The LArge‐n Seismic Survey in Oklahoma (LASSO) Experiment

2019 ◽  
Author(s):  
Sara L. Dougherty ◽  
Elizabeth S. Cochran ◽  
Rebecca M. Harrington
Keyword(s):  
Vertical Component ◽  
Seismic Survey ◽  
Spatiotemporal Evolution ◽  
Wastewater Disposal ◽  
Event Sequences ◽  
Large N ◽  
Field Deployment ◽  
Stress Drops ◽  
Seismic Wavefield ◽  
Induced Seismic Activity

ABSTRACT In 2016, the U.S. Geological Survey deployed >1800 vertical-component nodal seismometers in Grant County, Oklahoma, to study induced seismic activity associated with production of the Mississippi limestone play. The LArge‐n Seismic Survey in Oklahoma (LASSO) array operated for approximately one month, covering a 25 km by 32 km region with a nominal station spacing of ∼400  m. Primary goals of the deployment were to detect microseismic events not captured by the sparser regional network stations and to provide nearly unaliased records of the seismic wavefield. A more complete record of earthquakes allows us to map the spatiotemporal evolution of induced event sequences and illuminates the structures on which the events occur. Dense records of the seismic wavefield also provide improved measurements of the earthquake source, including focal mechanisms and stress drops. Taken together, we can use these findings to glean insights into the processes that induce earthquakes. Here, we describe the array layout, features of the nodal sensors, data recording configurations, and the field deployment. We also provide examples of earthquake waveforms recorded by the array to illustrate data quality and initial observations. LASSO array data provide a significant resource for understanding the occurrence of earthquakes induced by wastewater disposal.

Exploring the Evolution and Source Properties of Injection-Induced Seismicity in Northern Oklahoma Using a Large-N Seismic Array

2020 ◽  
Author(s):  
Kilian B. Kemna ◽  
Alexander Wickham-Piotrowski ◽  
Andrés F. Peña-Castro ◽  
Elizabeth S. Cochran ◽  
Rebecca M. Harrington
Keyword(s):  
Radiation Pattern ◽  
Stress Drop ◽  
Induced Seismicity ◽  
Frequency Estimation ◽  
Vertical Component ◽  
Spectral Ratio ◽  
Focal Mechanisms ◽  
Seismic Survey ◽  
Corner Frequency ◽  
Large N

<p>The LArge-n Seismic Survey in Oklahoma (LASSO) array recorded local seismicity in 2016 in a region of active saltwater disposal. The month-long deployment of 1,833 vertical-component nodes had a nominal station spacing of 400 m and covered a 25 by 32 km<sup>2</sup> area. We estimate local event magnitudes and focal mechanisms of the induced seismicity using the vertical component waveforms from a catalog of 1375 earthquakes. Here we use the developed catalog to investigate the spatio-temporal evolution of seismicity and the source properties of the induced events.</p><p>The catalog is complete to a local magnitude of ~0.9, with a b-value of ~1.1. Focal mechanisms, which we determined using the HASH method, show a mix of strike-slip and normal faulting. The majority of the events are located at 1.5 – 5.0 km depth, where injection depths range from 0.1 – 2.0 km, and the basement contact is located at 1.5 – 2.5 km. Analysis of the coefficient of variation of interevent times suggests that the time evolution of seismicity is close to Poissonian, with minimal temporal clustering. We observe spatial clustering, with larger (M > 2) events occurring within dense clusters near the footprint of the array.</p><p>The dense station coverage of the array permits the exploration of variations in corner frequency and resulting stress drop estimates as a function of azimuth, i.e. radiation pattern. We calculate stress drops for the local catalog within 5 km of the array footprint from individual spectral and spectral ratio corner frequency values. Single spectra corner frequency estimates for events within the array footprint on individual nodes show evidence of variation related to radiation pattern, and vary as much as 100% from the mean for an individual event. Stress drop estimates from spectral ratio corner frequency estimations range between 10 – 100 MPa, show self-similar scaling, and fall within the typical range observed for intraplate (tectonic) earthquakes. Both single spectra and spectral ratio corner frequency estimates show a significant sample bias in the corner frequency estimation by using less than ~10 stations, and highlight the importance of azimuthal coverage for the stability of spectral estimates.</p>

scholarly journals Azimuthally Dependent Seismic‐Wave Coherence at the Source Physics Experiment Large‐N Array

2019 ◽  
Vol 109 (5) ◽  
pp. 1935-1947
Author(s):  
Andréa Darrh ◽  
Christian Poppeliers ◽  
Leiph Preston
Keyword(s):  
Seismic Wave ◽  
Vertical Component ◽  
Linear Arrays ◽  
Seismic Scattering ◽  
Large N ◽  
2D Arrays ◽  
Physics Experiment ◽  
Seismic Wavefield ◽  
Source Physics ◽  
Chemical Explosion

Abstract We document azimuthally dependent seismic scattering at the Source Physics Experiment (SPE) using the large‐N array. The large‐N array recorded the seismic wavefield produced by the SPE‐5 buried chemical explosion, which occurred in April 2016 at the Nevada National Security Site, U.S.A. By selecting a subset of vertical‐component geophones from the large‐N array, we formed 10 linear arrays, with different nominal source–receiver azimuths as well as six 2D arrays. For each linear array, we evaluate wavefield coherency as a function of frequency and interstation distance. For both the P arrival and post‐P arrivals, the coherency is higher in the northeast propagation direction, which is consistent with the strike of the steeply dipping Boundary fault adjacent to the northwest side of the large‐N array. Conventional array analysis using a suite of 2D arrays suggests that the presence of the fault may help explain the azimuthal dependence of the seismic‐wave coherency for all wave types. This fault, which separates granite from alluvium, may be acting as a vertically oriented refractor and/or waveguide.

The corner frequencies and stress drops of intraplate earthquakes in the northeastern United States

1998 ◽  
Vol 88 (2) ◽  
pp. 531-542 ◽  
Author(s):  
Jinghua Shi ◽  
Won-Young Kim ◽  
Paul G. Richards
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Vertical Component ◽  
Corner Frequency ◽  
Northeastern United States ◽  
Empirical Green’S Function ◽  
Intraplate Earthquakes ◽  
Short Period ◽  
Empirical Green's Function ◽  
Stress Drops

Abstract This article presents the estimation of stress drops for small to middle-sized intraplate earthquakes in the northeastern United States. The vertical-component Sg and Lg waves of 49 earthquakes were analyzed, and their seismic corner frequencies and seismic moments were determined. For these events, both short-period and broadband records were obtained from stations in the region. There are eight events each of which has an aftershock good enough to be treated as its empirical Green's function, and their corner frequencies were estimated from empirical Green's function methods. For the other events, the corner frequencies were directly estimated by the spectral fitting of the vertical component of the Sg- or Lg-wave displacement spectrum with the ω-square source spectral model, using the available broadband and high-frequency short-period data and a frequency-dependent Q correction. The static stress drops, Δσ, were then calculated from the corner frequency and seismic moment. From our study, the source corner frequencies estimated by fitting the Lg displacement spectrum with the assumed ω-square source model are more consistent with the corner frequencies measured from empirical Green's function deconvolution method than those estimated from the intersection of horizontal low-frequency spectral asymptote and a line indicating the ω−2 decay above the corner frequency. The source corner frequencies we estimated proved to be most appropriate for the small to middle-sized earthquakes. The static stress drops calculated from these corner-frequency estimates tend to be independent of seismic moment for events above a certain size. For earthquakes with size less than about 2 × 1020 dyne-cm, the stress drop tends to decrease with decreasing moment, suggesting a breakdown in self-similarity below a threshold magnitude. A characteristic rupture size of about 100 m is implied for these smaller earthquakes.

Comparing P-P, P-SV, and SV-P mode waves in the Midland Basin, West Texas

2016 ◽  
Vol 4 (2) ◽  
pp. T183-T190 ◽  
Author(s):  
Michael V. De Angelo ◽  
Bob A. Hardage
Keyword(s):  
Vertical Component ◽  
P Wave ◽  
Seismic Survey ◽  
Vertical Force ◽  
S Wave ◽  
Converted Wave ◽  
Midland Basin ◽  
West Texas ◽  
Exploration Risk ◽  
Seismic Acquisition

We acquired 3D multicomponent data in Andrews County, Midland Basin, West Texas with a seismic survey. We extracted direct-SV modes generated by a vertical-force source (an array of three inline vertical vibrators) from the vertical component of multicomponent geophones. This seismic mode, SV-P, was created by reprocessing legacy 2D/3D P-wave seismic data to create converted-wave data and consequently forgoing the need for a multicomponent seismic acquisition program to obtain important S-wave information from the subsurface. We have compared P-P, P-SV, and SV-P traveltime and amplitude characteristics to determine which seismic mode provided better characterization of the targeted reservoirs and reduced exploration risk.

Minimal Clustering of Injection-Induced Earthquakes Observed with a Large-n Seismic Array

2020 ◽  
Vol 110 (5) ◽  
pp. 2005-2017 ◽  
Author(s):  
Elizabeth S. Cochran ◽  
Alexander Wickham-Piotrowski ◽  
Kilian B. Kemna ◽  
Rebecca M. Harrington ◽  
Sara L. Dougherty ◽  
...  
Keyword(s):  
Nearest Neighbor ◽  
Seismic Array ◽  
Seismic Survey ◽  
Single Event ◽  
Induced Earthquakes ◽  
Injection Wells ◽  
Independent Events ◽  
Large N ◽  
Aftershock Sequences ◽  
Stress Changes

ABSTRACT The clustering behavior of injection-induced earthquakes is examined using one month of data recorded by the LArge-n Seismic Survey in Oklahoma (LASSO) array. The 1829-node seismic array was deployed in a 25  km×32  km area of active saltwater disposal in northern Oklahoma between 14 April and 10 May 2016. Injection rates in the study area are nearly constant around the time of the deployment. We develop a local magnitude (ML) equation for the region and estimate magnitudes for 1104 earthquakes recorded by the deployment. The determined earthquake magnitudes range from ML 0.01 to 3.0. The majority of earthquakes occurred between 1.5 and 5.5 km depth, and the shallowest earthquake depths overlap with the base of injection wells at depths between 1.5 and 2.5 km. We compute focal mechanisms of the largest events (ML>2.0), and find a mix of normal- and strike-slip-faulting types. Earthquakes occur regularly in time during the deployment, but are not evenly distributed in space across the study area, that is, they are spatially clustered. Analysis of the nearest-neighbor distances in the space–time–magnitude domain shows the seismicity is dominated by single-event clusters (i.e., independent events). This high proportion of single-event clusters compared with multievent clusters has been previously noted for induced events at geothermal sites. When clustering occurs, the number of events in a cluster is typically small. We observe only four clusters with 10 or more events. For these larger clusters, we find equivalent numbers of foreshocks and aftershocks; however, the foreshock sequences are significantly longer in duration lasting days to tens of days, while aftershock sequences are observed only on the order of one day. The minimal clustering observed for events in the LASSO array suggests that the majority of events are being directly driven by stress changes due to local saltwater disposal.

Vertical hydrophone cable acquisition and imaging on land

Geophysics ◽  
2001 ◽  
Vol 66 (4) ◽  
pp. 1190-1194 ◽  
Author(s):  
J. S. Gulati ◽  
R. R. Stewart ◽  
B. H. Hoffe
Keyword(s):  
Seismic Data ◽  
Vertical Component ◽  
Oil Field ◽  
Seismic Survey ◽  
Predictive Deconvolution ◽  
Seismic Image ◽  
Seismic Sections

We acquired seismic data using a vertical hydrophone cable in a shallow, fluid‐filled borehole over the Blackfoot oil field in Alberta, Canada. The hydrophone data were recorded simultaneously with a surface seismic survey using dynamite sources. In addition, buried three‐component (3‐C) geophone data were acquired near the vertical cable. We observe that events on the hydrophone records are in phase with corresponding geophone data. Tube waves, which can be a problem on hydrophone data, are suppressed using a predictive deconvolution operator. Imaging, using the hydrophone data, results in a section that correlates well with a surface seismic image from vertical‐component geophone data. An anomaly, interpreted to be associated with the sand reservoir in the area, is evident on the hydrophone image (as well as on the surface seismic sections). The vertical hydrophone cable promises excellent imaging potential for land applications.

3D seismic imaging of volcanogenic massive sulfide deposits in the Flin Flon mining camp, Canada: Part 1 — Seismic results

Geophysics ◽  
2012 ◽  
Vol 77 (5) ◽  
pp. WC47-WC58 ◽  
Author(s):  
D. J. White ◽  
D. Secord ◽  
M. Malinowski
Keyword(s):  
Cross Sections ◽  
Vertical Component ◽  
Massive Sulfide ◽  
Seismic Survey ◽  
3D Seismic ◽  
Time Migration ◽  
3D Data ◽  
Strong Reflection ◽  
Flin Flon ◽  
Ore Zones

A [Formula: see text] 3D-3C seismic survey was conducted within the active Flin Flon mining camp located in Manitoba, Canada. The results for the vertical component data as obtained by conventional dip-moveout and prestack time-migration processing sequences and comparison of images from the 3D seismic volume with the subsurface location of known ore zones and the mine horizon generally showed a very good correlation. A well-defined diffraction response from the shallowest ore zone was observed in the unmigrated data with a corresponding phase reversal in the migrated data at the transition from intact ore to backfilled ore zone. The geometry of unmined and backfilled ore zones compared well with strong reflection amplitudes on corresponding cross sections to depths of [Formula: see text]. At greater depths, the ore zone had a weaker seismic signature due to a combination of effects, including imaging conditions, ore composition, and the increased presence of rhyolite within the mine horizon. In the case of the deeper ore zones that were characterized by low signal-to-noise levels, poststack migration was important in focusing weak ore-related reflections. The 3D data demonstrated the feasibility of detecting and accurately locating ore zones as small as a few million tons to depths of up to 1500 m.

Shale, Quakes, and High Stakes: Regulating Fracking-Induced Seismicity in Oklahoma, USA and Lancashire, UK

2019 ◽  
Vol 3 (1) ◽  
pp. 1-14
Author(s):  
Miriam R. Aczel ◽  
Karen E. Makuch
Keyword(s):  
United States ◽  
Hydraulic Fracturing ◽  
Shale Gas ◽  
Seismic Activity ◽  
Oil And Gas ◽  
Oil And Gas Industry ◽  
High Volume ◽  
The United States ◽  
Horizontal Drilling ◽  
Induced Seismic Activity

High-volume hydraulic fracturing combined with horizontal drilling has “revolutionized” the United States’ oil and gas industry by allowing extraction of previously inaccessible oil and gas trapped in shale rock [1]. Although the United States has extracted shale gas in different states for several decades, the United Kingdom is in the early stages of developing its domestic shale gas resources, in the hopes of replicating the United States’ commercial success with the technologies [2, 3]. However, the extraction of shale gas using hydraulic fracturing and horizontal drilling poses potential risks to the environment and natural resources, human health, and communities and local livelihoods. Risks include contamination of water resources, air pollution, and induced seismic activity near shale gas operation sites. This paper examines the regulation of potential induced seismic activity in Oklahoma, USA, and Lancashire, UK, and concludes with recommendations for strengthening these protections.

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