The Eastern North American Margin Community Seismic Experiment: An Amphibious Active‐ and Passive‐Source Dataset

Abstract

The eastern North American margin community seismic experiment (ENAM‐CSE) was conceived to target the ENAM Geodynamic Processes at Rifting and Subducting Margins (GeoPRISMS) primary site with a suite of both active‐ and passive‐source seismic data that would shed light on the processes associated with rift initiation and evolution. To fully understand the ENAM, it was necessary to acquire a seismic dataset that was both amphibious, spanning the passive margin from the continental interior onto the oceanic portion of the North American plate, and multiresolution, enabling imaging of the sediments, crust, and mantle lithosphere. The ENAM‐CSE datasets were collected on‐ and offshore of North Carolina and Virginia over a series of cruises and land‐based deployments between April 2014 and June 2015. The passive‐source component of the ENAM‐CSE included 30 broadband ocean‐bottom seismometers (OBSs) and 3 onshore broadband instruments. The broadband stations were deployed contemporaneously with those of the easternmost EarthScope Transportable Array creating a trans‐margin amphibious seismic dataset. The active‐source portion of the ENAM‐CSE included several components: (1) two onshore wide‐angle seismic profiles where explosive shots were recorded on closely spaced geophones; (2) four major offshore wide‐angle seismic profiles acquired with an airgun source and short‐period OBSs (SPOBSs), two of which were extended onland by deployments of short‐period seismometers; (3) marine multichannel seismic (MCS) data acquired along the four lines of SPOBSs and a series of other profiles along and across the margin. During the cruises, magnetic, gravity, and bathymetric data were also collected along all MCS profiles. All of the ENAM‐CSE products were made publicly available shortly after acquisition, ensuring unfettered community access to this unique dataset.

Full text

The Eastern North American
Margin Community Seismic
Experiment: An Amphibious
Active- and Passive-Source Dataset
Colton Lynner*1, Harm J. A. Van Avendonk2, Anne Bécel3, Gail L. Christeson2,
Brandon Dugan4, James B. Gaherty3, Steven Harder5, Matthew J. Hornbach6,
Daniel Lizarralde7, Maureen D. Long8, M. Beatrice Magnani6, Donna J. Shillington3,
Kasey Aderhold9, Zachary C. Eilon10, and Lara S. Wagner11
Abstract
Cite this article as Lynner, C., H. J. A.
Van Avendonk, A. Bécel, G. L. Christeson,
B. Dugan, J. B. Gaherty, S. Harder,
M. J. Hornbach, D. Lizarralde, M. D. Long,
et al. (2019). The Eastern North American
Margin Community Seismic Experiment:
An Amphibious Active- and Passive-Source
Dataset, Seismol. Res. Lett. 91, 533–540,
doi: 10.1785/0220190142.
Supplemental Material
The eastern North American margin community seismicexperiment (ENAM-CSE) was con-
ceived to target the ENAM Geodynamic Processes at Rifting and Subducting Margins
(GeoPRISMS) primary site with a suite of both active- and passive-source seismic data
that would shed light on the processes associated with rift initiation and evolution. To
fully understand the ENAM, it was necessary to acquire a seismic dataset that was both
amphibious, spanning the passive margin from the continental interior onto the oceanic
portion of the North American plate, and multiresolution, enabling imaging of the sedi-
ments, crust, and mantle lithosphere. The ENAM-CSE datasets were collected on- and off-
shore of North Carolina and Virginia over a series of cruises and land-based deployments
between April 2014 and June 2015. The passive-source component of the ENAM-CSE
included 30 broadband ocean-bottom seismometers (OBSs) and 3 onshore broadband
instruments. The broadband stations were deployed contemporaneously with those
of the easternmost EarthScope Transportable Array creating a trans-margin amphibious
seismic dataset. The active-source portion of the ENAM-CSE included several components:
(1) two onshore wide-angle seismic profiles where explosive shots were recorded on
closely spaced geophones; (2) four major offshore wide-angle seismic profiles acquired
with an airgun source and short-period OBSs (SPOBSs), two of which were extended
onland by deployments of short-period seismometers; (3) marine multichannel seismic
(MCS) data acquired along the four lines of SPOBSs and a series of other profiles along
and across the margin. During the cruises, magnetic, gravity, and bathymetric data were
also collected along all MCS profiles. All of the ENAM-CSE products were made publicly
available shortly after acquisition, ensuring unfettered community access to this unique
dataset.
Introduction
The eastern North American margin (ENAM) represents a
type-locale of a magma-rich passive rifted margin. Continental
extension started as early as the Middle Triassic by reactivation
of Paleozoic structures of the Appalachian orogen (Withjack
et al.,1998;Thomas, 2006). At the Triassic-Jurassic boundary
(∼200 Ma), a short-lived magmatic pulse, the Central Atlantic
Magmatic Province, emplaced magmatism over a large region
spanning parts of North America, Europe, South America,
and Africa (Marzoli et al.,2018), including in the oldest land-
ward rift basins of the ENAM (Schlische, 2003). The breakup
of Pangaea and subsequent onset of Atlantic Ocean seafloor
1. Department of Earth Sciences, University of Delaware, Newark, Delaware U.S.A.;
2. Institute for Geophysics, University of Texas, Austin, Texas, U.S.A.; 3. Lamont–
Doherty Earth Observatory, Columbia University, Palisades, New York, U.S.A.;
4. Department of Geophysics, Colorado School of Mines, Golden, Colorado, U.S.A.;
5. Department of Geological Sciences, University of Texas at El Paso, El Paso, Texas,
U.S.A.; 6. Huffington Department of Earth Sciences, Southern Methodist University,
Dallas, Texas, U.S.A.; 7. Department of Geology and Geophysics, Woods Hole
Oceanographic Institution, Woods Hole, Massachusetts, U.S.A.; 8. Department of
Geology and Geophysics, Yale University, New Haven, Connecticut, U.S.A.;
9. Incorporated Research Institutions for Seismology, Washington, D.C., U.S.A.;
10. Department of Earth Science, University of California Santa Barbara, Santa
Barbara, California, U.S.A.; 11. Department of Terrestrial Magnetism, Carnegie
Institution for Science, Washington, D.C., U.S.A.
*Corresponding author: clynner@udel.edu
© Seismological Society of America
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spreading is marked by a few prominent coast-parallel magnetic
anomalies, though their ages are not precisely known (e.g.,
Greene et al.,2017). In particular, the prominent East Coast
magnetic anomaly occurs at the rifted margin and is interpreted
to represent synrift volcanism (e.g., Alsop and Talwani, 1984).
Other evidence for magmatic rifting comes from imaging of sea-
ward-dipping reflectors interpreted as subaerial volcanism (e.g.,
Oh et al., 1995) and high-velocity lower crust interpreted as
mafic magmatic intrusions and underplating (e.g., Tréhu et al.,
1989;Holbrook et al.,1994). Long-term subsidence and sedi-
mentation shaped the present-day margin (Dillon and Popenoe,
1988). High-resolution images of landslide deposits on the
continental shelf and slope of the eastern United States
(Twichell et al., 2009) show that the margin is still a dynamic
environment.
Deliberations that led to the eastern North American margin
community seismic experiment (ENAM-CSE) began at a joint
Geodynamic Processes at Rifting and Subducting Margins
(GeoPRISMS) and EarthScope ENAM implementation work-
shop held at Lehigh University in October 2011. Meeting par-
ticipants from the GeoPRISMS and EarthScope communities
proposed a wide range of science targets. There was broad con-
sensus that an important avenue for discovery was the explora-
tion of linkages between mantle, crustal, and surficial processes
that span spatial scales and include the onshore and offshore
parts of the margin. It was concluded that the design of the
CSE should include: (1) a suite of seismic datasets in a nested
experimental design that incorporates different resolution length
scales, (2) a broadband ocean-bottom seismometer (OBS)
deployment to complement the EarthScope Transportable
Array (TA) seismic stations, and (3) data acquisition in a
well-chosen section of the margin, such that integration of these
data sets would naturally follow.
After gathering more community input on the CSE design at
the Fall 2011 AGU meeting and through an online poll hosted
by GeoPRISMS, the area around Cape Hatteras was chosen for
data acquisition. The experiment plan would include active- and
passive-source seismic data acquisition at stations both onshore
and offshore. The GeoPRISMS program would fund the gather-
ing of these new datasets with the project lead by a large team of
scientists from many institutions: (1) the University of Texas at
Austin Institute for Geophysics, (2) the Center for Earthquake
Research and Information at the University of Memphis,
(3) The College of New Jersey, (4) Lamont–Doherty Earth
Observatory of Columbia University, (5) Rice University,
(6) Southern Methodist University, (7) University of Texas at
El Paso, (8) Woods Hole Oceanographic Institution (WHOI),
and (9) Yale University. Graduate students and early-career sci-
entists from the broader geosciences community were invited to
participate in the data acquisition through a formal application
process. In total, 79 scientists and students from 49 different
institutions participated in ENAM-CSE-related fieldwork.
Involving so many participants and institutions served to engage
a broad community, provide educational opportunities, and
create an investment in the ENAM-CSE dataset.
Data Collection
The ENAM-CSE study area is located in, and offshore of,
North Carolina and Virginia in the United States (Fig. 1).
The ENAM-CSE collected passive- and active-source, broad-
band, and short-period seismic data. The broadband deploy-
ment specifically related to the ENAM-CSE comprised three
stations installed at schools along the Outer Banks of North
Carolina and 30 OBS instruments from the U.S. Ocean Bottom
Seismic Instrument Pool (OBSIP). Because the EarthScope TA
had already reached the east coast, combining the TA and
ENAM-CSE provides a contemporaneous broadband dataset
that spans from the Appalachian Mountains to the Atlantic
sea floor.
The broadband array of the ENAM-CSE recorded data
from April 2014 to June 2015 (Gaherty et al., 2014). The three
Outer Banks stations were direct-buried Nanometrics Trillium
Compact seismometers from the Incorporated Research
Institutions for Seismology–Program for the Array Seismic
Studies of the Continental Lithosphere (IRIS-PASSCAL)
instrument pool with 120 s corner frequencies recording at
both 1 and 50 samples per second. These stations are located
between 1 and 3 m above sea level along the coast. The 30 OBS
stations were provided by OBSIP Institutional Instrument
Contributor (IIC) WHOI and use Güralp CMG3T sensors,
with 120 s corner frequencies. The broadband OBS instru-
ments recorded data at 1 and 100 samples per second and were
equipped with differential pressure gauges with sample rates
of 20 samples per second. They were deployed in water depths
of ∼1300 to ∼5300 m. Example broadband data from the
ENAM-CSE and regional TA stations are shown in Figure 2.
OBS instruments were deployed and recovered by the R/V
Endeavor with a 100% station recovery rate. Station locations
on the seafloor were determined using a roughly circular acous-
tic survey performed immediately following deployment.
Instruments deployed in the Gulf Stream were observed to drift
a substantial horizontal distance as they fell through the water
column (Fig. S1, available in the supplemental material to this
article). The average drift was 800 m (in average water depth of
∼3400 m), but some stations drifted more than a kilometer,
with the maximum drift being ∼2060 m. The dominant
drift direction was north-northeast, consistent with the Gulf
Stream, with stations closest to the shore showing the strongest
drifts.
Active-source data acquisition for the ENAM-CSE started in
September 2014 with a two-ship experiment off Cape Hatteras.
Four major seismic reflection/refraction lines composed of short-
period OBS (SPOBS) stations and additional marine multichan-
nel seismic (MCS) reflection lines were acquired with the R/V
Marcus G. Langseth, while the ENAM-CSE broadband array
was recording (Fig. 1). The experiment plan included 94
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SPOBS stations on two margin crossing and two margin parallel
lines. Twenty-four of these instruments were brought on board
the R/V Endeavor from the OBSIP IIC Scripps Institution of
Oceanography (SIO), and 23 SPOBSs were contributed by
OBSIP IIC WHOI. Each of these 47 instruments were deployed
twice to cover the four marine seismic transects (Van Avendonk
et al.,2014,2015). First, the southernmost and easternmost lines
were deployed from the R/V Endeavor, whereas the R/V Marcus
G. Langseth produced airgun shots and collected MCS data
(Fig. 1). The SPOBS instruments were then recovered and rede-
ployed along the northernmost and westernmost lines, where the
R/V Marcus G. Langseth again produced shots and collected MCS
data. WHOI stations used Geospace GS-11D three-component
geophones that recorded at 1 and 200 samples per second. SIO
stations employed Sercel L-28 LB geophones that recorded data
at 200 samples per second.
Both the SIO and WHOI
stations used High Tech, Inc.
HTI-90-U hydrophones for
pressure measurements. The
SPOBSs were deployed in water
depths of ∼30to ∼5200 m.
Similar to the broadband sta-
tions, the SPOBSs showed drift
consistent with the Gulf Stream.
All but one of the SPOBS instru-
ments was recovered for a
recovery rate of 98.9%.
Over ∼4800 km of marine
MCS data were collected
aboard the R/V Marcus G.
Langseth between September
and October 2014 (expedition
MGL1408; Shillington et al.,
2014a). Different acquisition
configurations were used
depending on the depth of the
science targets. MCS transects
coincident with the SPOBS lines
were acquired using a 36-
element, four-string, 6600 cubic
inch tuned airgun array towed
at a depth of 9 m to maximize
low-frequency energy and deep
imaging. Data were recorded
on a 636-channel, 8-km-long
streamer towed at 9 m with a
sample rate of 2 ms and a rec-
ord length of 18.432 s. The shot
interval was 50 m with the
streamer group spacing at
12.5 m. For part of the south-
ernmost and westernmost lines,
streamer depth was deepened to reduce swell noise. In addition,
for part of the westernmost line, shot spacing was increased to
62.5–75 m to maintain an 18.432 s record. An example of MCS
data along the easternmost SPOBS line is shown in Figure 3.
MCS transects not coincident with the SPOBS lines used a
smaller 3300 cubic inch, 18-element, two-string tuned airgun
array. Deeper water lines were recorded on the 636 channel,
8 km long streamer with the same sample rate, record length,
shot interval, and streamer group spacing, as described earlier.
Shallow water lines, those along the shelf and upper slope, were
acquired with a 480-channel, 6-km-long streamer. The sam-
pling rate for the shallow lines was 1 ms, the record length
was 9 s, the receiver group spacing was 12.5 m, and the shot
interval was 25 m. The source and the streamer for all of the
non-SPOBS coincident lines were towed at a depth of 6 m to
32°
34°
36°
38°
Bathymetry (km)
0–2.5–5.0 2.5
32°
34°
36°
38°
–81° –79° –75° –73°–77° –71°
–81° –79° –75° –73°–77° –71°
Onshore instrument
OBS instrument
TA broadband
ENAM broadband
ENAM short period
Onland shot
Offshore shots
Figure 1. Station map of the eastern North American margin community seismic experiment
(ENAM-CSE) plotted on top of bathymetry. Broadband ocean-bottom seismometer (OBS) seismic
stations are shown as red circles, broadband Outer Banks stations as red triangles, short-period
OBS (SPOBS) stations as yellow circles, three-component short-period land stations as yellow
triangles, one-component short-period land stations as gold triangles, land-based shots as pink
stars, and multichannel seismic (MCS) lines as pink lines. Gravity, magnetic, and bathymetry data
were collected along the MCS lines. Transportable Array (TA) stations are shown as blue triangles.
The color version of this figure is available only in the electronic edition.
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record high-frequency energy and provide fine-scale imaging
of the sedimentary layers.
In addition to seismic data, the R/V Marcus G. Langseth
collected a suite of other geophysical observables including
multibeam bathymetry, sub-bottom profiler, magnetic, gravity,
and expendable bathythermograph (XBT) data. Multibeam
bathymetry and sub-bottom profiler data were acquired
throughout the entire cruise except on transits to and from
Norfolk. Multibeam data were acquired with the onboard
Simrad-Kongsberg EM122/SB122 system; 3.5 kHz sub-bottom
profiler data were recorded with a Knudsen 3260 Echosounder
system. Total field magnetic data were recorded throughout the
cruise, except on transits to and from Norfolk and for brief
power downs for maintenance and streamer recovery. Magnetic
data were acquired with a Geometrics G-882 Cesium marine
magnetometer system that was towed 116 m behind the ship.
Gravity data were collected with a Bell Aerospace BGM-3
air-sea gravimeter. XBTs were deployed on most of the MCS
lines. One hundred and forty-nine XBTs and four expendable
conductivity-temperature-depth probes were deployed during
the cruise.
The September and October 2014 onshore active-source
component of the ENAM-CSE consisted of 80 short-period
three-component Sercel L28 instruments recording at 250
samples per second on RefTek RT130s to capture offshore air-
gun shots (Magnani and Lizarralde, 2014). These instruments
were provided by the IRIS-PASSCAL instrument center. The
stations were arranged along two margin perpendicular lines
in a continuation of the offshore SPOBS lines (Fig. 1). The
onshore recordings of airgun shots form a very large amphibi-
ous data volume spanning the entire margin, because all land
stations were deployed for the duration of R/V Marcus G.
Langseth cruise MGL1408. The onshore–offshore data (Magnani,
Van Avendonk, et al.,2015) are of variable quality, as noise levels
varied significantly between day and night and between onshore
sites.
A second onshore seismic experiment took place in June
2015 (Magnani, Lizarralde, and Harder, 2015;Magnani et al.,
2018). Roughly 800 vertical-component Geospace GS11D
instruments with RefTek RT125A recorders (commonly known
as Texans) recorded at 250 samples per second. These instru-
ments were provided by the IRIS-PASSCAL instrument center
and installed in two phases along the same transects that were
6
8
10
12
Two way travel time (s)
Moho?
North South
Moho?
Thick oceanic crust
Seafloor
~3 km of sediment
Upper mantle
Structures in the crust
20 km
Top of crust
Figure 3. Example of shipboard time migration of MCS data
acquired along the easternmost SPOBS line on the R/V Marcus G.
Langseth. Prominent reflections highlight a ∼3 km thick
sedimentary layer, thick oceanic crust, and several internal crustal
reflectors. The color version of this figure is available only in the
electronic edition.
PSSS Rayleigh
800 1200 1600 2000 2400
Time (s)
8400
8600
8200
Distance (km)
ENAM-CSE TA
Figure 2. Vertical-component record section of the 9 October
2014 Mw7.0 East Pacific Rise seismic event from the ENAM-CSE
(blue lines) and TA (black lines) broadband seismic stations.
Waveforms have been filtered between 10 and 100 s. Even
without tilt or compliance corrections, the ENAM-CSE OBS sta-
tions show several clear arrivals. SS, seismic phase. The color
version of this figure is available only in the electronic edition.
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used in the 2014 onshore–offshore field campaign (Fig. 1). They
were first deployed along the southern ENAM-CSE line then
along the northern line. A total of 11 land-based 182 kg shots,
provided by the U.S. National Science Foundation (NSF)-
funded seismic source facility at University of Texas El Paso,
were recorded by the Texan array, five shots along the northern
line and six shots along the southern line. An example of the
explosion seismic data (Fig. 4) shows very clear deep-crustal
and mantle seismic refractions.
Data Quality and
Availability
All of the ENAM-CSE data
were intended to become
immediately publicly available.
The broadband OBS data had
a brief distribution delay, need-
ing to be first reviewed, filtered,
and redacted by the U.S. Navy.
The onshore-offshore broad-
band data and the SPOBS
data are available through the
IRIS Data Management Center
(DMC) under the network code
YO (Gaherty et al.,2014)
in miniSEED format. The
redacted OBS data are archived
under HH? channels, and the
continuous data filtered above
3 Hz are archived under HX?
channels. Continuous redacted
1 sample per second data are
archived under LH? channels.
Data return for the broadband
OBSs was 98.6% with an addi-
tional 6.6% redacted by the U.S.
Navy on the unfiltered channels
(Figs. S2 and S3). The onshore
active-source data can be
accessed via the IRIS-DMC
under network code ZI
(Magnani and Lizarralde, 2014;
Magnani, Lizarralde, and
Harder, 2015)andarestoredin
PH5 format. It is also available
through the Interdisciplinary
Earth Data Alliance (IEDA)
(Magnani, Van Avendonk, et al.,
2015;Magnani et al., 2018).
The MCS data collected by the
R/V Marcus G. Langseth can
be accessed via the Marine
Geoscience Data System
(MGDS) in several forms
(Shillington et al., 2014a,2018;Van Avendonk et al., 2014,
2015). All of the underway geophysical data collected aboard
the R/V Marcus G. Langseth are also accessible through the
MGDS under cruise MGL1408 (Shillington et al.,2014b).
Amphibious short-period data can also be accessed through
the MGDS (Magnani, Lizarralde, and Harder, 2015).
The overall data quality of the ENAM-CSE is good. The
percent data availability, as calculated by Modular Utility for
STAtistical kNowledge Gathering (MUSTANG) (Casey et al.,
119 74 2 9 16 61 106 150 196 240
Distance (km)
10
(a)
(b) (c)
8
6
4
2
0
South North
Vertical
OBS 307
ww
Time (s), reduced by 7 km/s
Pg
Pg
Pg
Pn
Pn
PmP
Northern Line
PmP
PmP
Pg
Pg
Pn
Explosive shot 11
Northern line
Onshore
station 206
040801201602006080100120140
Distance (km)Distance (km)
Time (s), reduced by 7 km/s
8
6
4
2
0
West WestEast East
Figure 4. Example refraction data from the short-period stations. (a) Vertical channel of OBS 307
recording airgun shots from the R/V Marcus G. Langseth along the easternmost SPOBS line.
(b) Example of the ENAM onshore–offshore seismic refraction data. Airgun shots of the R/V Marcus
G. Langseth along the southernmost line recorded on land station 206. (c) Example of the 2015
ENAM land explosion refraction experiment. Texans recorded data from explosion 11 along the
southern line. The time axis is reduced at 7 km=s for all three plots. Pg is P-wave turning in crust,
PmP is wide-angle Moho reflection, Pn is mantle refraction, ww is the water wave. The color
version of this figure is available only in the electronic edition.
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2018), was ∼98% for the YO network (Fig. S2). A significant por-
tion of the ENAM-CSE study region encompasses an area
impacted by the Gulf Stream. As such, the OBS data have high
levels of noise (Fig. 5,Figs.S4andS5).TheOBSinstrumentsalso
exhibit depth-dependent noise characteristics, such that shal-
lowerstationshaveslightlyhighernoiselevelsthandeeperwater
stations. A few of the SPOBS instruments exhibit an anomalous
peak in noise at ∼6 Hz that warrants further study. The Gulf
Stream also impacted the MCS data acquisition by creating sig-
nificant streamer feathering.
A few stations had issues with significant noise or problem-
atic seismic components. Broadband OBS station C01 had
excessive amounts of noise on the vertical component, possibly
brought on by leveling issues. Station B01 returned bad seismic
channels. A few SPOBS stations also experienced excessive
noise levels and/or issues with seismic components. All
ENAM-CSE stations with known issues can be found in
Table T1. We caution future users of the ENAM-CSE dataset
when using data from any of the potentially problematic sta-
tions. Inherent to the deployment of OBS instruments is the
lack of initial station orientation information. The broadband
OBS stations have had their orientations calculated by Lynner
and Bodmer (2017). Orientations for the SPOBS stations have
not yet been calculated.
Initial Observations
A major part of the ENAM-CSE was outreach and inclusion of
participants from the broader community. In addition to the
extensive field participation described earlier, in May and June
2015, as part of the ENAM-CSE, week-long OBS and MCS
processing workshops were held at University of Texas
Institute for Geophysics and at the Lamont–Doherty Earth
Observatory of Columbia University, respectively. The goal of
these workshops was to introduce students and early career sci-
entists to analysis of active-source seismic data. In the refraction
workshop, participants learned to plot data, pick arrivals, build a
starting model, carry out tomographic inversions, and analyze
results. In the reflection workshop, each participant processed
one of the reflection profiles from raw shot gathers to a time-
migrated image.
Summary
The ENAM-CSE was derived from a community desire for a
margin crossing amphibious dataset that could address science
questions from the GeoPRISMS rift initiation and evolution
initiative at a variety of scales. Timed to leverage the presence
of TA stations along the east coast, 30 OBS and three coastal
broadband stations were deployed for ∼1 year, creating a con-
tinuous amphibious broadband seismic dataset that spans
from the Appalachian Mountains to Atlantic seafloor. The
short-period data acquisition was also amphibious with two
lines of instruments deployed onshore simultaneously with off-
shore lines. Onshore short-period data collection was further
bolstered by subsequent deployment of ∼800 instruments and
11 onshore shots. Four lines of SPOBSs and ∼4800 km of MCS
data were collected offshore. This unprecedented geophysical
dataset has already produced several studies than span scales
and geophysical data types (e.g., Greene et al., 2017;Lynner
and Bodmer, 2017;Lynner and Porritt, 2017;Hill et al., 2018)
and will continue to support a wide scope of scientific analyses,
ranging from the critical zone to Earth’s deep interior.
Data and Resources
The data discussed in this article were collected as part of the eastern
North American margin community seismic experiment (ENAM-CSE)
10–1 10 010110 2
Period (s)
–200
(a) (b)
–180
–160
–140
–120
–100
–80
–60
Power (dB)
–5.0
–4.5
–4.0
–3.5
–3.0
–2.5
–2.0
–1.5
OBS depth (km)
10
–1
10
0
10
1
Period (s)
–200
–180
–160
–140
–120
–100
–80
–60
Power (dB)
–5.0
–4.5
–4.0
–3.5
–3.0
–2.5
–2.0
–1.5
–1.0
–0.5
SPOBS depth (km)
6 Hz spike
Broadband OBS Short-period OBS
HNM
LNM
HNM
LNM
Figure 5. Mean noise spectra for the vertical components colored
by deployment depth for (a) broadband OBS and (b) SPOBS
instruments. Spectra for the three onshore broadband stations are
shown in red and high-noise (HNMs) and low-noise models (LNMs)
models in black. For both the broadband and SPOBS stations,
shallower-water stations generally exhibit higher noise levels than
deeper-water stations. An anomalous peak at ∼6Hzcanbeseen
in some of the SPOBS instruments. Problematic stations are not
plotted due to noisy or compromised data. The color version of this
figure is available only in the electronic edition.
538 Seismological Research Letters www.srl-online.org •Volume 91 •Number 1 •January 2020
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and are publically available. The short-period and broadband ocean-
bottom seismometer (OBS) data, along with data from the three coastal
Outer Banks stations, are archived at the Incorporated Research
Institutions for Seismology Data Management Center (IRIS-DMC)
under network code YO (Gaherty et al.,2014). The IRIS-DMC also
hosts the onshore short-period datasets under network ZI (Magnani
and Lizarralde, 2014;Magnani, Van Avendonk, et al., 2015) and the
EarthScope Transportable Array (TA) data under network TA (IRIS
Transportable Array, 2003). Metrics requested from Modular Utility
for STAtistical kNowledge Gathering (MUSTANG),the IRIS data qual-
ity metrics service, were used and can be accessed at service.iris.edu/
mustang. The multichannel seismic (MCS), bathymetry, gravity,
and magnetic data are available through the Marine Geoscience
Data System (MGDS) (Shillington et al.,2014a,b). The OBS seismic
refraction data are also available in SEGY format through the
Interdisciplinary Earth Data Alliance (IEDA) in the form of field data
with a cruise report (Van Avendonk et al., 2014), and processed,
relocated data (Van Avendonk et al.,2015). Cruise reports for the
R/V Endeavour and R/V Marcus G. Langseth can be found at
http://ds.iris.edu/data/reports/YO_2014_2015/.Reportfortheonshore
active-source deployment and shots can be found at http://ds.iris.
edu/data/reports/ZI_2014_2014/. The supplemental material for this
article includes a table of ENAM-CSE stations with known issues
and figures showing station drifts, percent data return, and station noise
characteristics.
Acknowledgments
The authors thank all of the volunteer participants, the ocean-bottom
seismometer (OBS) technicians from Woods Hole Oceanographic
Institution (WHOI) and Scripps Institution of Oceanography (SIO),
the crews of the R/V Marcus G. Langseth and R/V Endeavor, and all
those who contributed to the eastern North American margin com-
munity seismic experiment (ENAM-CSE) concept. The authors thank
many people, schools, companies, and state and local governmental
institutions that gave them permission to install seismic stations
onshore and undertake onshore seismic shooting. The OBS instru-
ments came from the U.S. Ocean Bottom Seismic Instrument Pool
(OBSIP). Onshore stations were provided by Incorporated Research
Institutions for Seismology–Program for the Array Seismic Studies of
the Continental Lithosphere (IRIS-PASSCAL) instrument center. Several
figures were made using Generic Mapping Tools (GMT; Wessel and
Smith, 1999). Data collection was supported by the National Science
Foundation (NSF) through the Geodynamic Processes at Rifting
and Subducting Margins (GeoPRISMS) program. This work and the
ENAM-CSE were funded by NSF Grant Numbers EAR-1753759,
EAR-1753722, OCE-1348454, OCE-1347498, OCE-1348124,
OCE-1348228, OCE-1348934, OCE-1348342, OCE-1347310, and
OCE-1347024. The authors thank three anonymous reviewers for useful
comments.
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Manuscript received 14 June 2019
Published online 30 October 2019
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