
requires proof of negligence in this state.215
In City of Northglenn v. Chevron, Judge Carrigan of the U.S. District Court for
Colorado Law & Induced Seismicity 49
Colorado216 surmised that Colorado would extend strict liability to the storage of gasoline in
residential areas. His arguments were: 1) that Colorado had denied liability for storage of
dynamite in an earlier case (Liber v. Flor) because it had occurred in a sparsely populated, rural
county with a long mining history, and 2) that in the intervening years there had been substantial
development of strict liability law. He predicted that the Colorado Supreme Court would be
persuaded by Sections 519 and 520 of the Restatement (Second) of Torts and Yukon Equipment,
Inc. v. Fireman's Fund Insurance Co.217
However, Colorado courts have refused to apply strict liability to the transfer of
gasoline,218 the transfer of natural gas219, and the disposal of caustic chemicals.220
Thus, the use of explosives is the only activity which currently triggers common law
strict liability in Colorado. While the citation of Watson v. Mississippi and section 519 of the
Restatement (Second) of Torts with approval in Garden of the Gods Village221 suggests the
possibility of extending strict liability to other activities, the refusal of the court to apply it in
these other situations suggests a general reluctance on the part of the Colorado courts to expand
the use of strict liability. While strict liability can be appropriately applied to induced
earthquakes under the rule of Rylands v. Fletcher and the “ultrahazardous activities” and
“abnormally dangerous activities” standards of the first and second Restatements of Torts222, this
reluctance to expand its use in Colorado leads me to doubt that Colorado courts would apply
strict liability to induced earthquakes.
The Rocky Mountain Arsenal near Denver, Colorado was the site of some the most
damaging induced earthquakes in the United States. Colorado has had other cases of induced
Colorado Law & Induced Seismicity 50
seismicity which caused little or no damage. While the Arsenal quakes have ceased, there are
currently at least three active cases of induced seismicity in Colorado. Additional cases may be
initiated or discovered in the future and currently inducing sites could trigger larger earthquakes.
This potential for stronger quakes combined with Colorado's increasing population, makes
property damage and personal injury from induced earthquakes more likely in the future unless
adequate project assessments are made and precautions taken. The steps taken at Paradox and
Ridgway provide models for the assessment and monitoring of potential induced seismicity
Some Colorado statutes and regulations may be useful in encouraging the avoidance of
damaging induced seismicity, but the primary source for compensation for injuries would be
common law torts. If reasonably prudent precautions are not taken in the siting and operation of
potential inducing activities, then those injured may seek compensation under negligence or
nuisance law in Colorado. Trespass may also be grounds for compensation for damage from
induced earthquakes but strict liability based on the concept of “abnormally dangerous activities”
is unlikely to be applied in Colorado.
Colorado Law & Induced Seismicity 51
Coal bump: A violent failure of rock within a coal mine that does not cause damage to
the mine itself.
Earthquake: A sudden motion or trembling in the earth caused by the abrupt release of
slowly accumulated strain.
Earthquake swarm: A series of minor earthquakes, none of which may be identified as
the main shock.
Epicenter: The point on the earth's surface directly above the focus of an earthquake.
Fault: A fracture or zone in a rock along which there has been displacement of the sides
relative to one another.
Focus of an earthquake: The initial underground rupture point of an earthquake.
Hypocenter: The focus of an earthquake.
Induced earthquake: An earthquake, which, through human intervention, occurs at a
different time, or place, or with a greater magnitude or intensity than a natural quake.
Intensity: A measure of the effects of earthquake at a particular place.
Magnitude: A measure of the strength of an earthquake, as determined by seismographic
Microseismicity: Small earthquakes.
Normal stress: The intensity of stress across a fault.
Pore Pressure: The fluid pressure in the pores of rocks.
Rock burst: A violent failure of rock in a mine that causes damage to the excavation.
Colorado Law & Induced Seismicity 52
Seismic: Pertaining to an earthquake or earth vibration, including those artificially
Tectonic: Related to the natural deformation of the earth's crust.
Triggered earthquakes: Seismic activity stimulated by natural or unnatural causes.
Water Flooding: Injection of water into an oil reservoir to increase production.
Partially Derived from: Dictionary of Geological Terms (Robert L. Bates & Julia A.
Jackson, eds., 3rd ed. 1984, Anchor Press).
Colorado Law & Induced Seismicity 53
1. David W. Simpson, Triggered Earthquakes, 14 Ann. Earth Planetary Science 21 (1986).
2. Paul W. Pomeroy, et al, Earthquakes Triggered by Surface Quarrying -- The Wappinger Falls,
New York Sequence of June, 1974, 66 Bull. Seismological Soc'y Am. 685 (1976).
3. Richard V. Hughes, Denver's Man-Made Earthquakes--Fact or Fancy? Mines Magazine, July
1968, at 22.
4. Craig Nicholson and Robert L. Wesson, Triggered Earthquakes and Deep Well Activities 139
Pure & Applied Geophysics 561 (1992).
5. Scott D. Davis and Cliff Frohlich, Did (or Will) Fluid Injection Cause Earthquakes - Criteria
for a Rational Assessment 64 Seismological Res. Letters 207 (1993).
6. Maximum magnitude 3.0 reached in December 1983; no damage. Craig Nicholson and
Robert L. Wesson, Triggered Earthquakes and Deep Well Activities 139 Pure & Applied
Geophysics 561 (1992).
7. Maximum magnitude 3.6 reached July 1987; no damage reported. Craig Nicholson and Robert
L. Wesson, Triggered Earthquakes and Deep Well Activities, 139 Pure & Applied Geophysics
8. Cogdell field: Maximum magnitude 4.6 reach July 1978; Max. Intensity V; minor damages in
Snyder, Carlsbad, Fluvanna, Justiceburg and Peacock, Texas. Damages consisted of broken
windows, mirrors, and cracked plaster. Scott D. Davis and Wayne Pennington, Induced Seismic
Deformation in the Cogdell Oil Field of West Texas, 79 Bull. Seismological Soc'y Am. 1477
(1989) and Scott D. Davis, et al, A Compendium of Earthquake Activity in Texas (1989).
Near Kermit, Texas: Maximum magnitude 3.4 reached August 14, 1966; Max. Intensity VI;
Damages reported in Kermit included broken windows and dishes, cracked walls and broken jars
in grocery stores. Scott D. Davis, et al, A Compendium of Earthquake Activity in Texas
9. Maximum magnitude 4.0, reached September 1992.
10. Maximum magnitude was .8, reached in November of 1973; The tremor was not felt. Craig
Nicholson and Robert L. Wesson, Triggered Earthquakes and Deep Well Activities 139 Pure &
Applied Geophysics 561 (1992).
11. Arthur McGarr, On A Possible Connection Between Three Major Earthquakes in California
and Oil Production, 81 Bull. Seismological Soc'y Am. 948 (June 1991).
Colorado Law & Induced Seismicity 54
12. The largest felt in Fashing, Texas was magnitude 4.3 on April 9, 1993. This quake caused
major damage to the Warren Petroleum Plant near the epicenter. Several reinforced concrete
foundation blocks cracked or broke. One pipe connection cracked and there were several
stretched bolts and one broke bolt. Damage to surrounding residences was minor. Scott D.
Davis, et al, The April 9, 1993 Earthquake in South-Central Texas: Was it Induced by Oil and
Gas Production? 85 Bull. Seismological Soc'y Am. 1888 (1995)
The Fall City area experienced its largest quake on July 20, 1991. The magnitude was 3.6.
Pleasanton's largest quake was 3.9 and occurred March 3, 1984. Damages were minor, including
cracked plaster and widening of concrete cracks. Scott D. Davis, et al, A Compendium of
Earthquake Activity in Texas (1989).
13. J. R. Grasso, et al, The Three M-7 Gazli Earthquakes, Usbekistan, Central Asia: The
Largest Seismic Energy Releases by Human Activity, Abstracts XXI Gen. Assembly Int'l
Union Geodesy & Geophysics A363 (1995); L. M. Plotnikova, et al, Induced Seismicity in the
Gazly Gas Field Region, 99 Gerlands Beitrage zur Geophysik 389 (1990); David W. Simpson
& William Leith, The 1976 and 1984 Gazli, USSR, Earthquakes--Were They Induced? 75 Bull.
Seismological Soc'y Am., 1465 (1985).
14. Harsh K. Gupta, Reservoir-Induced Earthquakes (1992)
15. Dean S. Carder, Reservoir Loading and Local Earthquakes, Engineering Geology Case
Histories #8 at 51 (1970).
16. See: J. L. Beck, Weight-induced Stresses and the Recent Seismicity at Lake Oroville,
California, 66 Bull. Seismological Soc'y Am. 1121 (1976); M. Lee Bell & Amos Nur, Strength
Changes Due to Reservoir-Induced Pore Pressure and Stresses and Application to Lake Oroville,
83 J. Geophysical Res. 4469 (1978); Charles G. Bufe, et al, Oroville Earthquakes: Normal
Faulting in the Sierra Nevada Foothills, 192 Science 72 (1976).
17. Harsh K. Gupta, The Present Status of Reservoir Induced Seismicity Investigations with
Special Emphasis on Koyna Earthquakes, 118 Tectonophysics 257, 269 (1985).
18. Harsh K. Gupta & B. K. Rastogi, Dams and Earthquakes (1976). Seismicity has
continued in the area with damaging quakes occurring in 1973, 1980 and 1993-94. Seismicity
has also increased since the filling of the Warna Reservoir nearby, raising the possibility of
another devastating quake. B.K. Rastogi, et al, Renewed Seismicity Around Koyna Reservoir in
India During 1993-94, Abstracts XXI Gen. Assembly Int'l Union Geodesy & Geophysics
A367 (1995) and Letter from Harsh K. Gupta to author (August 1995) (on file with author).
Colorado Law & Induced Seismicity 55
19. Magnitude 5.3. Two miners were trapped and one subsequently died. See Peter L. Swanson
& Frances M. Boler, The Magnitude 5.3 Event and Collapse of the Solvay Trona Mine:
Analysis of Pillar/Floor Failure Stability, U.S. Bureau of Mines Open File Rep. #86-95 (1995).
20. Ivan G. Wong, Recent Developments in Rockburst and Mine Seismicity Research, Rock
Mechanics 1103 (Tillerson & Wawesik, eds., 1992).
21. D.W. Redmayne, Mining Induced Seismicity in UK Coalfields Identified on the BGS
National Seismograph Network, Engineering Geology of Underground Movements,
Geological Soc'y Eng. Geology Special Publication No. 5, at 405 (F.G. Bell, et al, eds., 1988).
22. L.M. Fernadez, et al, Catalog of Earthquakes in South Africa and Surrounding Oceans
for 1988, Geological Survey, Dept. of Mineral and Energy Affairs, South Africa (1992).
23. D.W. Redmayne, Mining Induced Seismicity in UK Coalfields Identified on the BGS
National Seismograph Network, Engineering Geology of Underground Movements,
Geological Soc'y Eng. Geology Special Publication No. 5, at 405, 409 (F.G. Bell, et al, eds.,
1988); P. Styles, et al, Microseismic Monitoring for the Prediction of Outbursts at Cynheidre
Colliery, Dyfed, S. Wales, Engineering Geology of Underground Movements, Geological
Soc'y Eng. Geology Special Publication No. 5, at 423, 427 (F.G. Bell, et al, eds., 1988); N.G.W.
Cook, Seismicity Associated with Mining, 10 Engineering Geology 99, 115 (1976).
24. Henry S. Hasegawa, et al, Induced Seismicity in Mines In Canada -- An Overview, 129 Pure
& Applied Geophysics 423, 427 (1989).
25. Ivan G. Wong, Recent Developments in Rockburst and Mine Seismicity Research, Rock
Mechanics 1103, 1103 (1992); Markus Bath, A Rockburst Project at Uppsala, Proc. 2d Conf.
on Acoustic Emission/MicroSeismic Activity in Geologic Structure & Materials, 5 Series on
Rock & Soil Mechanics, 89 (1980).
26. D.W. Redmayne, Mining Induced Seismicity in UK Coalfields Identified on the BGS
National Seismograph Network, Engineering Geology of Underground Movements,
Geological Soc'y Eng. Geology Special Pub. No. 5, 405, 412 (F.G. Bell, et al, eds., 1988).
27. 3.3 mag. Maximum Intensity V; Paul Pomeroy, et al, Earthquakes Triggered by Surface
Quarrying--The Wappinger Falls, New York Sequence of June, 1974 66 Bull. Seismological
Soc'y Am., 685 (1976).
28. Dixon v. New York Trap Rock Corp., 58 N.E.2d 517 (N.Y. 1944).
29. 58 N.E.2d 517 (1944).
30. Paul W. Pomeroy, et al, Earthquakes Triggered by Surface Quarrying--The Wappingers
Colorado Law & Induced Seismicity 56
Falls, New York Sequence of June, 1974, 66 Bull. Seismological Soc'y Am. 685 (June 1976).
These quakes were the result of removal of large volumes of rock from the surface. The
underlying rock then shifted in response to the change in stress.
31. Carl Kisslinger, A Review of Theories of Mechanisms of Induced Seismicity, 10
Engineering Geology 85 (1976).
32. Committee for Nuclear Responsibility, Inc. v. Schlessinger, 404 U.S. 917 (1971).
33. Carl Kisslinger, A Review of Theories of Mechanisms of Induced Seismicity, 10
Engineering Geology 85, 86-87 (1976).
35. RMA Prehistory, Eagle Watch, August 1992 at 4-5.
36. 1940s, Eagle Watch, August 1992 at 7.
37. 1950s, Eagle Watch, August 1992 at 8-9.
38. id. See also, The Rocky Mountain Arsenal, EPA Fact Sheet, December 1991.
39. Land v. U.S., 29 Cl. Ct. 744, 747 (1993).
40. In 1969 a physical inspection of Basin F revealed that not only was the basin leaking but that
a whole section of the protective membrane was gone. Land v. U.S. 29 Cl. Ct. 744, 748 (1993).
41. 1960s, Eagle Watch, August 1992 at 10-11; See also, J. H. Healy, et al, The Denver
Earthquakes, 161 Science 1301 (1968).
42. Maurice W. Major & Ruth B. Simon, A Seismic Study of the
Denver (Derby) Earthquakes, 63 Q. Colo. School Mines 9 (Jan. 1968).
43. Poh-Hsi Pan, The 1962 Earthquakes & Microearthquakes near Derby, Colorado,
(1963) (unpublished Master's Thesis T-978, Colorado School of Mines); Yung-Liag Wang,
Local Hypocenter Determinations in Linear Varying Layers Applied to the Earthquakes in
the Denver area, (1965) (unpublished Ph.D. Thesis T-1027, Colorado School of Mines).
44. Robert M. Kirkham & William P. Rogers, Earthquake Potential in Colorado, Colo.
Geological Survey Bull. #43 (1981) [hereinafter Earthquake Potential] and Dept. Army,
Summary History of Rocky Mountain Arsenal, Vol. II 37 (1967-1980) (unpublished
manuscript, available at the Denver Public Library, Western History Collection, Denver, Colo.).
45. J. H. Healy, et al, Microseismicity Studies at the Site of the Denver Earthquakes,
Geophysical and Geological Investigations Relating to Earthquakes in the Denver Area,
Colorado Law & Induced Seismicity 57
Colorado, U.S. Geological Survey Open File Rep. #832, at 14 (J.H. Healy et al, eds., 1966)
46. J. H. Healy, et al, The Denver Earthquakes, 161 Science 1301, 1301 (1968).
47. See Water Wells Called Indicators of Earthquake Movement, Denver Post, August 10, 1967
at 3; Experts to Review Quakes: Arsenal Well in Focus Again, Denver Post, Nov. 27, 1967 at 3;
Gene Lindberg, Evans Favors Pumping Well, Denver Post, November 29, 1967 at 3; Walter
Sullivan, Quake at Denver Called Possible, New York Times, March 8, 1968 at 53; Authorities
Divided on Pumping, Denver Post, March 10, 1968 at 14; Naomi Nover, Arsenal Well: LBJ to
Face Quake Report, Denver Post, March 15, 1968 at 71; William Sullivan, Denver to Get a
'Shrinkage' Test As Quake-Area Well is Tapped, New York Times, July 4, 1968 at 42; and
Arsenal Planning to Pump Well, Denver Post, July 16, 1968 at 4.
48. McVicker Dismayed at Announced Pumping Test, Denver Post, August 4, 1968 at 3.
49. Marilyn Robinson, Record Earthquake Shakes Denver Area,
Denver Post, April 10, 1967 at 1; Marilyn Robinson, Aftershocks Still Rock Denver Area,
Denver Post, April 11, 1967 at 1; David Brand, Record Quake Shakes Widespread Area, Rocky
Mountain News, April 11, 1967 at 5; Earthquake History of Colorado, Earthquake
Information Bulletin, 24, 26-27 (Nov.-Dec. 1970)
50. Marilyn Robinson, Denver Area Jolted by Worst Earthquake, Denver Post, August 9, 1967
at 1 & 3; Earthquake History of Colorado, Earthquake Information Bulletin, 24, 27 (Nov.-
51. Letter from Fred Sharrocks, Office of Earthquakes and Natural Hazards, Federal Emergency
Management Agency. (August 21, 1991).
52. Experts to Review Quakes: Arsenal Well in Focus Again, Denver Post, Nov. 27, 1967 at 3.
53. Denver Rocked by Sharp, Widely Felt Earthquakes, Rocky Mountain News, November 27,
1967, at 1.
54. Naomi Nover, Arsenal Well: LBJ to Face Quake Report, Denver Post, March 15, 1968, at
55. Arsenal Planning to Pump Well, Denver Post, July 16, 1968 at 4; William Sullivan, Denver
to Get a 'Shrinkage' Test As Quake-Area Well is Tapped, New York Times, July 4, 1968 at 42.
56. D. B. Hoover & J.A. Dietrich, Seismic Activity During the
1968 Test Pumping at the Rocky Mountain Arsenal Disposal Well, U.S. Geological Circular
Colorado Law & Induced Seismicity 58
57. Dept. Army, Summary History of Rocky Mountain Arsenal, Denver, CO, Vol. III 16-17
(1967-1980) (Unpublished manuscript, available at Denver Public Library Western History
Collection, Denver, Co.); D. B. Hoover & J.A. Dietrich, Seismic Activity During the 1968
Test Pumping at the Rocky Mountain Arsenal Disposal Well, U.S. Geological Circ. 613
(1969); Paul A. Hsieh & John D. Bredehoft, A Reservoir Analysis of the Denver Earthquakes: A
Case of Induced Seismicity, 86 J. Geophys. Res. 903, 917 (1981).
58. There were approximately 13 quakes detected near the Arsenal by the Geophysical
Observatory at the Colorado School of Mines in 1968; 15 in 1969; 3 in 1970; 5 in 1971; 2 in
1972; 1 in 1978; 2 in 1981; and 2 in 1982. The maximum intensities reported were V in 1968
through 1971; IV in 1972, & 1978; VI in 1981; and III in 1982. Robert M. Kirkham &
William P. Rogers, Colorado Earthquake
Data and Interpretations 1867 to 1985, Colorado Geological Survey Bull. #46, 13-15 (1985).
59. Darlene A. Cypser & Scott D. Davis, Liability for Induced Earthquakes, 9 J. Envtl. L. &
Litig. 551, 557 n.22 (1994).
60. Healy et al., supra note 46, at 1301 & 1309, P. Hsieh & J. Bredehoft, A Reservoir Analysis
of the Denver Earthquakes: A Case of Induced Seismicity, 86 J. Geophysical Res. 903, 919
(1981). and Earthquake Potential, supra note 44, at 100.
61. Earthquake Potential, supra note 44, at 71 & 100; Healy et al., supra note 46, at 1306-9
and Hsieh & Bredehoft, supra note 60, at 914-919.
62. C. B. Raleigh, et al, An Experiment in Earthquake Control at Rangeley, Colorado, 191
Science 1230, 1230 (1976)
63. Scanlon, A. H., Oil and Gas Fields of Colorado: Statistical Data Through 1981, Colo.
Geological Survey Information Series #18, (1982); Colorado Oil & Gas Information
Management System Annual Production Report for 1995 (1996).
64. R. C. Munson, Relationship of Effect of Waterflooding of the Rangeley Oil Field on
Seismicity, Engineering Geology Case Histories #8, 40 (1970).
65. C. B. Raleigh, et al, An Experiment in Earthquake Control at Rangeley, Colorado, 191
Science 1230 (1976); C.B. Raleigh, Earthquakes and Fluid Injection, Underground Waste
Management and Environmental Implications, 273 (1972); James F. Gibbs, Earthquakes in
the Oil Field at Rangely Colorado, U.S. Geological Survey Open-File Report (1972); R. C.
Munson, Relationship of Effect of Waterflooding of the Rangely Oil Field on Seismicity,
Engineering Geology Case Histories #8, at 39 (1970)
66. C.B. Raleigh, Earthquakes and Fluid Injection, Underground Waste Management and
Environmental Implications, 273, 275 (1972); R. C. Munson, Relationship of Effect of
Waterflooding of the Rangely Oil Field on Seismicity, Engineering Geology Case Histories #8,
Colorado Law & Induced Seismicity 59
at 39, 40 (1970)
67. C. B. Raleigh, et al, An Experiment in Earthquake Control at Rangeley, Colorado, 191
Science 1230, 1231 (1976).
68. C. B. Raleigh, et al, An Experiment in Earthquake Control at Rangeley, Colorado, 191
Science 1230, 1231 (1976); James F. Gibbs, et al, Earthquakes in the Oil Field at Rangely
Colorado, U.S. Geological Survey Open-File Report 10 (1972).
69. C.B. Raleigh, Earthquakes and Fluid Injection, Underground Waste Management and
Environmental Implications, 273, 275 (1972).
70. C.B. Raleigh, Earthquakes and Fluid Injection, Underground
Waste Management and Environmental Implications, 273, 275-276 (1972); C.B. Raleigh, et
al, Faulting and Crustal Stress at Rangeley, Colorado, Flow and Fracture of Rocks,
Geophysical Monograph #16, (Heard, et al, ed., 1972).
71. C. B. Raleigh, et al, An Experiment in Earthquake Control at Rangeley, Colorado, 191
Science 1230, 1234 (1976); C.B. Raleigh, Earthquakes and Fluid Injection, Underground
Waste Management and Environmental Implications, 273, 276 (1972).
72. C.B. Raleigh, et al, Faulting and Crustal Stress at Rangeley, Colorado, Flow and Fracture
of Rocks, Geophysical Monograph #16, 275, 282 (Heard, et al ed. 1972)
73. James F. Gibbs, et al, Earthquakes in the Oil Field at Rangely Colorado, U.S.
Geological Survey Open-File Report 21 (1972).
74. From the earthquake database of the National Geophysical Data Center, Boulder, Colorado.
75. Jon Ake, et al, Microseismicity by Fluid Injection in the Paradox Valley of Southwestern
Colorado, 63 Seismological Research Letters 19 (Jan-Mar 1992).
77. Jon P. Ake, personal communication, Sept. 1995.
78. Jon Ake, et al, Microseismicity by Fluid Injection in the Paradox Valley of Southwestern
Colorado, 63 Seismological Research Letters 19 (Jan-Mar 1992).
79. Jon P. Ake, et al, Induced Microseismicity Associated With Deep-Well Disposal of Brine at
Paradox Valley, Colorado, EOS, Proc. Amer. Geophysical Union, Abstracts 473 (1994) and
Jon P. Ake, personal communication (Sept. 1995).
Colorado Law & Induced Seismicity 60
80. Ute R. Vetter, et al, Seismicity Near Ridgway Dam, Southwestern Colorado, 66
Seismological Res. Letters 48 (1995)
81. November 11, 1913 Maximum MMI V plus two felt aftershocks; August 3, 1955 Max. MMI
VI; October 11, 1960 5.5 mb Max. MMI VI followed the next day by a intensity IV aftershock;
January 13, 1962 4.4 local magnitude Max. MMI IV; February 5, 1962 magnitude 4.7 max. MMI
V; September 4, 1966 4.2 mb; April 4, 1967 4.5 mb; September 13, 1994 magnitude 4.6 max
MMI VI. Richard A. Martin, Ridgway Seismographic Network: Preliminary Results of
Network Operation for the Period June 4, 1985 through April 30, 1987, Seismotectonic
Report No. 87-1, Seismotectonic Section, U.S. Bureau of Reclamation (June 1987); William
Lettis, et al, Draft Report, Seismotectonic Evaluation, Colorado River Storage Project &
Smith Fork Project, West-Central Colorado, U.S. Bureau of Reclamation (October 1995).
82. Richard A. Martin, Ridgway Seismographic Network: Preliminary Results of Network
Operation for the Period June 4, 1985 through April 30, 1987, Seismotectonic Report No.
87-1, Seismotectonic Section, U.S. Bureau of Reclamation 1-2 (June 1987).
83. Ute R. Vetter, et al, Seismicity Near Ridgway Dam, Southwestern Colorado, 66
Seismological Res. Letters 48 (1995); Richard A. Martin, Ridgway Seismographic Network:
Preliminary Results of Network Operation for the Period June 4, 1985 through April 30,
1987, Seismotectonic Report No. 87-1, Seismotectonic Section, U.S. Bureau of Reclamation 2
84. Jon P. Ake, et al, Possible Reservoir-Induced Seismicity (RIS) Associated with Ridgway
Dam and Reservoir, 63 Seismological Res. Letters, 19-20 (1992).
85. Ute R. Vetter, et al, Seismicity Near Ridgway Dam, Southwestern Colorado, 66
Seismological Res. Letters 48 (1995); Richard A. Martin, Ridgway Seismographic Network:
Preliminary Results of Network Operation for the Period June 4, 1985 through April 30,
1987, Seismotectonic Report No. 87-1, Seismotectonic Section, U.S. Bureau of Reclamation 2
86. Jon Ake, et al, Possible Reservoir-Induced Seismicity (RIS) Associated with Ridgway Dam
and Reservoir, 63 Seismol. Res. Letters, 19-20 (1992).
87. Issue Paper from Dam Safety Office: Continued Funding of Micro Seismic Networks at
Jackson Lake Dam and Ridgway Dam, U.S. Bureau of Reclamation 1 (January 31, 1994).
88. Ute R. Vetter, Seismicity Near Ridgway Dam, Southwestern Colorado, 66 Seismol. Res.
Letters 48 (1995) and William Lettis, Draft Report, Seismotectonic Evaluation, Colorado
River Storage Project & Smith Fork Project, West-Central Colorado, U.S. Bureau of
Reclamation (October 1995).
Colorado Law & Induced Seismicity 61
89. Issue Paper from Dam Safety Office: Continued Funding of Micro Seismic Networks at
Jackson Lake Dam and Ridgway Dam, U.S. Bureau of Reclamation 2 (January 31, 1994).
90. Memorandum from Rick L. Gold acting for Charles Calhoun, Upper Colorado Regional
Office, Bureau of Reclamation, U.S. Dept. of Interior, Salt Lake City, Utah (June 2, 1994).
91. Ruth B. Simon, Seismicity, Geologic Atlas of the Rocky Mountain Region, 51 (W.W.
Mallory, et al, eds. 1972).
92. Frank W. Osterwald, et al, Instrumentation Studies of Earth Tremors Related to
Geology and to Mining at the Somerset Coal Mine, Colorado, U.S. Geological Survey
Professional Paper #762 9 (1972)
93. id. at 1.
94. id at 14.
95. id at 18.
96. C. Richard Dunrud, Some Engineering Geologic Factors Controlling Coal Mine
Subsidence in Utah and Colorado, U.S. Geological Survey Professional Paper #969, 27-29
97. John Horgan, Peaceful Nuclear Explosions, 275 Sci. Am. 14, 16 (June 1996). During the
first two Rio Blanco production tests in November 1973 and February 1974 the only radioactive
elements detected were tritium and krypton (as gas or triturated water). However, there was no
communication between the upper and lower chimneys. A well was drilled into the bottom
chimney. During a short flow test from the bottom chimney in December 1974, Tritium,
Krypton 85, Cesium 137 and Strontium 90 were detected. Project Rio Blanco, Colorado
Department of Public Health and Environment, Radiation Control Division
(http://www.state.co.us/ gov_dir/cdphe_dir/rc/en_riobl.htm) (1996).
98. Richard Navarro, Rio Blanco Seismic Effects, U.S. Geologic Survey Open-File Report
(1974); Earthquake Potential supra note 44, at 107.
99. Earthquake Potential supra note 44, at 107.
101. Project Rulison, Colorado Department of Public Health and Environment, Radiation
Control Division (http://www.state.co.us/
Colorado Law & Induced Seismicity 62
102. Frank W. Osterwald, et al, Instrumental Studies of Earth Tremors Related to
Geology and to Mining at the Somerset Coal Mine, Colorado, U.S. Geological Survey Prof.
Paper #762 (1972)
103. Earthquake Potential supra note 44 at 107; Richard Navarro, Kenneth W. King, et al,
Rio Blanco Seismic Effects, U.S. Geol. Survey Open-File Report, 2 (1974)
104. Richard Navarro, et al, Rio Blanco Seismic Effects, U.S. Geol. Survey Open-File
Report, 4-5 (1974).
105. Earthquake Potential, supra note 44 at 108 (1981).
106. Richard Navarro, et al, Rio Blanco Seismic Effects, U.S. Geol. Survey Open-File Report,
107. id at 45.
108. id at 40.
109. id at 37.
110. id at 46.
111. Project Rio Blanco, Colorado Department of Public Health and Environment, Radiation
Control Division (http:// www.state.co.us/gov_dir/cdphe_dir/rc/en_riobl.htm] (1996).
112. Micro Geophysical Corp., Strontia Springs Reservoir Seismicity Report, Final Report,
23-24 (Sept. 1983); David Butler, Seismic Hazard Estimation at the Two Forks Dam
Site Near Denver, Colorado, Geotechnical Investigations in Geophysics, 107 (1990); and
Dames & Moore, Geological and Seismologic Investigations for Rocky Flats Plant for U.S.
Department of Energy: Final Report, Appendix G (1981).
113. Earthquake Potential supra note 44 at 108; Ruth B. Simon, Seismicity of Colorado--
Consistency with Those of the Historical Record, 165 Science 897, 898 (1969); Ruth B. Simon,
Seismicity, Geologic Atlas of the Rocky Mountain Region, 51 (W.W. Mallory et al, eds.
114. David M. Evans, Man-made Earthquake--A Progress Report, Geotimes 19 (July Aug.
115. David T. Snow, Geodynamics of Seismic Reservoirs, Proc. Symp. on Flow through
Fracture Rock (1972).
Colorado Law & Induced Seismicity 63
116. L.M. Hadley, Seismicity of Colorado --Vicinity of Cabin Creek Pumped-Storage
Hydroelectric Plant (1975) (Unpublished Master's Thesis #T-1713, Colorado School of Mines).
117. Ruth B. Simon, Seismicity of Colorado--Consistency with Those of the Historical Record,
165 Science 897 (1969); Ruth B. Simon, Seismicity, Geologic Atlas of the Rocky Mountain
Region, (W.W. Mallory et al, eds. (1972).
118. L.A. Warner, Strain Rates, Stress Distribution and Seismic Potential in Central Colorado,
Contributions to Colorado Seismicity and Tectonics: A 1986 Update, Co. Geol Survey Sp.
Pub. #28, 30 (W. P. Rogers & R. M. Kirkham, ed., 1986).
119. Ivan G. Wong & James R. Humphrey, The 14 August 1983 Cimarron, Colorado
Earthquake and the Cimarron Fault, 23 Mountain Geologist 14 (Jan. 1986).
120. Ruth B. Simon, Seismicity of Colorado--Consistency with Those of the Historical Record,
165 Science 897 (1969); Ruth B. Simon, Seismicity, Geologic Atlas of the Rocky Mountain
Region, (W.W. Mallory et al, eds. (1972).
121. Stanley J. Johnson & Ellis L. Krinitzsky, Reservoirs and Induced Seismicity at Corps
of Engineers Projects, Corps of Engineers Misc. Papers S-77-3, at 8 (1977).
122. See MicroGeophysical Corp., Seismological Investigations of the South Platte River
Canyon: Foothills Treatment Plant 41(Sept. 1977); MicroGeophysical Corp., Strontia
Springs Reservoir Seismicity Report: Sept. 13, 1982-March 15,1983 (1983); and Earthquake
Potential supra note 44 at 119.
123. William Spence, Review of the Denver Water Department Induced Seismicity
Program at Strontia Springs, Colorado, U.S. Geological Survey Open File Report 82-64
124. Nathan R. Hopton & Farrukh M. Mazhar, Geotechnical Aspects of Strontia Springs Arch
Dam, HydroPower: Recent Developments, (ed. A. Zagars, 1985).
125. MicroGeophysical Corp., Strontia Springs Reservoir Seismicity Report, Final Report,
126. MicroGeophysical Corp., Seismological Investigations of the South Platte River
Canyon: Foothills Treatment Plant 41 (Sept. 1977); MicroGeophysical Corp., Strontia
Springs Reservoir Seismicity Report: Sept. 13, 1982-March 15,1983 (1983); Earthquake
Potential supra note 44, at 119.
127. Scientists from MicroGeophysics Corp. criticized this study: "However, the interpretation
Colorado Law & Induced Seismicity 64
of the results of this paper is open to question. The 'type I events' they detect are most consistent
with either cars, airplanes, or other cultural interferences. Similar events are detected by most
seismic networks and are usually disregarded." MicroGeophysics Corp., Seismological
Investigations of the South Platte River Canyon: Foothills Treatment Plant, 41-44 (Sept.
1977). While the Leyden mine study is far from conclusive this criticism ignores the statements
in the paper that the investigators recorded "numerous tremors caused by aircraft and railroad
trains" (The Denver and Rio Grande Western line runs just north of the mine.) and that "the
records from these sources are quite distinct and cannot be confused with the records of the two
types of local seismic tremors." Frank W. Osterwald, et al, Preliminary Investigation of
Seismic Tremors in the General Area of the Leyden Coal Mine Gas-Storage Reservoir,
Colorado, U.S. Geological Survey Open File Report #1760 at 11 (1973) Furthermore, vibrations
from cars are more likely to have been recorded by the seismometers near Colorado Highways
93 and 72. However, these seismometers did not pick up the Type I tremors. The Type I
tremors were only recorded by seismometers over the mine which is a rural area where there are
only a few dirt roads. id. at 14.
128. Frank W. Osterwald, et al, Preliminary Investigation of Seismic Tremors in the
General Area of the Leyden Coal Mine Gas-Storage Reservoir, Colorado, U.S. Geological
Survey Open File Report #1760 (1973) and Earthquake Potential supra note 44 at 118.
129. Complaint, McQueary v. Laird, No. C-1461, (D. Colorado, filed June 4, 1969)
(unpublished, available at the National Archives, Denver Federal Center, Lakewood, Colo.) 449
F.2d 608 (1971). One of the plaintiffs was Byron Johnson, a U.S. Representative from Colorado.
Two of attorneys for the plaintiffs were Democrats Richard Lamm, future governor of Colorado,
and Gary Hart, future U.S. Senator for Colorado. This information, together with the fact that no
attempt was made to respond to the motion to dismiss before the deadline, suggests that the case
may have been filed for political reasons.
130. Order filed September 11, 1970, McQueary v. Laird, No. C-1461, (D. Colorado, cased filed
June 4, 1969) (unpublished; available at the National Archives, Denver Federal Center,
Lakewood, Colo.) 449 F. 608 (1971). In support of the Motion to Dismiss, the Defendants
submitted several affidavits including one by Albert H. Rock, Chief of the Safety Office at
Rocky Mountain Arsenal. In his affidavit, Mr. Rock stated: "as regards earthquake activity
during the period of years 1942-1969 there has been no earth tremors or movements which have
caused any damage at Rocky Mountain Arsenal." This sworn statement is contrary to newspaper
accounts published in 1967. See sources at notes 47-53.
131. McQueary v. Laird, 449 F.2d 608 (10th Cir. 1971) Plaintiffs' attorneys also tried to raise
the National Environmental Protection Act as a basis for jurisdiction during oral arguments on
appeal. The Court of Appeals ruled that the needs of national security prohibited NEPA from
forming a basis for jurisdiction. id. at 612.
Colorado Law & Induced Seismicity 65
132. "These challenges raised by the appellants in this case fall within that narrow band of
matters wholly committed to official discretion...." McQueary v. Laird at 612
133. 28 U.S. Code §2680(a). A two prong analysis determines whether the discretionary
function exception applies. First the act must involve an element of judgment, choice or
discretion. It must not be contrary to a specific statute or regulation. Second, the discretion must
be based on considerations of public policy. Daigle v. Shell Oil Co., 972 F.2d 1528, 1537-1543
(10th Cir. 1992).
134. "A local insurance agent said that no damage reports had been received at this office but he
explained that less than one percent of Boulder homeowners carry earthquake insurance which
requires a separate endorsement on a homeowner's policy." Boulder Daily Camera, Nov. 27,
1967 at 2.
135. Letter from Nancy Ritchy, Western Insurance Information Service, to author, July 18, 1991
(on file with author).
136. Colo. Rev. Stat. §24-10-101 et seq.
137. Colo. Rev. Stat. §24-10-106(f)
138. Another possibility would be a claim under Article 2 Section 15 of the Colorado
Constitution which prohibits taking or damaging property without just compensation. The
Governmental Immunity Act does not apply to inverse condemnation actions. Jorgenson v. City
of Aurora, 767 P.2d 756 (Colo. App. 1988).
139. Colo. Rev. Stat. §24-10-106(4).
140. 28 U.S.C. §1346 (b).
141. 28 U.S.C. §2680 (a).
142. Berkovitz v. U.S., 486 U.S. 531 (1988).
144. Ayala v. U.S., 980 F.2d 1342 (10th Cir. 1992) (Ayala V).
145. Ayala v. U.S., 49 F.3d 607 (10th Cir. 1995) (Ayala VII).
146. Colo. Rev. Stat. §87-37-101 et seq and 2 Colo. Code. Reg. §402-1.
147. 2 Colo. Code Rev. §402-1 5.A. (6)(a).
148. Colo. Rev. Stat. §37-87-107.
Colorado Law & Induced Seismicity 66
149. 2 Colo. Code Rev. §402-10 Rule 5.10.
150. 2 Colo. Code Rev. §402-10 Rule 5.12.
151. Colo. Rev. Stat. §34-60-106.
152. 42 U.S.C. §300f et seq and the regulations at 40 C.F.R. §144.26. The UICP regulations
include information, siting and operating requirements that could be used to limit some activity
that might induce earthquakes. However, the regulations were primarily written to prevent
injected wastes from entering sources of drinking water. A well that meets all the requirements
of the UICP could still induce damaging earthquakes.
153. 2 Colo. Code Reg. §404-1 Rule 325 (1997).
154. 2 Colo. Code Reg. §404-1 Rule 325(a)(7) (1997).
155. Gerrity Oil & Nat. Gas Corp. v. Bob Magnes, 923 P.2d 261 (Colo. App. 1995) cert. granted
156. Colo. Rev. Stat. §34-60-114.
157. Burt v. Beautiful Savior Lutheran Church, 809 P.2d 1064, 1067 (Colo. App. 1990) cert.
den. (May 6, 1991) This case essentially overrules the misreading of Colorado trespass law by
the U.S. Tenth Circuit Court of Appeals in Haas v. Levin, 635 F.2d 1384 (1980). In Haas v.
Levin, the Court of Appeals ruled that dust and dirt blowing from an improperly tilled field was
an "indirect invasion" and thus not a trespass. The federal court made no reference to Colorado
trespass cases, but rather based this decision purely a general tort reference (Harper & James,
The Law of Torts) and its discussion of an old English case.
158. Burt v. Beautiful Savior Lutheran Church, 809 P.2d 1064, (Colo. App. 1990) cert. den.
(May 6, 1991) (discharge of water onto neighbor's property); Cobai v. Young, 679 P.2d 121
(Colo. App. 1984)(snow sliding off roof and hitting neighbor's house); Docheff V. City of
Broomfield, 623 P.2d 69 (Colo. App. 1980) cert. den. (Feb. 2, 1981) (discharge of water onto
neighbor's property); Miller v. Carnation Co., 564 P.2d 127 (Colo. App. 1977) cert. den. (Dec.
24, 1973) (invasion by flies bread in chicken manure).
159. Cobai v. Young, 679 P.2d 121, 123 (Colo. App. 1984).
160. id. The houses were located in Crested Butte, Colorado, which receives 300-500 feet of
snow per year. While the court stated that it rejected the contention that the usual amount of
snow an area receives should affect liability, id. at 122, the likelihood of future injury (which is
crucial to the injunction) is higher in Crested Butte than at a place that only receives a couple of
inches of snow per year.
Colorado Law & Induced Seismicity 67
161. Docheff v. City of Broomfield, 623 P.2d 69 (1981) cert. den. (Feb. 2, 1981). In accord,
Hankins v. Borland, 431 P. 2d 1007 (1967).
162. Burt v. Beautiful Savior Luth. Church, 809 P. 2d 1064 (Colo. App. 1990).
163. The court stated that holding that the plaintiff's "moved to the nuisance" and thus failed to
mitigate damages would allow the defendant's to "condemn" part of the neighboring property by
making it unrentable by their trespass. id. at 1069.
164. 285 P.2d 596 (1955).
165. E.g., Watson v. Mississippi River Power Co., 156 N.W. 188 (Iowa 1916), Exner v.
Sherman Power Const. Co., 54 F.2d 510 (2d Cir. 1931), Enos Coal Mining Co. v. Schuchart, 188
N.E. 2d 406 (Ind. 1963).
166. E.g. McNeill v. Redington, 154 P.2d 428 (Cal. Ct. App. 1945) (vibrations from a drop
forging plant constituted a trespass).
167. Generally, Colorado courts will only grant an injunction if there is an imminent danger of
substantial, irreparable injury and the remedy at law is inadequate. American Investors Life
Insurance Co. v. Green Shield Plan, Inc. 358 P.2d 473 (Colo. 1961). If no quakes have occurred,
proving that there is an imminent danger of substantial injury may be difficult. There must be
more than a mere fear or possibility that injury will occur. Martinez v. Winner, 548 F. Supp. 278.
(D. C. Colo, 1982). Unfortunately, enjoining the inducing activity may not immediately end the
seismicity. For example, the three largest of the Rocky Mountain Arsenal quakes occurred over
a year after the Army stopped injecting fluid into the well. Small quakes continued in the area
till 1982. The pressure wave created underground by the fluid injection could not just be "turned
off" and took years to dissipate.
168. Leake v. Cain, 720 P.2d 152, 155 (Colo. 1986). Accord: Palmer v. A.H. Robins CO., Inc.,
684 P. 2d 187, 209 (Colo. 1984) and Calvaresi v. National Development Co., Inc., 772 P.2d 640,
644 (Colo. App. 1988).
169. Metropolitan Gas Repair Serv., Inc. v. Kulik, 621 P.2d 313, 317 (Colo. 1981). Accord:
Palmer v. A. H. Robins Co. Inc. 684 P.2d 187 (Colo. 1984); Leake v. Cain, 720 P.2d 152, 160,
(Colo. 1986); and Calvaresi v. National Development Co., Inc., 772 P.2d 640, 644 (Colo. App.
1988) cert. den. (April 10, 1989).
170. Aldrich Enterprises, Inc. v. U.S., 938 F. 2d 1134 (10th Cir. 1991). A lessor's liability for
the conditions created by a lessee is limited to activities the lessor knew would be carried on at
the time of the lease, and had reason to know would involve an unreasonable risk or require
special precautions that the tenant would not take. 938 F.2d at 1141. In accord, Moore v.
Standard Paint & Glass., 358 P.2d 33 (Colo. 1960).
Colorado Law & Induced Seismicity 68
171. Metropolitan Gas Repair Serv., Inc. v. Kulik, 621 P.2d 313, 317 (Colo. 1981).
172. Moore v. Standard Paint & Glass., 358 P.2d 33, 36 (Colo. 1960).
173. Calvaresi v. National Development Co., Inc., 772 P.2d 640, 644 (Colo. App. 1988) cert.
den. (April 10, 1989).
174. Public Service Co. v. Williams, 270 P. 659, 660 & 663 (Colo. 1928).
175. Denver, S.P. & P.R. Co. v. Conway, 5 P. 142, 147 (Colo. 1884).
176. Calvaresi v. National Development Co., Inc., 772 P.2d 640, 644 (Colo. App. 1988) cert.
den. (April 10, 1989).
177. Public Service Co. v. Williams, 270 P. 659, 660 & 663 (Colo. 1928).
178. LaVine v. Clear Creek Skiing Corp., 557 F. 2d 730 (10th Cir. 1977).
179. Pearce v. Mountain States Telephone & Telegraph Co., 173 P. 871, 872 (Colo. 1918).
180. See, Yampa Valley Elec. v. Telecky, 862 P.2d 252, 257 (Colo. 1993) and Blueflame Gas,
Inc. v. Van Hoose, 679 P.2d 579, 591 (Colo. 1984).
181. Moore v. Standard Paint & Glass Co., 358 P. 2d 33, 37 (Colo. 1960)
182. Blueflame Gas, Inc. v. Van Hoose, 679 P.2d 579 (Colo. 1984).
183. Electricity: Denver Consolidated Electric Company. V. Simpson, 41 P. 499 (Colo. 1895) ;
Denver Consol. Elec. Co. v. Lawrence, 73 P. 39 (Colo. 1903); Arkansas Valley Ry., Light &
Power Co. v. Ballinger, 178 P. 566 (Colo. 1919); Blankette v. Public Service Co. of Colorado, 10
P.2d 327 (1932); Federal Insurance Co. v. Public Service Co., 570 P.2d 239 (Colo. 1977); Smith
v. Home Light & Power, 734 P.2d 1051 (Colo. 1987); Yampa Valley Elec. Assoc., Inc. v.
Telecky, 862 P.2d 252 (Colo. 1993); Mladjan v. Public Service Co. of Colorado, 797 P.2d 1299
(Colo. App 1990). Propane gas: Blueflame Gas, Inc. v. Van Hoose, 679 P.2d 579 (Colo. 1984);
Grange Mutual Fire Ins. Co. v. Golden Gas Co., 298 P.2d 950 (1956); U.S. Fidelity & Guaranty
Co. v. Salida Gas Service Co. 793 P.2d 602 (Colo. App. 1989). Nitroglycerin: E. I. DuPont De
Nemours & Co. v. Cudd, 176 F.2d 855 (10th Cir. 1949); Amusement Park rides: Hook v.
Lakeside Park Co., 351 P.2d 261 (1960). Other jurisdictions have also applied this standard to
butane gas, gasoline, natural gas and anhydrous ammonia. See Blueflame Gas, 679 P.2d 579,
184. Mannhard v. Clear Creek Skiing Corp., 682 P.2d 64, 66 (Colo. App. 1983) cert. den. (May
Colorado Law & Induced Seismicity 69
185. Western Stock Center, Inc. v. Sevot, Inc., 578 P.2d 1045 (1978).
186. Imperial Dist. Services v. Forrest, 741 P.2d 1251, 1255 (Colo. 1987).
187. Holmes v. Gamble, 655 P.2d 405 (Colo. 1982)
188. Hook v. Lakeside Park Co.,351 P.2d 261, 269 (Colo. 1960), Scott v. Greeley Joslin Store
Co., 243 P. 2d 394, 397 (Colo. 1952), Gylling v. Hinds, 222 P.2d 413, 415 (Colo. 1950) and
Zimmerman v. Franzen, 220 P.2d 344, 352 (1950).
189. Boulder Valley Coal v. Jernberg, 197 P.2d 155, 156 (?)
190. The res ipsa loquitur doctrine has also been rejected in cases where injuries occurred during
the shooting of an oil and gas well. See E.I. Dupont de Nemours & Co. v. Cudd, 176 F. 2d 855,
858 (10th Cir. 1949).
191. Greenwell v. Gill, 660 P.2d 1305, 1307 (Colo. App. 1982).
192. E.g., C.B. Raleigh, Earthquakes and Fluid Injection, Underground Waste Management
and Environmental Implications, 273 (1972); Scott D. Davis & Cliff Frohlich, Did (or Will)
Fluid Injection Cause Earthquakes: Criteria for a Rational Assessment, 64 Seismological Res.
Letters 207 (1993); Harsh K. Gupta, Damsite Investigations, Reservoir-Induced Earthquakes,
193. Jefferson County School District R-1 v. Justus, 725 P.2d 767, 770-772 (Colo. 1986). See
also Lester v. Marshall, 352 P.2d 786, 790-791 (Colo. 1960). Even this possibility of liability
may be limited by Colo. Rev. Stat. Sec. §13-21-116(2)(a) which states, "a person shall not be
deemed to have assumed a duty of care where none otherwise existed when he performs a
service or an act of assistance, without compensation or expectation of compensation, for the
benefit of another person." A similar provision applies to public entities and public employees.
Colo. Rev. Stat. §24-10-106.5.
194. Leake v. Cain 720 P.2d 152,160 (Colo. 1986). Accord: University of Denver v. Whitlock,
744 P.2d 54 (Colo. 1987).
195. Rest. 2d of Torts Sec. 314. There may be a moral duty, however.
196. Jackson Marine Corp. v. Blue Fox, 845 F.2d 1307 (5th Cir. 1988)
197. Allison v. Smith, 695 P. 2d 791, 793-794 (Colo. App. 1984).
198. Allison v. Smith, 695 P. 2d 791, 794 (Colo. App. 1984)
199. Northwest Water Corporation v. Pennetta 479 P.2d 398, 400 (Colo. 1970).
Colorado Law & Induced Seismicity 70
200. City of Englewood v. Kingsley, 497 P.2d 1004, (Colo. 1972); Hobbs v. Smith, 493 P.2d
1352, 1354 (1972).
201. Allison v. Smith, 695 P.2d 791,794 (Colo. App. 1984); Krebs v. Hermann, 6 P.2d 907, 908
202. Lowder v. Tina Marie Home, Inc., 601 P.2d 657, 658 (Colo. App. 1979).
203. Darlene A. Cypser & Scott D. Davis, Liability for Induced Earthquakes, 9 J. Envtl. L. &
Litig. 551, 584 (1994).
204. id at n.177.
205. The source of these vibrations have included rocket engines, ice plants, railroad engines, oil
and gas wells, gas turbines, as well as explosives. See D.A. Cypser & S.D. Davis, 9 J. Envtl. L.
& Litig. 551 (1994) note 166. One case, Dixon v. New York Trap Rock Corp., 58 N.E2d 517
(N.Y. 1944), should be especially noted since the Trap Rock Quarry was later found to be
inducing earthquakes and some of the concussions complained of by the plaintiff could have
been induced earthquakes. id. at 584-585.
206. 12 Colo. 294 (1889).
207. Colorado General Statute §2798, was enacted in 1874 and was similar to the current statute
Colo. Rev. Stat. §40-30-103 (1996).
208. 20 P. 754, 754 (1889). The court further stated that the statute was "but a re-enactment pro
tanto of the ancient common law." id. at 759. Colorado adopted the common law of England by
statute as it existed (with some exceptions) in 1607 A.D.. See Colo. Rev. Stat. §2-4-211 (1996).
209. Rhinehart v. Denver & R.G.R. Co., 158 P. 149, 154-5 (1916).
210. Barr v. Game, Fish and Parks Commission, 497 P. 2d 340 (1972); Ryan Gulch Reservoir
Co. v. Swartz 263 P. 728 (Colo. 1928).
211. Colo. Rev. Stat. §148-5-4 (1964).
212. Sylvester v. Jerome, 34 P. 760, 762 (1893) But see Garnet Ditch & Reservoir Co. v.
Sampson, 110 P. 79 (Colo. 1910) in which the Supreme Court stated that common law was not
controlling on the issue, only the Colorado statute applied, and Kane v. Town of Estes Park, 786
P.2d 412, 415 (Colo. 1990) in which the Colorado Supreme Court said that the statutory
provisions were comprehensive and had preempted the common law.
213. Colo. Rev. Stat. §37-87-104.
Colorado Law & Induced Seismicity 71
214. Cass Company Contractors v. Colton, 279 P.2d 415 (Colo. 1955); Garden of the Gods
Village, Inc, v. Hellman, 294 P.2d 597 (Colo. 1956).
215. Liber v. Flor, 415 P.d 332 (Colo. 1966).
216. 519 F. Supp. 515 (1981).
217. 585 P.2d 1206 (Alaska, 1978).
218. Ward v. Aero-spray, Inc., 458 P.2d 744 (1969).
219. Hartford Fire Ins. Co. v. Public Service Co., 676 P.2d 25 (Colo. App. 1983).
220. Forrest v. Imperial Dist. Services, Inc., 712 P.2d 488 (Colo. App. 1985).
221. 294 P.2d 597, 600 (1967).
222. Darlene A. Cypser & Scott D. Davis, Liability for Induced Earthquakes, 9 J. Envtl. L. &
Litig. 551, 569-575 (1994).