ArticlePDF Available

Influence of Solar Cycles on Earthquakes

Authors:

Abstract and Figures

This research inspects possible influence of solar cycles on earthquakes through of statistical analyses. We also discussed the mechanism that would drive the occurrence of increasing of earthquakes during solar maxima. The study was based on worldwide earthquakes events during approximately four hundred years (1600-2010). The increase of earthquakes events followed the Maxima of Solar cycle, and also depends on the tectonic plate location. From 1600 until 1645 events increased during the Maxima in some of the tectonic plates as Pacific, Arabian and South America. The earthquakes analyzed during two grand solar minima, the Maunder (1645-1720) and the Dalton (1790-1820) showed a decrease in the number of earthquakes and the solar activity. It was observed during these minima a significant number of events at specific geological features. After the last minima (Dalton) the earthquakes pattern increased with solar maxima. The calculations showed that events increasing during solar maxima most in the Pacific, South America or Arabian until 1900. Since there were few records during these three centuries we needed additional analysis on modern data. We took the last four solar cycles events (1950-2010) and made similar calculations. The results agreed with the former calculations. It might be that the mechanism for the Sun-Earth connection relies on the solar wind speed. In both records (1600-1900) and (1950-2010) the results showed a significant increase in earthquakes events in some of the tectonic plates linked to solar maxima. The Solar wind energy striking the Earth's magnetosphere affects the entire environment because the pressure on the region increases and the magnetosphere shrinks sometimes four Earth's radii. This sudden compression causes earthquakes in specific plates. During the times of solar minima the pressure from the solar wind on the earth decreases, then the magnetosphere expands and earthquakes happen in a different pattern according to the geological feature on earth's surface less frequently. Solar driven events include coronal mass ejections (CME) and coronal holes, which are at a maximum during the descending phase of solar activity. The tectonic are important because there is heterogeneity in the crust and the tectonic stress depends on each region. The geo-effectiveness of solar wind from a coronal hole only depends on the position of the hole relative to the Earth and for the CMEs an additional factor is their velocity. The influence of these solar events could be detected from electromagnetic variations on the ground prior the earthquakes. The goal in this research was to show the solar events influenced the earthquakes and seismologic events following some special display and also how the Sun's activity played to make earthquakes increase. This paper discussed details of this mechanism, calculations and associated factors.
Content may be subject to copyright.
Vol.3, No.6, 436-443 (2011) Natural Science
http://dx.doi.org/10.4236/ns.2011.36060
Copyright © 2011 SciRes. OPEN ACCESS
Influences of solar cycles on earthquakes
Marilia Tavares, Anibal Azevedo
1Instituto de Fisica, Universidade Federal Fluminense, Niteroi, Brasil; mariliadtavares@gmail.com
2Departamento de Matemática, UNESP Faculdade de Engenharia, Sao Paulo, Brasil
Received 6 February 2011; revised 10 March 2011; accepted 5 April 2011.
ABSTRACT
This paper inspects possible influence of solar
cycles on earthquakes through of statistical
analyses. We also discussed the mechanism
that would drive the occurrence of increasing of
earthquakes during solar maxima. The study
was based on worldwide earthquakes events
during approximately four hundred years (1600-
2010).The increase of earthquakes events fol-
lowed the Maxima of Solar cycle, and also de-
pends on the tectonic plate location. From 1600
until 1645 events increased during the Maxima
in some of the tectonic plates as Pacific, Ara-
bian and South America. The earthquakes ana-
lyzed during two grand solar minima, the
Maunder (1645-1720) and the Dalton (1790-1820)
showed a decrease in the number of earth-
quakes and the solar activity. It was observed
during these minima a significant number of
events at specific geological features. After the
last minima (Dalton) the earthquakes pattern
increased with solar maxima. The calculations
showed that events increasing during solar
maxima most in the Pacific, South America or
Arabian until 1900. Since there were few records
during these three centuries we needed addi-
tional analysis on modern data. We took the last
four solar cycles events (1950-2010) and made
similar calculations. The results agreed with the
former calculations. It might be that the mecha-
nism for the Sun-Earth connection relies on the
solar wind speed. In both records (1600-1900)
and (1950-2010) the results showed a significant
increase in earthquakes events in some of the
tectonic plates linked to solar maxima. The So-
lar wind energy striking the Earth’s magneto-
sphere affects the entire environment because
the pressure on the region increases and the
magnetosphere shrinks sometimes four Earth’s
radii. This sudden compression causes earth-
quakes in specific plates. During the times of
solar minima the pressure from the solar wind
on the earth decreases, then the magnetosphere
expands and earthquakes happen in a different
pattern according to the geological feature on
earth’s surface less frequently. Solar driven
events include coronal mass ejections (CME)
and coronal holes, which are at a maximum
during the descending phase of solar activity.
The tectonic are important because there is he-
terogeneity in the crust and the tectonic stress
depends on each region. The geo-effectiveness
of solar wind from a coronal hole only depends
on the position of the hole relative to the Earth
and for the CMEs an additional factor is their
velocity. The influence of these solar events
could be detected from electromagnetic varia-
tions on the ground prior the earthquakes. The
goal in this research was to show the solar
events influenced the earthquakes and seis-
mologic events following some special display
and also how the Sun’s activity played to make
earthquakes increase. This paper discussed
details of this mechanism, calculations and as-
sociated factors.
Keywords: Solar Cycles; Earthquakes; Currents;
Geomagnetic
1. INTRODUCTION
Sun-Earth connections, are complex and involve, solar
wind, ionosphere and ground. Ritz [1] and Serrano et al.
[2] have investigated the relationship between the solar
activity and earthquakes. The first aim on this paper is to
show a possible connection between sunspots and earth-
quakes. After studying earthquakes in Italy, Mazzarella
et al. [3] thought that seismi city is related to solar activ-
ity and that geomagnetic anomalies are likely to trigger
earthquakes.
Han Yanben, Zengjian, Jinbing and Lihua [4] studied
the relationship between big earthquakes (Ms 8) and
solar activity that occurred in China and western Mon-
golia. They discovered that the occurrence dates of most
of the big earthquakes in and near faults with west-east
strike are close to the maximum years of sunspot num-
M. Tavares et al. / Natural Science 3 (2011) 436-443
Copyright © 2011 SciRes. OPEN ACCESS
437
bers. According to their paper, the appearance of many
magnetic storms in years of maximum solar activityis
the cause an increased number of earthquakes. Magnetic
storms would result in anomalies of geomagnetic field
and in eddy current in the faults, producing earthquakes
with near west east strike. They supposed that initiation
of an earthquake occurs easily since the eddy currents
heat the rocks in the faults and therefore decrease the
shear resistance and the static friction limit of the rock.
Sobolev et al. [5] and Zolotov et al. [6] were interested
in the same subject. They investigated a supposed rela-
tionship between solar wind, particle radiation and
earthquakes.
Earthquakes have inhomogeneous distribution on the
Earth’s surface. The shallow earthquakes happen in areas
that are transform or divergent tectonic boundaries.
Convergent tectonic boundaries have intermediate, deep
and huge earthquakes. There are several parameters con-
sidered on this study such as tectonics, magnitude, depth,
and the heterogeneity in the Earth’s crust for each plate
considered.
Properties of rocks must be understood in addition to
the of electrical properties of igneous and high—grade
metamorphic rocks which make up the bulk of crust in
the depth range where most earthquakes occur, about 7 -
35 km. Freund and Hermance [7-9], showed different
sources of electrical charges generated by rocks. The
first aim of this research is to find out the possible con-
nections between the sunspot variations and their influ-
ence on the earthquakes. We research, search for the
mechanism that would involve Sun (during the Maxima)
and the intensification of earthquakes. Our theory in-
tends to explain the occurrence of earthquakes during the
solar minima as well.
During the minima of sunspots the earthquake events
are detected more often around specific geological fea-
tures such as slip strike faults or subduction zone.
In 2004 [10,11], a multinational consortium led by the
French government launched a new earthquake detection
satellite called DEMETER (for detection of electro-
magnetic emissions transmitted from earthquake re-
gions). DEMETER’s purpose is to study disturbances in
the ionosphere related to natural geophysical events such
as earthquakes, volcanic eruptions or tsunamis. Infrared
radiation detected by satellites may also prove to be a
warning sign of earthquakes to come. Sensors in
NASA’s Terra Earth Observing System satellite regis-
tered what NASA called a “thermal anomaly” on 21
January 2001in Gujarat, India, just five days before a
7.7-magnitude quake there; the anomaly was gone a few
days after the quake. Earthquake forecasters can also
watch for changes in the ionosphere by monitoring very-
low-frequency (3 to 30 kilohertz) and high-frequency
(3 - 30 megahertz) radio transmissions.
Gousheva et al. [12] also made some analysis with the
ionospheric perturbations related to the seismic activity
using the VLF radio signals collected with the DEME-
TER satellite. They monitored on the days of arrival of
high-speed solar wind. They noted a well-pronounced
maximum in the number of earthquakes seen on the day
of arrival of high-speed solar wind and one day after it.
This paper started the analysis of Sun-Earth events
with records from four centuries ago. After 1600statisti-
cal analysis of the data recorded worldwide was more
reliable, likewise for the sunspots recorded.
This study started before the two minima, Maunder
and Dalton, both occurred after 1600. During these two
periods it was possible to observe the importance that
tectonic plates played in the incidence of events. Our
calculations provided results for the entire period
(1600-1900) what included the maxima and the minima
occurred.
The monitoring of the frequency of sunspots and
earthquakes became accurate worldwide after 1900. This
circumstance allowed us to consider parameters such as
depth, magnitude and, location for earthquakes.
Analyzing in both periods (1600-1900, 1950-2010)
the variations in earthquakes and sunspot maxima or
minima suggested that probably electromagnetic distur-
bances from the outer space affected the ground.
Once an earthquake event starts, there is also a forma-
tion of new electric currents because of friction from the
rocks and material around the epicenter. It would explain
the observations of earthquakes in specific geological
areas such as fault, trench, and at the biggest one in scale
in subduction zones. There is a possibility that earth-
quakes happen in clusters. It means earthquakes in some
areas happen in a chain therefore we can predict them.
One must study the electromagnetic Earth’s circuit in
a system that will include ground, atmosphere, iono-
sphere, and Solar Wind interactions simultaneously. The
detection of ionospheric electromagnetic disturbances
prior to earthquakes is of paramount importance for a
future prediction and better understanding of Earth
events.
2. CALCULATIONS
Our initial calculations focused in the long period
from 950 A.D. until 1600 A.D. However, there was a
lack of information for both types of events (sunspots
and earthquakes) until 1600; it was not possible to make
any conclusions with the few data recorded. Therefore,
we choose to restart at 1600 AD for two reasons: solar
cycle and earthquake data files improved after 1600. All
the data in this study came from the National Geophysi-
cal Data Center (NGDC) there are earthquakes recorded
M. Tavares et al. / Natural Science 3 (2011) 436-443
Copyright © 2011 SciRes. OPEN ACCESS
438
since 2150 B.C. To work with the ancient data (before
1600) were impossible. We abandoned the data before
1600 AD.
Nevertheless, on average the earthquake number
available in the period 1600-1900 supplied enough data
for our first analysis and some results. During this period
1600-1900 there was two grand solar minima. One was
the Maunder minimum (also known as the prolonged
sunspot minimum), the name used for the period roughly
spanning 1645-1720, when sunspots became exceed-
ingly rare, as noted by solar observers of the time. Dur-
ing one 30-year period within the Maunder Minimum,
astronomers observed only 50 sunspots. It was not a lack
of observations, because some astronomers carried out a
systematic program of solar observations. The Dalton
minimum was a period of low solar activity lasting from
about 1790 to 1820.The Dalton minimum coincided with
a period of lower than average global temperatures. The
data recorded in the period 1600-1900 were enough to
preliminary information about the behavior of earth-
quakes and solar cycle evolution.
The earthquake events showed a decrease during the
two minima Maunder and Dalton. During both minima
the earthquakes took place in tectonic plates with special
geological features. It is alike solar cycles influenced
earthquakes variations. Next we show two tables con-
structed within the Maunder and Dalton minima, these
tables identified some events that happened in several
special geological features.
Tabl e 1 shows the main characteristics of the plate
boundaries and tectonics in earthquakes during the
Maunder Minima. Divergent plates had small and shal-
low earthquakes; transform boundaries had large, shal-
low earthquakes; convergent boundaries evolve huge,
intermediate earthquakes, even in subduction zones,
which have the greatest depth earthquakes. Trenches are
subduction zones, such as the Marianna, Japan and Peru-
Chile. The Anatolian plates (Turkey) are a left lateral
transform fault. The Iranian system is important because
there is continent- continent collision and strong intra-
plate earthquakes. Most of those faults lies on shear or
transform boundaries. The largest amounts of late Ce-
nozoic shear are localized in faults in Sistan province, in
the far east of the country. This may mean that the pre-
sent-day rates of slip are highest in Sistan. An uneven
distribution of right-lateral shear across eastern Iran may
explain the initiation of the E-W Dasht-e-Bayaz fault
and the bending along the Doruneh fault to the north - as
more clockwise rotation of these E-W faults be expected
in the Far East. In China earthquakes happened in the
strike slip faults such as Sichuan. Earthquakes events
happened in the Pacific area and Arabian plates. Events
that happened in other plates were not enough and they
did not count on this paper [13,14].
Tabl e 2 contains earthquake events, which ensued
during the Dalton minima. These events showed simi-
larities with the Maunder minimum events. Earthquakes
occurred around special land structures such as strike
slip faults and (or) trenches. For this period with low
solar activity we have compared the estimated value of
the sunspots to the number of earthquakes in this period.
The variations of solar activity and earthquakes both
decreased, which demonstrates that on the time-scales of
the order of three centuries, seismic activity followed the
solar activity. The outcomes obtained for the Maunder
minima corroborated the results for the Dalton mini-
mum.
The characteristics of the earthquakes during the Dal-
ton minimum (Ta b l e 2 ) revealed changes in South Pa-
cific, North Pacific, Arabian and South America plates-
decreased in activity.
Apparently during the Maunder minimum not enough
data were available from North America. However, the
earthquake events in other areas happened more around
specific geological features (strike slip faults, convergent
boundaries). The Dalton minima the events happened
more in strike slip faults around transform boundaries
and trenches for convergent boundaries.
In Eurasia most of the activity was around Italy and
Greece, with 88% of earthquakes in this area during the
Table 1 . Characteristics of earthquake events during Maunder (1645-1720) minimum.
Event occurred during the Maunder Minimum
Location (plate) Event occurred vs
Total in each plate (%) Geological feature
South Pacific Phillipines-11/21- ~51% Manilla trench
Indonesia -10/21~47% Sumatran fault-parallel trench with parallel strike slip structure*
South East Pacific Peru-Ecuador-Chile-27/35-~77% Peru-Chile convergent trench
Japan -28/58-~48% Marianna, Japan trench
North Pacific China -24/58`~41% Strike-slip faults in china (Sichuan)
Iran -20/35-~58% Twelfve faults-sinistral, Dextral strike-slip*
Arabian Turkey -14/35-~40% Anatolia fault*
Note*: most faults are strike slip.
M. Tavares et al. / Natural Science 3 (2011) 436-443
Copyright © 2011 SciRes. OPEN ACCESS
439
Table 2 . Characteristics of earthquake events during Dalton (1790-1820) minimum.
Event occurred during the Dalton Minimum
Location (plate) Event occurred vs
Total in each plate (%) Geological feature
Phillipines-3/12- ~25% Luzon trench
South Pacific Indonesia -8/12~67% Sumatran fault system*
Japan -12/28-~42% Marianna, Japan trench
North Pacific China -13/28`~46% Longmenshan fault*
Arabian Iran -10/11-~90% 14 fault*
Eurasia Italy -10/11-~50% S’ Angelo
Greece -10/26-~38% Atalanti, Aquae Lulia*
Chile, Peru -10/18-~56% South America fault*
South America Venezuela, Colombia-8/18-44% Strike slip, subduction zones
North America Missouri, Arkansas, California -8/19-42% New Madrid*, Saint Andreas fault Oaxaca fault*
*faults most Strike slip, transform boundaries or subduction zones.
period. Eurasia is a convergent boundary on the border
in Italy and Greece. In the Mediterranean area there is
even a little subduction zone responsible for deeper
earthquakes. Nevertheless, the earthquakes during the
Dalton minima were around the strike slip faults on
those countries. In the North American plate, the activity
was around the Pacific area, Mexico had some intraplate
earthquake in the Oaxaca fault (strike-slip).The activity
in California was in the San Andreas Fault. The earth-
quakes in Missouri and Arkansas were due to the New
Madrid fault, also a strike slip fault. We showed in those
tables the most important areas where the earthquakes
took place during these two periods. The two Tables
showed places and geological structures where most
earthquake events most happened in both minima. The
tables also show the percentage of the total number of
events and the number of earthquakes focalized in each
area during the period.
Figure 1 shows earthquake data (separated by plates)
in the crust during three hundred years.This figure
analyzed the data in five tectonic plates between 1600-
1900.The earthquake events have been influenced by
different processes depending on Earth’s crust. During
solar maxima the events increased most in Pacific,
Arabian and South America observed since 1600. The
same behaviour took place after the last minima consi-
dered and after the Daltonwas an increase in the earth-
quakes events in Pacific and South America plates. The
results showed that solar activity affected earthquakes in
different processes which depended on Earth’s crust.
During the grand minimas, earthquake activity
decreased and events were reported mostly in specific
plates and geological features, for example North and
South Pacific , South American (subduction zones) and
fewer events in Arabianplates (strike slip fault). The plot
shows how the events behaved during three centuries
1600-1900. This time interval included the two deepest
solar minima, the Maunder and Dalton minima as you
see at the Figure 1. There was a clear variation for each
plate considered, during the Maunder and Dalton min-
ima. In some plates the earthquakes almost disappeared.
Between these two minima earthquakes increased in
Eurasia (before Dalton) and in Pacific and Arabian (after
Dalton).The Maunder minimum coincided with the mid-
dle, and coldest part, of Little Ice Age during which the
world was subjected to bitterly cold winters. Qualita-
tively the number of earthquakes (in some of the tectonic
plates) increased and decreased following the same tra-
jectory of the solar cycles (maxima and minima). Quan-
titatively we would need more events detected to com-
pare both.
In order to find out the accuracy of these results, we
took as a sample a modern period (1950-2010) when the
earthquakes and sunspots have a huge amount of data
recorded. Despite of a possible lack of data during the
first period the modern data will validate or not the re-
sults obtained.
Finally, this study calculated statistically the distribu-
tion of earthquakes and solar cycles for the last part of
20th century and part of the 21st century. Figure 2 shows
the earthquake events during the last part of the last
century and part of 21st century. During each of the 5
solar maxima (1958, 1968, 1979, 1991, 2000) there was
a clear maximum of earthquake events for some tectonic
plates. During the last solar maximum (2000), earth-
quake activity increased on the Arabian, Eurasia and
North Pacific plates. Other plates (Caribbean, Africa and
South America) had fewer events. After 2005, in most of
plates, earthquake events decreased, even with better
data acquisition. This coincides with the decreased solar
activity. The increase of earthquakes depended on the
place they occurred, it depends most of heterogeneity in
the crust and also the geological variables such as if the
tectonic plate is transform, convergent, divergent even if
M. Tavares et al. / Natural Science 3 (2011) 436-443
Copyright © 2011 SciRes. OPEN ACCESS
440
Figure 1. Earthquakes shallowdepth in the period 1600-1900. Note the years of the two
minima, Maunder and Dalton, marked by M’s and D’s.
Figure 2. The last part of the 20th century (1950-2009): earthquakes events in Hemi-
spheres, South and North.
there was in a subduction region. The depth of an earth-
quake is an important parameter and it seems to influ-
ence the correlation between plates and events. The
highest correlation (Sun-Earth) is observed for shallow
earthquake events. In the period (1900-2010) there has
been generally higher solar activity with many sunspots
and CME’s.The instrumentation to detect earthquakes
became more sophisticated during this time. However,
some earthquakes may have been cause by underground
nuclear explosions. It was necessary to limit our data set
to some earthquake parameters, magnitude >4.0, inten-
sity >3.0, and by depth 7 - 35 km. In this paper we limit
the events in the crust, where 85% of earthquakes hap-
pen. The North and South Pacific, contain 70% of earth-
quakes observed worldwide, mainly around the subduc-
tion zones. Those locations are known by huge and in-
termediate events, and also the deepest, earthquakes.
Part of South America earthquakes is on the Pacific side
where there is a convergent boundary with subduction
zones. Eurasia which is part a convergent plate and part
transform or divergent, had decreased earthquake activ-
ity in recent years. Some plates did not change earth-
quake activity during most of the century, with very few
events recorded. Antarctica had just three events in the
20th century. The Caribbean plate had gaps of low activ-
ity or none. The South American remained steady.
M. Tavares et al. / Natural Science 3 (2011) 436-443
Copyright © 2011 SciRes. OPEN ACCESS
441
Comparing the events by Hemisphere, Southern is less
activity during the solar maxima than the Northern. An
anomaly behavior was the activity in Indo-Australian
plates where the number of earthquakes is growing even
after the last solar maxima observed. After 2005 most
plates analyzed even showed a decrease in the earth-
quake events. This paper uses data from only eight of the
plates since the other four plates have not had events
recorded continuously or even frequently.
Figure 3 shows the trend-line for earthquake events
during the last 60 years. The activity increased in the
period of sunspot maxima. It is calculated that a regres-
sion that would show a relationship among tectonic
plates. Probably some plates have an interconnection
with one another concerning earthquakes. They are
North Pacific depth 10 - 20 km, 20 - 30 km, Indo Aus-
tralian 10 - 20 km, Arabian 0 - 10km, Eurasia 10 - 20 km.
If plates appear to have correlated earthquake events,
then an earthquake in one of them induces one in another.
The trend line concerns the North Pacific plate and its
relationship with other plates. If an event happens in the
North Pacific plates the possibility is 31% there will be a
next event in other plates.
The connections among events are very complicated
to analyze; some event may possibly attached to another
one without sun correlation. If one event happens in on
plate it correlates other event in the nearby plate. This
point will be clear up with mathematical models that
give us the probability that one event happen in one or
another plate. It is also possible that some Sun storm
events disturb the ground and ignites a first earthquake
followed by a cluster.
At this point more studies are necessary since the
seismological community attention focused on me-
chanical processes as rocks deform as a macroscopic
body, on when and where micro cracks appear, what role
the water plays and intergranular water films when and
how seismic slip may occur. Seismologists need new
tools that can provide information before the rocks reach
the critical point of rupture. It is necessary to study pre-
earthquake events and seismological electromagnetic
waves before and after an earthquake.
3. RESULTS
We found that during solar minima earthquakes oc-
curred mostly along the strike slip faults that had had a
long rest, such as the New Madrid (1811-1812), Loma
Prieta (1989), Haiti (2010), [15,16]. Some major earth-
quakes happened during solar minima such as observed
by Akhoondzadeh et al. [17]. Besides the seismological
characteristics (they occurred in subduction zones or
strike slip faults), it looked connected with the variations
in the speed of solar wind. Let make a briefly analysis in
the New Madrid earthquakes. It happened 1811-1812 in
a chain of earthquakes. It happened in a minimum be-
tween the Cycle 5 and Cycle 6 those had a very few
number of sunspots during the maxima. They were the
two lowest maxima since 1700. We supposed that Solar
wind pressure has been feeble during this time and the
Earth surface released energy in places where the tec-
tonic was compatible with the observations during other
minima.
Finally, for the last half past of the 20th century (1960-
Figure 3. Earthquake events vs.yearscorrelation and regression line.
M. Tavares et al. / Natural Science 3 (2011) 436-443
Copyright © 2011 SciRes. OPEN ACCESS
442
2001) solar events increase agreed with higher occur-
rence of earthquakes in some of tectonic platesanalyzed.
A rough prediction would give us that earthquakes
should happen regularly in China around the Sichuan
fault system. In Iran or Turkey (around the Anatolian
fault), in South America (Peru-Chile trench), in Eurasia
particularly in the fault system in Italy (those earth-
quakes in Eurasia happened after more than ten years in
a sunspot minimum) in the North America trough of
New Madrid. During the sunspot maxima the earthquake
activity increased in different tectonic plates. However
in some tectonic plates events remained steady or did not
happen at all. This means that the increase of sunspots or
disturbances from CME events operate differently prob-
ably due to heterogeneity of Earth’s crust. Overall, in the
last 60 years the number of earthquakes increased in two
plates, North and South Pacific. During the last solar
maximum the number of earthquakes increased in sev-
eral locations such as Arabian, Eurasia and North and
South Pacific. These last five years or more (after the
maxima), events decreased in all tectonic plates com-
pared to the Sunspot maxima (in 2000).
Correlation and the regression factor calculations
during the last cycles (1960-2010) pointed to the possi-
bility the events are in association with each other. It
could happen in a chain or in a cluster of earthquakes in
the same area or different ones. A better mathematical
model is necessary. Particularly, events that happened in
the North Pacific are likely to happen in the South Pa-
cific as well. These results indicated a connection be-
tween events that make complicate the analysis of
earthquakes versus solar cycles. The effect that the tec-
tonic each plate plays on the earthquakes is of para-
mount importance.
4. SUMMARY AND DISCUSSIONS
There was a clear decrease in earthquakes for the two
grand solar minima examined and an increase in the
number of earthquakes for the last half of the 20th cen-
tury. This increase in solar events, called the Modern
Maxima, coincided with the intensification of earth-
quake events in several plates. More data is needed re-
garding the variations of disturbances in the ionosphere
caused by these variations (solar storms) in the solar
cycles and the variation concerning the dynamic pres-
sure. Dynamic pressure (Dp) affects the flux transfer
from the dayside to night side, and the depending of the
tectonic ground is important. Dynamic pressure is a
function of speed and density of the solar wind. Satel-
lites detect electromagnetic disturbances in the iono-
sphere and in regions such as the South Atlantic anomaly.
It is possible that these disturbances affect the ground
under that region. The main sources of high-speed solar
wind are solar coronal holes and coronal mass ejections
(CME’s). Satellite and ground-based instruments regu-
larly monitor them both and could make it able to fore-
cast periods of enhanced seismic risk. To be geoeffective,
the solar wind from a coronal hole or from a CME has to
first arrive at the Earth, so the geoeffectiveness of solar
wind from a coronal hole or from a CME depends on its
position relative to the Earth. For the CMEs an addi-
tional factor is their size and speed. Faster and wider
CMEs are more geoeffective [18,19].
Solar wind speed which causes more dynamic pres-
sure on Earth’s magnetosphere is the physical mecha-
nism which increases the number of earthquakes. Varia-
tionsin solar wind during a Coronal Mass Ejection event
can exert pressure, deforming and shrinking the magne-
tosphere by 4Re (Earth radius). The tension on magnetic
field lines is analogous to the tension on a violin string.
The pressure will affect the Earth surface in different
ways depending of the tectonic of each region; some
areas are more susceptible to release energy in a form of
earthquake or other analogous phenomena (such as vol-
canoes).
Nowadays, we know that earthquakes and volcanism
occur primarily in those zones where one plate is rub-
bing against the “fault lines”. Earth directed Coronal
Mass Ejections (CME) were very frequent during 2000-
2002. There was a continuous impact of huge amount of
energy, changing the Kp indices (planetary indices) and
free electrons in the upper part of the atmosphere. These
changes in Sun-Earth environment induced by the Sun
have changed the geosphere and atmosphere from time
to time.
A similar explanation for earthquakes happening dur-
ing the minima relies in the Solar Wind decreasing speed.
If the solar speed is lower the magnetosphere relax and
expands again, the consequences are that earthquakes
follow different trajectory this time. Earthquakes will
happen more in geological feature such as strike slip
fault or trenches (subduction zones). Finally, earthquakes
do not follow cycles as solar cycles because it depends
from the Earth’s structure and in fact, it happens in a
sequence determined by the plate and the geological
feature of each of them. It is difficult to find out a direct
connection Solar Maxima and ground since earthquakes
perhaps happening in clusters or related to each other. It
makes events less cyclic and interconnected depending
of the Earth structure of each region under surveillance.
REFERENCES
[1] Ritz, M. (1984) Short communication: A high conductiv-
ity anomaly on the West African craton (MALI). Journal
of Geophysics, 55, 182-184.
[2] Serrano, I., Zhao, D., Morales, J. and Torcal, F. (2003)
M. Tavares et al. / Natural Science 3 (2011) 436-443
Copyright © 2011 SciRes. OPEN ACCESS
443
Seismic tomography from local crustal earthquakes be-
neath eastern Rif Mountains of Morocco, Tectonic Phys-
ics, 367, 187-201.
[3] Mazzarella, A. and Palumbo, A. (1988) Solar geomag-
netic and seismic activity, NuovoCimento C, Serie, 1,
353-364.
[4] Han, Y.B., Guo, Z.J., Wu, Jinbing and Ma, L.H. (2004)
Possible triggering of solar activity to big earthquakes
(Ms 8) in faults with near west-east strike in China.
Science in China Series G Physics, Mechanics and As-
tronomy, 47, 173-181.
[5] Sobolev, G.A., Shestopalov, I.P. and Kharin, E.P. (1998)
Geoeffective solar flashes and seismic activity of the
Earth, FizikaZemli (in Russian), 7, 85-90.
[6] Zolotov O.V., Namgaladze A.A., Zkharenkova, I.E, Sha-
gimuratov, I.I. and Martynenko, O.V. (2010) Modeling of
ionospheric earthquake precursors generated by various
electric field sources. Natural Hazards Earth System
Sciences, 10, 7-18.
[7] Freund, F.T. (2007) Pre earthquake signals- Part I: De-
viatoric stresses turn rocks into a source of electric cur-
rents. Natural Hazards and Earth System Sciences, 7,
535-541.
[8] Freund, F.T. (2007) Pre earthquake signals—Part II:
Flow of battery currents in the crust. Natural Hazard
Earth System Sciences, 7, 543-548.
[9] Hermance, J.F. (1995) Electrical conductivity models of
the crust and mantle—Global Earth Physics. A Handbook
of Physical Constants, AGU Reference, Copyright 1995.
[10] Biagi, P.F., Piccolo, R., Ermini, A., Martelluci S., Bel-
lecci C., Hayakawa, M., Capozzi, V. and Kingsley, S.P.
(2001) Possible earthquakes precursors revealed by LF
radio signals. Natural Hazard and Earth System Sciences,
1, 99-104.
[11] Inan, U.S., Piddyachiy, D., Peter, W.B., Sauvaud, J.A.
and M-Demeter, P. (2007) Satellite observations of light-
ning induced precipitation. Geophysical Research Letters,
34, L07013.
[12] Gousheva, M.N., Georgiva, K.Y., Kirov, B.B. and
Atanssov, D. (2003) On the relation between solar activ-
ity and seismicity. Proceedings of International Confer-
ence on Recent Advances in Space Technologies, 20-22
November 2003.
[13] Qian, F. Y., Zhao, Y. L. and Lu, J. (1997) Georesistivity
precursors to the Tangshan earthquake. Annals of Geo-
physics, Annals of Geophysics, 40, 251-260.
[14] Fukao, Y., Koyama, T., Obayashi, M. and Utada, H.
(2004) Trans Pacific temperature field in the mantle tran-
sition region from seismic and electromagnetic tomo-
graphy. Earth and Planetary Science Letters, 217,
425-434.
[15] Bleckia, J.C., Parroth, M. and Wronowskia, R. (2010)
Plasma turbulence in the ionosphere prior to earthquakes
some remarks on the Demeter registrations. Journal of
Asian Earth Sciences, 41, 450-458.
[16] Akhoondzadeh, M. et al. (2010) Electron and ion density
variations before strong earthquakes. Natural Hazards
Earth System Sciences, 10, 7-18.
doi:10.5194/nhess-10-7-2010
[17] Mukherjee, S. (2008) Cosmic Influence on the Sun-Earth
Environment, Sensors, 8, 7736-7752.
[18] Namgaladze, A.A, Zolotov, O.V., Zakarenkhova, I.E.,
Shagimuratov, I.I. and Martynenko, O.V. (2009) Iono-
spheric total electron content variations observed before
earthquakes: Possible physical mechanism and modeling.
Proceedings of MSTU, 12, 308-315.
[19] Fraser-Smith, A.C., Bernardi, A., McGill, P.R, Ladd,
M.E., Helliwell, R.A. and Villard, O.G. (1990) Low-
Frequency magnetic field measurements near the epicen-
ter of the Ms 7.1 LomaPrieta Earthquake. Geophysics
Research Letters, 17, 1465-1468.
... The question here is why did actually those plates move? Some authors have attributed the reason earthquakes to the plate tectonic theory, and others attributed to the solar activity (Tavares and Azevedo 2011). A relationship between the occurrence dates of most of the strong earthquakes that have magnitude eight or more and solar activity (solar spots) has been demonstrated by Han et al. (2004) in China and western Mongolia. ...
... The closest planets to the sun are Mercury, followed by Venus, Earth, Mars Jupiter, Saturn, Uranus, Neptune and Pluto the farther away. Nowadays, the earthquakes and volcanic activity occur mainly along the plate boundary when they are rubbing against each other (Tavares and Azevedo 2011). The tidal phenomenon arises from the orbital motion of the moon around Earth and the axial rotation of the Earth around itself (Butikov 2002). ...
... The linking of reverse and strike slip faulting resulted in oblique convergence between the AP and CI is accommodated by the deformation distribution of both shortening and strike slip motion in the Zagros (Talebian and Jackson 2004). Previous studies did not show any significant correlation between the incidence of earthquakes and the semidiurnal tides according to the large earthquake records (Tavares and Azevedo 2011). The Earth's gravitational field is somewhat disturbed according to planetary positions relative to Earth. ...
Article
Full-text available
This research hypothesizes that tidal and earthquakes are induced by solar system planet positions, as the planetary attraction act as a trigger force change the speed of the Earth rotation. The occurrence of a sea tide is only a consequence of a relative slowdown of the rotational/revolving speed of the Earth which urges the Earth’s plates to move. The research included analyzing earthquake data for the whole Earth over July, 2019 with a case study of the Arabian Plate (AP) seismicity included the Zagros Folded Belt (ZFB) and Zagros Thrust Zone (ZTZ) as a seismic active belt in the northern hemisphere. The rotational velocity of the Earth has been calculated for eight seismic events, and it turns out that the velocity was different for each case. A negative proportional was found between earthquake and the Earth rotational speed. During the configuration of the Jupiter and Saturn in a straight line with the Earth over July 2019, one thousand and thirty-seven of earthquakes occurred around the world were statistically analyzed having 2–6 magnitudes. Rotational/ revolving speed, angular momentum and rotational inertia kinetic energy; gravitational potential energy of the Earth at equator and at 45 degrees were computed to show how rotational speed triggering plates. Planets interact with each other influencing earthquakes via the gravitational stresses arising from the configuration of the solar system planets that cause a slowdown of the rotational/revolving speed of the Earth. This stimulates the Earth’s plate to move generating earthquake due to the activation of faults.
... In addition, Simpson (1967) suggested that terrestrial solar flare effects which are actual coupling mechanisms which trigger quakes appear to be either abrupt acceleration in the earth's angular velocity or surge of telluric currents in the earth's crust. Furthermore, Gousheva et al. (2003) proposed that an obvious enhancement of earthquakes occurrence rate happened on the arrival day of high-speed solar wind and one day after it (Gousheva, 2003;Marilia, 2011). ...
... Since solar activity affects the earth globally, the analysis of seismic events should be on a global scale rather than focusing on a certain region (Marilia 2011, Yu 2010. To some extent, aftershocks cover up the statistical characteristics of the earthquake as individual events, so we select independent earthquakes to reduce occurrence rates of the earthquakes near source area from the aftershocks. ...
... The complicated relationship between Solar activity and the Earth once more is considered in this research. Our previous papers, [1][2][3] described the gravitational forces between the system of three bodies, Sun, Moon, Earth, and how variation between the Sun and Earth was almost a constant due to the dimension of each body. ...
... Our first results showed that the growth of earthquakes is not periodic, nor does it follow the growth Natural Science of sunspots during the twelve years of the solar cycle as previously studied. What has been observed was quasi-periodic increases in the tremors at deeper layers, developing independently of any external events [1][2][3]. Such a result would be linked to an internal structure in some areas that is currently unknown. ...
Article
Full-text available
We developed a statistical study analyzing the global seismicity enhancement and its variation along twenty years. X-flares sometimes occur in conjunction with Coronal Mass Ejections (CME) what made their connection with the Earth’s magnetosphere stronger. The preliminary study divided the Earth into seven regions determined by longitude and latitudes, and nine level depths valid for locations as Pacific area. The results showed that X beams influenced seismicity on terrestrial localities mainly magnitude earthquakes occurring below the crust at 70 km. These internal enhancements happen without the presence of any external forces such as studied in Solar Speed Winds. Nevertheless, those variations are perceptible in the presence of intense X flares and CME and less observed in the absent flares period. Two cases of high magnitude earthquakes last years are analyzed, and the extreme external conditions fitted with this theory. Keywords: Sun, Solar wind, Coronal Mass Ejections, X- flares, earthquakes
... The speculation that Sun influences Earth's seismic activity dates back to the 70s; 30 empirical evidence (both for and against it) has been presented recently. [31][32][33][34][35][36] Previous studies have focused on finding correlations (or the lack thereof) between solar activity and seismicity; however, it is important to note that correlation does not necessarily imply causality between the two phenomena. 37 Therefore, we investigated two questions, i.e., (i) is there any causal relationship between solar activity and Earth's seismicity? ...
Article
Full-text available
Despite the extensive literature related to earthquakes, an effective method to forecast and avoid occasional seismic hazards that cause substantial damage is lacking. The Sun has recently been identified as a potential precursor to earthquakes, although no causal relationship between its activity and the Earth’s seismicity has been established. This study was aimed at investigating whether such a relationship exists and whether it can be used to improve earthquake forecasting. The edit distances between earthquake point processes were combined with delay-coordinate distances for sunspot numbers. The comparison of these two indicated the existence of unidirectional causal coupling from solar activity to seismicity on Earth, and a radial basis function regressor showed accuracy improvements in the largest magnitude prediction of next days by 2.6%–17.9% in the odds ratio when sunspot distances were included.
... In addition to this most of the researchers strongly believe that solar flares are believed to cause increase in sea level and abruptly alter the Earth's spin causing earthquakes and volcanos. Thus, on simple terms these facts force every civil engineering structure to be more robust in design to avoid damages and provide uninterrupted service life [1,2]. ...
... Reference [11] found relationships between increased solar events during the last half of the twentieth century and the intensification of earthquake events. Reference [12] linked the maximum frequency of earthquakes during periods of moderate and high solar activity. ...
Article
Full-text available
Historical earthquakes registered in Chile (from 1900 up to 2015) with epicenters located between 17?30'S and 56?0'S latitude and yearly mean total sunspot number have been considered in order to evaluate a significant linkage between them. The occurrence of strong earthquakes along Chile and the sunspots activity are analyzed to inspect possible influence of solar cycles on earthquakes. The cross wavelet transform and wavelet coherence analysis were applied for sequences of sunspots and earthquakes activity. An 8 - 12 years modulation of earthquakes activity has been identified.
Article
In recent decades, ideas about earthquakes (EQ) have been formed as a final stage of a planetary continuous self-organizing tectonic process with periods of accumulation and relaxation of tectonic stresses. However, the scientific literature still presents studies of the response of atmospheric and ionospheric processes to individual strong EQs. In this paper, for the first time, the relationship between processes in the lithosphere, troposphere, and ionosphere is considered, taking into account new ideas about the seismic process as a global phenomenon and on the background of processes caused by space weather. Both planetary data (EQ, total electron content (TEC) of the ionosphere) and data (atmospheric pressure, critical frequency of the F2 layer of the ionosphere) of widely spaced observation points in the western and eastern hemispheres were used. To increase the reliability of statistical results, 4 independent databases of daily data for 2007–2015 were used. Stable effects of global seismic activity (GSA) in the considered parameters are established. Thus, the critical frequency of the F2 region with a sharp increase in the GSA increases by 0.4–0.5 MHz. This effect is quite stable and manifests itself almost simultaneously at ionospheric stations of the eastern and western hemispheres, as well as in planetary TEC values. At the same time, in the ionospheric variations, as before, the influence of both the troposphere (especially at a low level of solar activity) and space weather is traced, the characteristics of which in 75 % of cases also show an association with GSA. Therefore, space weather often but not always can act as a trigger on the EQs. In general, in the western hemisphere, the minimum atmospheric pressure occurs earlier than in the eastern, which leads to a noticeable increase in the pressure difference between the hemispheres by 10 mm. Hg., that indicates the relationship between global seismicity and global atmospheric circulation. The established GSA effects, as a rule, have the character of not a local short-term burst, but a jump followed by a gradual decrease (increase) of the index until the next active period (saw-toothed curve), i.e., the influence of the lithosphere on the overlying layers is continuous and is cyclical in nature, probably due to the cyclical nature of tectonic processes. Most likely, several different couplings between geospheres are realized at the same time, partially synchronized by changes in space weather, which requires new physical mechanisms to explain them.
Article
A possible relationship between solar activity and the seismic activity of the Earth is considered. We analyzed the frequency of occurrence of earthquakes of various magnitudes with the Fourier transform: for M ≥ 7 over the period 1900—2019 and for 2.5 ≤ M ≤ 7 over the period 1973–2019. The average annual, monthly, and daily values of the solar-terrestrial variables, the number of earthquakes with intensities that fall within the specified boundaries are calculated. The epoch overlapping method was used to analyze the possible relationship between the Wolf numbers and the number of earthquakes at the corresponding moment in the cycle. 4 periods of each solar cycle were identified: the phase of ascending, maximum, descending, and minimum. Earthquakes over the entire globe and in the regions of extension and compression of the earth's crust were analyzed for each phase. No statistically significant dependencies between solar-terrestrial variables and earthquake initiation were found for all time intervals and all selected earthquake magnitudes. An interesting fact was established concerning the change in the number of earthquakes at different periods of the day. The number of earthquakes in the nighttime appreciably increases (by ~ 10 %) compared to the daytime. A slight increase in the number of earthquakes after local noon was also detected. We could not confirm the existence of a direct connection between solar activity and the seismic activity of the Earth, but we cannot also claim that such a connection does not exist.
Conference Paper
Exogenous parameter is basically referred to the external activities that may have been the important factors in modulating the atmosphere, ionosphere and the earth's surface. Due to its significant impacts, there is possibility to link solar activities and seismicity. Associated investigations have been done by previous researchers in order to explore the solar — terrestrial connection; nevertheless, the physical mechanism is still controversial. To comprehend the investigation of this coupling mechanism, we propose another exogenous source to be analyzed which is cosmic ray. As solar activity, cosmic ray also has minimum and maximum phases or called as cosmic ray cycle, but it is anti-correlation between phases of sunspot and cosmic ray cycles. In this brief report, we examine the trend of shallow earthquake occurrence as the caused effect during recent 4 complete solar cycles (SC 20–23) in order to study its possible link to sun spot number (SSN). The earthquakes were categorized into very shallow earthquakes with epicenter depth less than 35 km and deeper earthquakes with epicenter depth between 35–70 km. For very shallow earthquakes, the analysis shows two interesting features. First, its occurrence rate shows a steady increase during the 40 years period of 1964–2005, with average increase rate about 150/year. Second, a distinct increase of the occurrence rate occurs during each solar minimum of SC 21–23. Neither of these features is found in the earthquakes with deeper epicenters, suggesting that the solar influence on seismicity, if exists, is likely to exist only in the case of very shallow earthquakes whose epicenter is in the crust region.
Article
The paper presents the variation of variable component of coronal index for two period 1950–1962 and 1963–2014 and its association with major earthquakes (magnitude ≥6.0 Richter scale) for the same two periods is also offered. Analysis shows that frequency of major earthquake increases with the decrease in variable component of coronal index and vice versa. Possible explanation is also presented.
Article
Full-text available
1] DEMETER spacecraft detects short bursts of lightning-induced electron precipitation (LEP) simultaneously with newly-injected upgoing whistlers, and sometimes also with once-reflected (from conjugate hemisphere) whistlers. For the first time causative lightning discharges are definitively geo-located for some LEP bursts aboard a satellite. The LEP bursts occur within <1 s of the causative lightning and consist of 100– 300 keV electrons. First in-situ observations of large regions of enhanced background precipitation are presented. The regions are apparently produced and maintained by high rate of lightning within a localized thunderstorm.
Article
Full-text available
This paper studies the relationship between solar activity and big earthquakes (Ms≥8) that occurred in China and western Mongolia. It is discovered that the occurrence dates of most of the big earthquakes in and near faults with west-east strike are close to the maximum years of sunspot numbers, whereas dates of some big earthquakes which are not in such faults are not close to the maximum years. We consider that it is possibly because of the appearance of many magnetic storms in the maximum years of solar activity. The magnetic storms result in anomalies of geomagnetic field and then produce eddy current in the faults gestating earthquake with near west-east strike. Perhaps the gestated big earthquakes occur easily since the eddy current heats the rocks in the faults and therefore decreases the shear resistant intensity and the static friction limit of the rocks.
Article
Full-text available
The GPS derived anomalous TEC disturbances before earthquakes were discovered in the last years using global and regional TEC maps, measurements over individual stations as well as measurements along individual GPS satellite passes. For strong mid-latitudinal earthquakes the seismo-ionospheric anomalies look like local TEC enhancements or decreases located in the vicinity of the forthcoming earthquake epicenter In case of strong low-latitudinal earthquakes there are effects related with the modification of the equatorial F2-region anomaly: deepening or filling of the ionospheric electron density trough over the magnetic equator. We consider that the most probable reason of the NmF2 and TEC disturbances observed before the earthquakes is the vertical drift of the F2-region ionospheric plasma under the influence of the zonal electric field of seismic origin. To check this hypothesis, the model calculations have been carried out with the use of the Upper Atmosphere Model. The electric potential distribution at the near-epicenter region boundary required for the electric field maintenance has been proposed. The upper atmosphere state, presumably foregone a strong earthquake, has been modeled. The results of the corresponding numerical model calculations have revealed a fine agreement with TEC anomalies observed before strong earthquakes at the middle and low latitudes both in spatial scales and in amplitude characteristics. Comment: 8 pages, 6 figures, http://vestnik.mstu.edu.ru/v12_2_n35/articles/22_namgal.pdf
Article
Full-text available
Using IAP (plasma analyzer) and ISL (Langmuir probe) experiments onboard DEMETER (Detection of Electromagnetic Emissions Transmitted from Earthquake Regions) satellite and GPS (Global Positioning System) measurements, we have statistically analyzed the variations of the electron and ion densities to search for disturbances in the vicinity of four large earthquakes prior to events. The indices D <sub>st</sub> and K <sub>p</sub> were used to distinguish pre-earthquake anomalies from the other anomalies related to the geomagnetic activities. For each studied case, a very good agreement was found between the different parameters estimated by DEMETER and GPS data in the detection of pre-seismic anomalies. Our statistics results show that the anomalous deviations prior to earthquakes have different sign from case to case, and that their amplitude depends on the magnitude of the earthquake. It has also been found that the electron density measured by the ISL experiment at night detects anomalous variations significantly before the earthquakes. The appearance of positive and negative anomalies in both of DEMETER and TEC (Total Electron Content) data during 1 to 5 days before all studied earthquakes during quiet geomagnetic conditions indicates that these anomalous behaviors are highly regarded as seismo-ionospheric precursors.
Article
The authors report the results of measurements of low frequency magnetic noise by two independent monitoring systems prior to the occurrence of the M{sub s} 7.1 Loma Prieta earthquake of 17 October 1989. Their measurements cover 25 narrow frequency bands in the more than six-decade frequency range 0.01 Hz-32 kHz, with a time resolution varying from a half hour in the ULF range (0.01-10 Hz) to one second in the ELF/VLF range (10 Hz-32 kHz). The ULF system is located near Corralitos, about 7 km from the epicenter. The ELF/VLF system is located on the Stanford campus, about 52 km from the epicenter. Analysis of the ELF/VLF system is located on the Stanford campus, about 52 km from the epicenter. Analysis of the ELF/VLF data has revealed no precursor activity that they can identify at this time. However, the ULF data have some distinctive and anomalous features. First, a narrow-band signal appeared in the range 0.05-0.2 Hz around September 12 and persisted until the appearance of the second anomalous feature, which consisted of a substantial increase in the noise background starting on 5 October and covering almost the entire frequency range of the ULF system. Third, there was an anomalous dip in the noise background in the range 0.2-5 Hz, starting one day ahead of the earthquake. Finally, and perhaps most compelling, there was an increase to an exceptionally high level of activity in the range 0.01-0.5 Hz starting approximately three hours before the earthquake. There do not appear to have been any magnetic field fluctuations originating in the upper atmosphere that can account for this increase. Further, while the systems are sensitive to motion, seismic measurements indicate that there were no significant shocks preceding the quake. Thus, the various anomalous features in the data, and in particular the large-amplitude increase in activity starting three hours before the quake, may have been magnetic precursors.
a b s t r a c t The question about presence of some precursors of the earthquakes has a long history. The answer is still not resolved, but researchers are looking for the effects which can be registered prior to earthquakes. One of the factors which has been found is the variation of the electromagnetic field observed on ground as well as onboard satellites. The disturbances of the electromagnetic field around areas of the earthquakes as pre-seismic events can occur few hours or even few days before the main shock. The payload of the DEMETER French microsatellite allows to measure waves and also some important plasma parameters (ion composition, electron density and temperature, energetic particles) with high temporal resolution in the ionosphere over the seismic regions. In the present work, analysis of the low frequency fluctuations of the electric fields for selected strong earthquakes in Japan (2004), China (2008), Taiwan (2006) and New Zealand (2009) are given. Special attention will be given to the study of the spectral characteristics of these variations and the search for nonlinear effects. This analysis is possible in the time interval where the waveform has been transmitted. The mechanism of the energy transmission from earthquakes to the ionosphere is not clear, but we can discuss the behavior of the ionospheric plasma and the search for instabilities which could be a source of electromagnetic field variations. A brief discussion of the charac-teristics of the spectra and multi-spectra is given in this paper. Attention is particularly given to the effect prior to the earthquake in New Zealand, when a nonlinear interaction leading to a lower hybrid wave generation was directly seen.
Article
An 11-y modulation of large Italian earthquakes has been successfully identified and found to be positively linked to sunspot activity. The seismic activity appears to be modulated by the 11-y sunspot cycle through the coherent variation of geomagnetic activity. It is proposed that the two phenomena are linked by the influence of a magnetostriction process on stresses in the crust. An implication of this model is that geomagnetic storms may directly trigger large earthquakes. L'analisi dei valori annuali delle macchie solari, della variazione geomagnetica interdiurna e dei grossi terremoti italiani ha permesso di identificare una significativa diretta modulazione undecennale dell'attività sismica da parte dell'attività solare attraverso la coerente variazione dell'attività geomagnetica con un relativo effetto magnetostrittivo sulle rocce crostali. Il modello proposto si rivela di pratica importanza per la previsione dei terremoti innescati da tempeste magnetiche.
Article
The trans-Pacific temperature field for the depth range 350–850 km was inferred from global seismic tomography and semi-global electromagnetic tomography. The seismic tomography incorporated millions of reported first arrival times and 7000 PP–P differential travel times measured on broadband seismograms. The electromagnetic tomography used voltage data from trans-Pacific submarine cables and magnetic field data from circum-Pacific geomagnetic observatories. The resultant P-wave velocity anomalies and electrical conductivity anomalies were converted to temperature anomalies using a proposed conversion formula and experimental results for mantle minerals, respectively. These conversions show consistently high-temperature anomalies of 200–300 K in the mantle transition region beneath the Hawaiian hotspot. At subduction zones, where slab-related cold anomalies and wedge mantle-related hot anomalies are likely to coexist in close proximity, the seismic and electromagnetic tomography did not always give consistent features, in part because of the preferred sensitivity of electromagnetic tomography to hot anomalies. Low-temperature anomalies of 200–300 K associated with subducted slabs are clearly resolved in the seismic tomography, but are less apparent in the electromagnetic tomography. The high-temperature anomaly in the intervening zone between the Mariana and Philippine slabs is very pronounced in the electromagnetic tomography but is marginal in the seismic tomography.
Article
We applied a tomographic method to image an aseismic strike–slip fault in North Morocco and found that the occurrence of earthquakes is not only controlled by the state of tectonic stress but also by material heterogeneity in the crust. We have constructed an integrated model of seismic, electric, magnetic and heat flow properties across northeastern Morocco primarily based on a tomography inversion of local earthquake arrival times. The seismic images obtained show a pronounced low-velocity zone at 5 km depth parallels to the Nekor fault, coinciding with an anomalously high conductive and low gravity structure, which is interpreted as a fault gouge zone and/or a fluid-filled subsurface rock matrix. Below 10 km depth, a weak positive velocity zone indicates that the fault gouge is stable. The seismicity and the seismic velocity results for the Al-Hoceimas region show that the concentrations of earthquakes are confined in the high velocity area. This anomaly is interpreted to be a brittle and competent layer of the upper crust that sustains seismogenic stress. On the eastern coast line of Morocco, we infer that a high density, high velocity body exists in the shallowest layers of the upper crust, probably formed by Miocene volcanic rocks.