Dense surface seismic data confirm non-double-couple source mechanisms induced by hydraulic fracturing

Geophysics ◽  
2016 ◽  
Vol 81 (6) ◽  
pp. KS207-KS217 ◽  
Author(s):  
Jeremy D. Pesicek ◽  
Konrad Cieślik ◽  
Marc-André Lambert ◽  
Pedro Carrillo ◽  
Brad Birkelo
Keyword(s):  
Hydraulic Fracturing ◽  
Seismic Data ◽  
P Wave ◽  
Source Modeling ◽  
Moment Tensors ◽  
Amplitude Data ◽  
Double Couple ◽  
Source Mechanisms ◽  
Source Models ◽  
Favorable Conditions

We have determined source mechanisms for nine high-quality microseismic events induced during hydraulic fracturing of the Montney Shale in Canada. Seismic data were recorded using a dense regularly spaced grid of sensors at the surface. The design and geometry of the survey are such that the recorded P-wave amplitudes essentially map the upper focal hemisphere, allowing the source mechanism to be interpreted directly from the data. Given the inherent difficulties of computing reliable moment tensors (MTs) from high-frequency microseismic data, the surface amplitude and polarity maps provide important additional confirmation of the source mechanisms. This is especially critical when interpreting non-shear source processes, which are notoriously susceptible to artifacts due to incomplete or inaccurate source modeling. We have found that most of the nine events contain significant non-double-couple (DC) components, as evident in the surface amplitude data and the resulting MT models. Furthermore, we found that source models that are constrained to be purely shear do not explain the data for most events. Thus, even though non-DC components of MTs can often be attributed to modeling artifacts, we argue that they are required by the data in some cases, and can be reliably computed and confidently interpreted under favorable conditions.

A teleseismic body-wave analysis of the May 1980 Mammoth Lakes, California, earthquakes

1983 ◽  
Vol 73 (2) ◽  
pp. 419-434
Author(s):  
Jeffery S. Barker ◽  
Charles A. Langston
Keyword(s):  
Body Wave ◽  
Moment Tensor ◽  
Normal Fault ◽  
Strike Slip ◽  
Body Waves ◽  
P Wave ◽  
Moment Tensors ◽  
Double Couple ◽  
The Moment ◽  
Mammoth Lakes

abstract Teleseismic P-wave first motions for the M ≧ 6 earthquakes near Mammoth Lakes, California, are inconsistent with the vertical strike-slip mechanisms determined from local and regional P-wave first motions. Combining these data sets allows three possible mechanisms: a north-striking, east-dipping strike-slip fault; a NE-striking oblique fault; and a NNW-striking normal fault. Inversion of long-period teleseismic P and SH waves for the events of 25 May 1980 (1633 UTC) and 27 May 1980 (1450 UTC) yields moment tensors with large non-double-couple components. The moment tensor for the first event may be decomposed into a major double couple with strike = 18°, dip = 61°, and rake = −15°, and a minor double couple with strike = 303°, dip = 43°, and rake = 224°. A similar decomposition for the last event yields strike = 25°, dip = 65°, rake = −6°, and strike = 312°, dip = 37°, and rake = 232°. Although the inversions were performed on only a few teleseismic body waves, the radiation patterns of the moment tensors are consistent with most of the P-wave first motion polarities at local, regional, and teleseismic distances. The stress axes inferred from the moment tensors are consistent with N65°E extension determined by geodetic measurements by Savage et al. (1981). Seismic moments computed from the moment tensors are 1.87 × 1025 dyne-cm for the 25 May 1980 (1633 UTC) event and 1.03 × 1025 dyne-cm for the 27 May 1980 (1450 UTC) event. The non-double-couple aspect of the moment tensors and the inability to obtain a convergent solution for the 25 May 1980 (1944 UTC) event may indicate that the assumptions of a point source and plane-layered structure implicit in the moment tensor inversion are not entirely valid for the Mammoth Lakes earthquakes.

Multidisciplinary Analysis of Hydraulic Stimulation and Production Effects within the Niobrara and Codell Reservoirs, Wattenberg Field, Colorado: Part 2 — Analysis of Hydraulic Fracturing and Production

2021 ◽  
pp. 1-53
Author(s):  
Matthew Bray ◽  
Jakob Utley ◽  
Yanrui Ning ◽  
Angela Dang ◽  
Jacquelyn Daves ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Seismic Data ◽  
Time Lapse ◽  
Production Performance ◽  
P Wave ◽  
Production Data ◽  
Total Production ◽  
Wattenberg Field ◽  
Reservoir Models ◽  
3D Geomechanical Model

Enhanced hydrocarbon recovery is essential for continued economic development of unconventional reservoirs. Our study focuses on dynamic characterization of the Niobrara and Codell Formations in Wattenberg Field through the development and analysis of a full integrated reservoir model. We demonstrate the effectiveness of hydraulic fracturing and production with two seismic monitor surveys, surface microseismic, completion data, and production data. The two monitor surveys were recorded after stimulation, and again after two years of production. Identification of reservoir deformation due to hydraulic fracturing and production improves reservoir models by mapping non-stimulated and non-producing zones. Monitoring these time-variant changes improves the prediction capability of reservoir models, which in turn leads to improved well and stage placement. We quantify dynamic reservoir changes with time-lapse P-wave seismic data utilizing pre-stack inversion, and velocity-independent layer stripping for velocity and attenuation changes within the Niobrara and Codell reservoirs. A 3D geomechanical model and production data are history matched, and a simulation is run for two years of production. Results are integrated with time-lapse seismic data to illustrate the effects of hydraulic fracturing and production. Our analyses illustrate that chalk facies have significantly higher hydraulic fracture efficiency and production performance than marl facies. Additionally, structural and hydraulic complexity associated with faults generate spatial variability in a well’s total production.

Analysis of non-double-couple source mechanisms in an area of induced seismicity, West Texas (USA).

2021 ◽  
Author(s):  
Savvaidis Alexandros ◽  
Roselli Pamela
Keyword(s):  
Stress Field ◽  
Time Domain ◽  
Seismic Moment ◽  
Moment Tensor ◽  
P Wave ◽  
Seismic Moment Tensor ◽  
Ground Displacement ◽  
Moment Tensors ◽  
West Texas ◽  
Double Couple

<p>In the scope to investigate the possible interactions between injected fluids, subsurface geology, stress field and triggering earthquakes, we investigate seismic source parameters related to the seismicity in West Texas (USA). The analysis of seismic moment tensor is an excellent tool to understand earthquake source process kinematics; moreover, changes in the fluid volume during faulting leads to existence of non-double-couple (NDC) components (Frohlich, 1994; Julian et al., 1998; Miller et al., 1998). The NDC percentage in the source constitutes the sum of absolute ISO and CLVD components so that %NDC= % ISO + %CLVD and %ISO+%CLVD+%DC=100%. It is currently known that the presence of NDC implies more complex sources (mixed shear-tensile earthquakes) correlated to fluid injections, geothermal systems and volcano-seismology where induced and triggered seismicity is observed.</p><p>With this hypothesis, we analyze the micro-earthquakes (M <2 .7) recorded by the Texas Seismological Network (TexNet) and a temporary network constituted by 40 seismic stations (equipped by either broadband or 3 component geophones). Our study area is characterized by Northwest-Southeast faults that follow the local stress/field (SH<sub>max</sub>) and the geological characteristic of the shallow basin structure of the study area. After a selection based on signal-to-noise ratio, we filter (1-50 Hz) the seismograms and estimate P-wave pulse polarities and the first P-wave ground displacement pulse in time domain. Then, we perform the full moment tensor analysis by using hybridMT technique (Andersen, 2001; Kwiatek et al., 2016) with a detailed 1D velocity model. The key parameter is the polarity/area of the first P-wave ground displacement pulse in time domain. Uncertainties of estimated moment tensors are expressed by normalized root-mean-square (RMS errors) between theoretical and estimated amplitudes (Vavricuk et al., 2014). We also evaluate the quality of the seismic moment tensors by bootstrap and resampling. In our preliminary results we obtain NDC percentage (in terms of %ISO and %CLVD components), Mw, seismic moment, P, T and B axes orientation for each source inverted.</p>

Seismological Constraints on Fault-Slip Source Models and Rupture Characteristics of Global Large Earthquakes (Mw ≥ 7.5) and Associated Tsunamis

2020 ◽  
Author(s):  
Seda Yolsal-Çevikbilen ◽  
Tuncay Taymaz
Keyword(s):  
Near Field ◽  
Fault Slip ◽  
Earthquake Source ◽  
P Wave ◽  
Slip Distribution ◽  
Distribution Models ◽  
Tsunami Waves ◽  
Source Mechanisms ◽  
Source Models ◽  
Large Earthquakes

<p>Large and destructive earthquakes (M<sub>w</sub>≥ 7.5) occur worldwide particularly along the major subduction zones causing extensive damage and loss of life in the hinterland of epicentral region. Source models and rupture characteristics of these earthquakes (i.e. faulting geometry, focal depth, non-uniform finite-fault slip distributions) can be precisely determined by using seismological data and multidisciplinary earth-science observations. It is also known that earthquake source parameters play key roles in the modelling of secondary events such as earthquake-induced tsunamis. There are many studies emphasizing the importance of using heterogonous slip distribution models of earthquakes in mathematical tsunami simulations to predict synthetic tsunami waves more consistent with the observed ones. In this study, we obtained double-couple source mechanisms and slip distribution models of complex large earthquakes (M<sub>w</sub>≥ 7.5) lately occurred at different parts of the Earth. For this purpose, we used point-source teleseismic P- and SH- body waveform inversion and kinematic slip distribution inversion techniques. Besides, azimuthal distributions of P- wave first motion polarities, which are recorded by near-field and regional seismic stations, are checked to approve obtained minimum misfit source mechanism parameters of earthquakes. We essentially observed that tsunamigenic earthquakes occurred at shallow focal depths (h ≤ 70 km) with dip-slip source mechanisms and rather complex slip distributions along the fault planes. However, in some cases, tsunami waves may be unexpectedly triggered due to the secondary effects of large strike-slip earthquakes (e.g., September 28, 2018 Palu, Indonesia - M<sub>w</sub>7.5). Here, we discuss our inversion results, which reveal the significant contributions of earthquake source studies on resolving the relationships between the faulting geometry, rupture characteristics and tsunami generation. Furthermore, the necessity of high-resolution bathymetry data in numerical tsunami simulations is highlighted for the modelling of tsunami waves, in particular, recorded at the near-field tide-gauge stations. This study is partially supported by the Turkish Academy of Sciences (TÜBA) through GEBIP program.</p>

Source processes of industrially‐induced earthquakes at The Geysers geothermal area, California

Geophysics ◽  
1999 ◽  
Vol 64 (6) ◽  
pp. 1877-1889 ◽  
Author(s):  
Alwyn Ross ◽  
G. R. Foulger ◽  
Bruce R. Julian
Keyword(s):  
Geothermal Area ◽  
S Wave ◽  
Induced Earthquakes ◽  
Stress Regime ◽  
Moment Tensors ◽  
Text Structures ◽  
Double Couple ◽  
Source Mechanisms ◽  
The Geysers ◽  
Steam Production

Microearthquake activity at The Geysers geothermal area, California, mirrors the steam production rate, suggesting that the earthquakes are industrially induced. A 15-station network of digital, three‐component seismic stations was operated for one month in 1991, and 3,900 earthquakes were recorded. Highly‐accurate moment tensors were derived for 30 of the best recorded earthquakes by tracing rays through tomographically derived 3-D [Formula: see text] and [Formula: see text] structures, and inverting P- and S-wave polarities and amplitude ratios. The orientations of the P- and T-axes are very scattered, suggesting that there is no strong, systematic deviatoric stress field in the reservoir, which could explain why the earthquakes are not large. Most of the events had significant non‐double‐couple (non-DC) components in their source mechanisms with volumetric components up to ∼30% of the total moment. Explosive and implosive sources were observed in approximately equal numbers, and must be caused by cavity creation (or expansion) and collapse. It is likely that there is a causal relationship between these processes and fluid reinjection and steam withdrawal. Compensated linear vector dipole (CLVD) components were up to 100% of the deviatoric component. Combinations of opening cracks and shear faults cannot explain all the observations, and rapid fluid flow may also be involved. The pattern of non-DC failure at The Geysers contrasts with that of the Hengill‐Grensdalur area in Iceland, a largely unexploited water‐dominated field in an extensional stress regime. These differences are poorly understood but may be linked to the contrasting regional stress regimes and the industrial exploitation at The Geysers.

Uncertainties in Seismic Moment Tensors Inferred from Differences between Global Catalogs

2021 ◽  
Author(s):  
Boris Rösler ◽  
Seth Stein ◽  
Bruce D. Spencer
Keyword(s):  
Moment Tensor ◽  
Centroid Moment Tensor ◽  
Moment Tensors ◽  
Double Couple ◽  
Source Mechanisms ◽  
Order Of Magnitude ◽  
The Difference ◽  
The Moment ◽  
Source Geometry ◽  
Scalar Moment

Abstract Catalogs of moment tensors form the foundation for a wide variety of seismological studies. However, assessing uncertainties in the moment tensors and the quantities derived from them is difficult. To gain insight, we compare 5000 moment tensors in the U.S. Geological Survey (USGS) and the Global Centroid Moment Tensor (Global CMT) Project catalogs for November 2015–December 2020 and use the differences to illustrate the uncertainties. The differences are typically an order of magnitude larger than the reported errors, suggesting that the errors substantially underestimate the uncertainty. The catalogs are generally consistent, with intriguing differences. Global CMT generally reports larger scalar moments than USGS, with the difference decreasing with magnitude. This difference is larger than and of the opposite sign from what is expected due to the different definitions of the scalar moment. Instead, the differences are intrinsic to the tensors, presumably in part due to different phases used in the inversions. The differences in double-couple components of source mechanisms and the fault angles derived from them decrease with magnitude. Non-double-couple (NDC) components decrease somewhat with magnitude. These components are moderately correlated between catalogs, with correlations stronger for larger earthquakes. Hence, small earthquakes often show large NDC components, but many have large uncertainties and are likely to be artifacts of the inversion. Conversely, larger earthquakes are less likely to have large NDC components, but these components are typically robust between catalogs. If so, these can indicate either true deviation from a double couple or source complexity. The differences between catalogs in scalar moment, source geometry, or NDC fraction of individual earthquakes are essentially uncorrelated, suggesting that the differences reflect the inversion rather than the source process. Despite the differences in moment tensors, the location and depth of the centroids are consistent between catalogs. Our results apply to earthquakes after 2012, before which many moment tensors were common to both catalogs.

A microearthquake swarm in 1965 near Mould Bay, N.W.T., Canada

1968 ◽  
Vol 58 (6) ◽  
pp. 1991-2011
Author(s):  
T. E. T. Smith ◽  
K. Whitham ◽  
W. T. Piché
Keyword(s):  
Particle Motion ◽  
Upper Mantle ◽  
P Wave ◽  
Tectonic Activity ◽  
Transverse Waves ◽  
Amplitude Data ◽  
P Wave Velocity ◽  
Double Couple ◽  
Epicentral Region ◽  
Frequency Magnitude

ABSTRACT In a 30-day period beginning March 29, 1965, some 2026 microearthquakes were recorded at MBC and by the array NPNT. About 10 per cent of them were located. The extent of the epicentral region was 3 sq km and of the hypocentral region 8 cu km. The centroid of the hypocenters was 12.6 km from MBC on an azimuth of 121° and at a depth of 6.8 km, very nearly on the strike of an old fault. Although no foreshock-aftershock series could be distinguished, the events were not independent nor randomly distributed in time. Particle motion diagrams were drawn for 10 events. These identified the longitudinal and transverse waves and confirmed the azimuths and angles of emergence obtained from amplitude data. The array data also confirmed the azimuths and yielded a P-wave velocity of 4.33 km/s near the surface. The magnitudes ranged from − 1.1 to 2.9 and the frequency-magnitude relation was: log N = 2.46 ( ± 0.01 ) − 0.68 ( ± 0.01 ) M L . The coefficient 0.68 suggests tectonic activity. The partition of energy between P and S, and the observed directions of motion (all compressions at MBC) are compatible with the double couple model of focal mechanism and motion on the old fault. However, magma movement cannot be entirely ruled out as there exists geomagnetic evidence of abnormally high upper mantle temperatures. The following energy-magnitude relation was determined from 100 events in the range 0.1 ≦ ML ≦ 1.6: log E = 10.1 ( ± 0.3 ) + 1.91 ( ± 0.03 ) M L .

Inversion for Shear-Tensile Focal Mechanisms Using an Unsupervised Physics-Guided Neural Network

2021 ◽  
Author(s):  
Hongliang Zhang ◽  
Kristopher A. Innanen ◽  
David W. Eaton
Keyword(s):  
Neural Network ◽  
Mean Squared Error ◽  
Search Algorithm ◽  
Focal Mechanisms ◽  
Training Data ◽  
P Wave ◽  
Neural Network Approach ◽  
Fracture Simulation ◽  
Amplitude Data ◽  
Source Mechanisms

Abstract We present a novel physics-guided neural network to estimate shear-tensile focal mechanisms for microearthquakes using displacement amplitudes of direct P waves. Compared with conventional data-driven fully connected (FC) neural networks, our physics-guided neural network is implemented in an unsupervised fashion and avoids the use of training data, which may be incomplete or unavailable. We incorporate three FC layers and a scaling and shifting layer to estimate shear-tensile focal mechanisms for multiple events. Then, a forward-modeling layer, which generates synthetic amplitude data based on the source mechanisms emerging from the previous layer, is added. The neural network weights are iteratively updated to minimize the mean squared error between observed and modeled normalized P-wave amplitudes. We apply this machine-learning approach to a set of 530 induced events recorded during hydraulic-fracture simulation of Duvernay Shale west of Fox Creek, Alberta, yielding results that are consistent with previously reported source mechanisms for the same dataset. A distinct cluster characterized by more complex mechanisms exhibits relatively large Kagan angles (5°–25°) compared with the previously reported best double-couple solutions, mainly due to model simplification of the shear-tensile focal mechanism. Uncertainty tests demonstrate the robustness of the inversion results and high tolerance of our neural network to errors in event locations, the velocity model, and P-wave amplitudes. Compared with a single-event grid-search algorithm to estimate shear-tensile focal mechanisms, the proposed neural network approach exhibits significantly higher computational efficiency.

Multidisciplinary Analysis of Hydraulic Stimulation and Production Effects within the Niobrara and Codell Reservoirs, Wattenberg Field, Colorado: Part 1 - Baseline Reservoir Conditions

2021 ◽  
pp. 1-41
Author(s):  
Matthew Bray ◽  
Jacquelyn Daves ◽  
Daniel Brugioni ◽  
Asm Kamruzzaman ◽  
Tom Bratton ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Seismic Data ◽  
Time Lapse ◽  
Organic Content ◽  
P Wave ◽  
Seismic Survey ◽  
Fracture Density ◽  
Niobrara Formation ◽  
Reservoir Properties ◽  
Wattenberg Field

In the Wattenberg Field, the Reservoir Characterization Project at the Colorado School of Mines and Occidental Petroleum Corporation (Oxy) (formerly the Anadarko Petroleum Corporation) collected time-lapse seismic data for characterization of changes in the reservoir caused by hydraulic fracturing and production in the Niobrara Formation and Codell Sandstone member of the Carlile Formation. We have acquired three multicomponent seismic surveys to understand the dynamic reservoir changes caused by hydraulic fracturing and production of 11 horizontal wells within a 1 mi2 section (the Wishbone Section). The time-lapse seismic survey acquisition occurred immediately after the wells were drilled, another survey after stimulation, and a third survey after two years of production. In addition, we integrate core, petrophysical properties, fault and fracture characteristics, as well as P-wave seismic data to illustrate reservoir properties prior to simulation and production. Core analysis indicates extensive amounts of bioturbation in zones of high total organic content (TOC). Petrophysical analysis of logs and core samples indicates that chalk intervals have high amounts of TOC (>2%) and the lowest amount of clay in the reservoir interval. Core petrophysical characterization included X-ray diffraction analysis, mercury intrusion capillary pressure, N2 gas adsorption, and field emission scanning electron microscopy. Reservoir fractures follow four regional orientations, and chalk facies contain higher fracture density than marl facies. Integration of these data assist in enhanced well targeting and reservoir simulation.

Attribute-assisted footprint suppression using a 2D continuous wavelet transform

2018 ◽  
Vol 6 (2) ◽  
pp. T457-T470 ◽  
Author(s):  
Abdulmohsen Alali ◽  
Gabriel Machado ◽  
Kurt J. Marfurt
Keyword(s):  
Wavelet Transform ◽  
Continuous Wavelet Transform ◽  
Seismic Data ◽  
Wave Impedance ◽  
P Wave ◽  
Continuous Wavelet ◽  
Seismic Attribute ◽  
Attribute Data ◽  
Amplitude Data ◽  
Seismic Acquisition

Acquisition footprint manifests itself on 3D seismic data as a repetitive pattern of noise, anomalously high amplitudes, or structural shifts on time or horizon slices that is correlated to the location of the sources and receivers on the earth’s surface. Ideally, footprint suppression should be handled by denser seismic acquisition and more careful prestack processing prior to seismic imaging. In the case in which only legacy data exist, or when economic and time constraints preclude more expensive acquisition and more careful processing, interpreters must deal with data contaminated by footprint. Although accurate time-structure maps can be constructed from footprint-contaminated data, the effect of footprint on subsequent attributes, such as coherence, curvature, spectral components, and P-wave impedance will be exacerbated. We have developed a workflow that uses a 2D continuous wavelet transform to suppress coherent and incoherent noise on poststack seismic data. The method involves decomposing time slices of amplitude and attribute data into voices and magnitudes using 2D wavelets. We exploit the increased seismic attribute sensitivity to the acquisition footprint to design a mask to suppress the footprint on the original amplitude data. The workflow is easy to apply and improves the interpretability of the data and improves the subsequent attribute resolution.

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