A Systematic Study of Earthquake Source Mechanism and Regional Stress Field in the Southern Montney Unconventional Play of Northeast British Columbia, Canada

2019 ◽  
Vol 91 (1) ◽  
pp. 195-206 ◽  
Author(s):  
Alireza Babaie Mahani ◽  
Fatemeh Esfahani ◽  
Honn Kao ◽  
Michelle Gaucher ◽  
Mark Hayes ◽  
...  
Keyword(s):  
British Columbia ◽  
Stress Field ◽  
Horizontal Stress ◽  
Strike Slip ◽  
P Wave ◽  
Source Mechanism ◽  
Induced Earthquakes ◽  
Nodal Plane ◽  
Reverse Faulting ◽  
Best Fitting

Abstract We provide a close look at the source mechanism of hydraulically fractured induced earthquakes and the in situ stress field within the southern Montney unconventional play in the northeast British Columbia, Canada. P‐wave first‐motion focal mechanisms were obtained for 66 earthquakes with magnitudes between 1.5 and 4.6. Results show that strike‐slip movement is the prevailing source mechanism for the events in this area, although reverse faulting is also observed for a few earthquakes. The best‐fitting nodal plane mostly strikes at ∼N60° E, with most events having dip angles of >60°. Using the Martinez‐Garzon et al. (2014) stress inversion module, we obtained the orientation of the three principal compressive stress (S1>S2>S3) and the relative intermediate principal stress magnitude (R) in five clusters. Assuming the best‐fitting nodal plane to be the causative fault, R values are mostly between 0.8 and 0.9 suggesting that the magnitude of S2 and S3 are similar, which is consistent with strike‐slip or reverse‐faulting regimes. The plunge of S1 varies between 1° and 3°, with its trend varying between N21°E and N34°E. On the other hand, the plunge of S3 varies between 22° and 50°, with its trend varies between N68°W and N58°W. Following Lund and Townend (2007), we calculated the trend of maximum horizontal stress to vary from N22°E to N33°E, in comparison with the average trend of N41°E from the World Stress Map (Heidbach et al., 2016). Through analysis of the Coulomb failure criterion and Mohr diagrams, we estimated the amount of pore‐pressure increase necessary to initiate shear slip to range between 4 and 29 MPa (average of 14±8  MPa) in the study area.

A New Uniform Moment Tensor Catalog for Yunnan, China, from January 2000 through December 2014

2020 ◽  
Vol 91 (2A) ◽  
pp. 891-900
Author(s):  
Yan Xu ◽  
Keith D. Koper ◽  
Relu Burlacu ◽  
Robert B. Herrmann ◽  
Dan-Ning Li
Keyword(s):  
Stress Field ◽  
Seismic Hazard ◽  
Moment Tensor ◽  
Horizontal Stress ◽  
Strike Slip ◽  
Moment Tensors ◽  
Yunnan Region ◽  
Seismic Waveforms ◽  
The Moment ◽  
Maximum Horizontal Stress

Abstract Because of the collision of the Indian and Eurasian tectonic plates, the Yunnan Province of southwestern China has some of the highest levels of seismic hazard in the world. In such a region, a catalog of moment tensors is important for estimating seismic hazard and helping understand the regional seismotectonics. Here, we present a new uniform catalog of moment tensor solutions for the Yunnan region. Using a grid-search technique to invert seismic waveforms recorded by the permanent regional network in Yunnan and the 2 yr ChinArray deployment, we present 1833 moment tensor solutions for small-to-moderate earthquakes that occurred between January 2000 and December 2014. Moment magnitudes in the new catalog vary from Mw 2.2 to 6.1, and the catalog is complete above Mw∼3.5–3.6. The moment tensors are constrained to be purely double-couple and show a variety of faulting mechanisms. Normal faulting events are mainly concentrated in northwest Yunnan, while farther south along the Sagaing fault the earthquakes are mostly thrust and strike slip. The remaining area includes all three styles of faulting but mostly strike slip. We invert the moment tensors for the regional stress field and find a strong correlation between spatially varying maximum horizontal stress and Global Positioning System observations of horizontal ground velocity. The stress field reveals clockwise rotation around the eastern Himalayan syntaxis, with northwest–southeast compression to the east of the Red River fault changing to northeast–southwest compression west of the fault. Almost 88% of the centroid depths are shallower than 16 km, consistent with a weak and ductile lower crust.

Focal mechanism and stress field in the northeastern Tibetan Plateau: insight into layered crustal deformations

2019 ◽  
Vol 218 (3) ◽  
pp. 2066-2078 ◽  
Author(s):  
Cunrui Han ◽  
Zhouchuan Huang ◽  
Mingjie Xu ◽  
Liangshu Wang ◽  
Ning Mi ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Stress Field ◽  
Focal Mechanism ◽  
Horizontal Stress ◽  
P Wave ◽  
The Tibetan Plateau ◽  
Linear Inversion ◽  
Focal Mechanism Solutions ◽  
Stress Orientations ◽  
Ne Tibetan Plateau

SUMMARY Focal mechanism solutions (FMSs) reflect the stress field underground directly. They provide essential clue for crustal deformations and therefore improve our understanding of tectonic uplift and expansion of the Tibetan Plateau. In this study, we applied generalized Cut and Paste and P-wave first-motion methods to determine 334 FMSs (2.0 ≤ Mw ≤ 6.4) with the data recorded by a new temporary network deployed in the NE Tibetan Plateau by ChinArray project. We then used 1015 FMSs (including 681 published FMSs) to calculate the regional stress field with a damped linear inversion. The results suggest dominant thrust and strike-slip faulting environments in the NE Tibetan Plateau. From the Qilian thrust belt to the Qinling orogen, the maximum horizontal stress orientations (${S_\mathrm{ H}}$) rotate clockwise from NNE to NE, and further to EW, showing a fan-shaped pattern. The derived minimum horizontal stress orientations (${S_\mathrm{ h}}$) are parallel to the aligned fabrics in the mantle lithosphere indicated by shear wave splitting measurements, suggesting vertically coherent deformation in the NE Tibetan Plateau. Beneath the SW Qinling adjacent to the plateau, however, the stress orientations in the shallow and deep crust are different, whereas the deep crustal stress field indicates possible ductile crustal flow or shear.

A seismological study of two Attica, New York earthquakes

1978 ◽  
Vol 68 (3) ◽  
pp. 641-651 ◽  
Author(s):  
Robert B. Herrmann
Keyword(s):  
New York ◽  
Source Parameters ◽  
Focal Depth ◽  
Strike Slip ◽  
Focal Mechanisms ◽  
The Other ◽  
Nodal Plane ◽  
Reverse Faulting ◽  
Epicentral Intensity ◽  
East West

abstract The Attica, New York earthquakes of January 1, 1966 and June 12, 1967 are studied in detail to obtain their focal mechanisms, depths and seismic moments. Both events have similar source parameters with one nodal plane striking about 120° and dipping 60°S and the other nodal plane striking about 20° and dipping 70°E. The fault motion on the NNE nodal plane has a component of right lateral strike slip and one of reverse faulting. Though this nodal plane parallels the Clarendon-Linden structure, the possibility of associating the other nodal plane with a diffuse east-west seismicity trend cannot be excluded. The shallow focal depth of 2 to 3 km for these two events can be used as an explanation of the relatively high epicentral intensity VIII of the Attica event of 1929.

THE STRESS FIELD OF THE NORTH WEST SHELF AND WELLBORE STABILITY

1993 ◽  
Vol 33 (1) ◽  
pp. 373 ◽  
Author(s):  
R.R. Millis ◽  
A.F. Williams
Keyword(s):  
Stress Field ◽  
Horizontal Stress ◽  
Strike Slip ◽  
Wellbore Stability ◽  
Upper And Lower Bounds ◽  
Theoretical Modelling ◽  
Elliptical Cross ◽  
North West ◽  
The North ◽  
Timor Sea

Boreholes drilled in the search for hydrocarbons in the Barrow-Dampier Sub-Basin (North West Shelf, Australia) commonly exhibit an elliptical cross-section believed to be due to stress-induced wellbore failure known as borehole breakout. The azimuths of the long axes of 138 discrete breakouts identified in nine different wells in the Barrow-Dampier show a consistent 010°−030°N trend implying that maximum horizontal compressive stress is oriented 100°−12G°N.The orientation of horizontal stress determined in this study (and that from the Timor Sea area which is rotated some 50°−60° with respect to the Barrow-Dampier) is consistent with that derived from theoretical modelling of the stress within the Indo-Australian plate based on the plate tectonic forces acting on its boundaries. The rotation of the horizontal stress orientations along the North West Shelf, between the Barrow-Dampier and the Timor Sea, is a reflection of the present-day complex plate convergence system at the north-eastern boundary of the Indo-Australian Plate.Vertical stress magnitudes, Sv, in the Barrow-Dampier were determined from density and sonic log data. Minimum and maximum horizontal stress magnitudes, Shmin and Shmax, were determined from mini-hydraulic fracture (or modified leak-off) test results. These data suggest that the fault condition of the Wanaea/Cossack area is on the boundary between normal faulting (extension) and strike-slip, i.e. Sv ≈ Shmax > Shmin. However, in other parts of the Barrow-Dampier the evidence suggests a strike-slip fault condition, i.e. Shmax > Sv > Shmin.Given the orientation of the stress field and the fault condition, inferences can be drawn regarding the stability of horizontal wells. Furthermore, experience from vertical wells can be utilized to determine the upper and lower bounds to the mud-weight envelope as functions of deviation and wellbore orientation. Since a horizontal well will see Sv and a horizontal stress, stress anisotropy around a wellbore in the Wanaea/Cossack area (and hence wellbore instability) will be minimized by drilling in the Shmin direction i.e. 010°–030°N.

scholarly journals Relocation and seismotectonic interpretation of the seismic swarm of August - December of 2012 in the Linares area, northeastern Mexico

2016 ◽  
Vol 55 (2) ◽  
Author(s):  
Carmen M. Gómez-Arredondo ◽  
Juan C. Montalvo-Arrieta ◽  
Arturo Iglesias-Mendoza ◽  
Victor H. Espíndola-Castro
Keyword(s):  
Fault Plane ◽  
Horizontal Stress ◽  
Nodal Plane ◽  
Fault Plane Solutions ◽  
Focal Mechanism Solutions ◽  
Reverse Faulting ◽  
Northeastern Mexico ◽  
Time Periods ◽  
Maximum Horizontal Stress ◽  
Seismotectonic Interpretation

We relocated 52 events of 2.5 ≤ Mc ≤ 3.6 from a seismic sequence of over 250 events that occurred during July-December 2012 southwest of the Linares area, northeastern Mexico. To examine this swarm four seismic stations were installed in the region and operated during different time periods from September to December. Relocation of the swarm showed that the earthquake hypocentral depths were at 8 (±5) km, and the time residuals had values ≤ 0.38 s. The fault plane solutions were generated for individual earthquakes and through the use of the composite mechanism technique. The focal mechanism solutions show pure reverse faulting; the SW dipping NNW - SSE trending nodal plane is the inferred fault plane (strike ~150°, dip ~50° and rake ~67°), which reveals that maximum horizontal stress (SHmax > Shmin > Sv) predominates in the area.

scholarly journals Crustal Strain and Stress Fields in Egypt from Geodetic and Seismological Data

2021 ◽  
Vol 13 (7) ◽  
pp. 1398
Author(s):  
Mohamed Rashwan ◽  
Rashad Sawires ◽  
Ali M. Radwan ◽  
Federica Sparacino ◽  
José Antonio Peláez ◽  
...  
Keyword(s):  
Stress Field ◽  
Large Scale ◽  
Nile Delta ◽  
Plate Boundary ◽  
Horizontal Stress ◽  
Strike Slip ◽  
Surface Strain ◽  
Gulf Of Aqaba ◽  
Seismological Data ◽  
Maximum Horizontal Stress

The comparison between crustal stress and surface strain azimuthal patterns has provided new insights into several complex tectonic settings worldwide. Here, we performed such a comparison for Egypt taking into account updated datasets of seismological and geodetic observations. In north-eastern Egypt, the stress field shows a fan-shaped azimuthal pattern with a WNW–ESE orientation on the Cairo region, which progressively rotated to NW–SE along the Gulf of Aqaba. The stress field shows a prevailing normal faulting regime, however, along the Sinai/Arabia plate boundary it coexists with a strike–slip faulting one (σ1 ≅ σ2 > σ3), while on the Gulf of Suez, it is characterized by crustal extension occurring on near-orthogonal directions (σ1 > σ2 ≅ σ3). On the Nile Delta, the maximum horizontal stress (SHmax) pattern shows scattered orientations, while on the Aswan region, it has a WNW–ESE strike with pure strike–slip features. The strain-rate field shows the largest values along the Red Sea and the Sinai/Arabia plate boundary. Crustal stretching (up to 40 nanostrain/yr) occurs on these areas with WSW–ENE and NE–SW orientations, while crustal contraction occurs on northern Nile Delta (10 nanostrain/yr) and offshore (~35 nanostrain/yr) with E–W and N–S orientations, respectively. The comparison between stress and strain orientations over the investigated area reveals that both patterns are near-parallel and driven by the same large-scale tectonic processes.

scholarly journals Driving stress and seismotectonic implications of the 2013 Mw5.8 Awaji Island earthquake, southwestern Japan, based on earthquake focal mechanisms before and after the mainshock

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Kazutoshi Imanishi ◽  
Makiko Ohtani ◽  
Takahiko Uchide
Keyword(s):  
Stress Field ◽  
Stress Tensor ◽  
Nankai Trough ◽  
Source Region ◽  
Local Scale ◽  
Southwest Japan ◽  
Stress Tensor Inversion ◽  
Earthquake Fault ◽  
Reverse Faulting ◽  
Before And After

Abstract A driving stress of the Mw5.8 reverse-faulting Awaji Island earthquake (2013), southwest Japan, was investigated using focal mechanism solutions of earthquakes before and after the mainshock. The seismic records from regional high-sensitivity seismic stations were used. Further, the stress tensor inversion method was applied to infer the stress fields in the source region. The results of the stress tensor inversion and the slip tendency analysis revealed that the stress field within the source region deviates from the surrounding area, in which the stress field locally contains a reverse-faulting component with ENE–WSW compression. This local fluctuation in the stress field is key to producing reverse-faulting earthquakes. The existing knowledge on regional-scale stress (tens to hundreds of km) cannot predict the occurrence of the Awaji Island earthquake, emphasizing the importance of estimating local-scale (< tens of km) stress information. It is possible that the local-scale stress heterogeneity has been formed by local tectonic movement, i.e., the formation of flexures in combination with recurring deep aseismic slips. The coseismic Coulomb stress change, induced by the disastrous 1995 Mw6.9 Kobe earthquake, increased along the fault plane of the Awaji Island earthquake; however, the postseismic stress change was negative. We concluded that the gradual stress build-up, due to the interseismic plate locking along the Nankai trough, overcame the postseismic stress reduction in a few years, pushing the Awaji Island earthquake fault over its failure threshold in 2013. The observation that the earthquake occurred in response to the interseismic plate locking has an important implication in terms of seismotectonics in southwest Japan, facilitating further research on the causal relationship between the inland earthquake activity and the Nankai trough earthquake. Furthermore, this study highlighted that the dataset before the mainshock may not have sufficient information to reflect the stress field in the source region due to the lack of earthquakes in that region. This is because the earthquake fault is generally locked prior to the mainshock. Further research is needed for estimating the stress field in the vicinity of an earthquake fault via seismicity before the mainshock alone.

scholarly journals S-wave experiments for the exploration of a deep geothermal carbonate reservoir in the German Molasse Basin

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Britta Wawerzinek ◽  
Hermann Buness ◽  
Hartwig von Hartmann ◽  
David C. Tanner
Keyword(s):  
Upper Jurassic ◽  
Carbonate Reservoir ◽  
P Wave ◽  
Seismic Survey ◽  
Seismic Exploration ◽  
Molasse Basin ◽  
S Wave ◽  
Induced Earthquakes ◽  
Conversion Point ◽  
Facies Classification

AbstractThere are many successful geothermal projects that exploit the Upper Jurassic aquifer at 2–3 km depth in the German Molasse Basin. However, up to now, only P-wave seismic exploration has been carried out. In an experiment in the Greater Munich area, we recorded S-waves that were generated by the conventional P-wave seismic survey, using 3C receivers. From this, we built a 3D volume of P- to S-converted (PS) waves using the asymptotic conversion point approach. By combining the P-volume and the resulting PS-seismic volume, we were able to derive the spatial distribution of the vp/vs ratio of both the Molasse overburden and the Upper Jurassic reservoir. We found that the vp/vs ratios for the Molasse units range from 2.0 to 2.3 with a median of 2.15, which is much higher than previously assumed. This raises the depth of hypocenters of induced earthquakes in surrounding geothermal wells. The vp/vs ratios found in the Upper Jurassic vary laterally between 1.5 and 2.2. Since no boreholes are available for verification, we test our results against an independently derived facies classification of the conventional 3D seismic volume and found it correlates well. Furthermore, we see that low vp/vs ratios correlate with high vp and vs velocities. We interpret the latter as dolomitized rocks, which are connected with enhanced permeability in the reservoir. We conclude that 3C registration of conventional P-wave surveys is worthwhile.

Fractures in the northern plains, stream patterns, and the midcontinent stress field

1987 ◽  
Vol 24 (6) ◽  
pp. 1086-1097 ◽  
Author(s):  
Mel R. Stauffer ◽  
Don J. Gendzwill
Keyword(s):  
Stress Field ◽  
Horizontal Stress ◽  
The Body ◽  
North American Plate ◽  
Plate Motion ◽  
Viscous Drag ◽  
Near Surface ◽  
The North ◽  
Elastic Rebound ◽  
Western North Dakota

Fractures in Late Cretaceous to Late Pleistocene sediments in Saskatchewan, eastern Montana, and western North Dakota form two vertical, orthogonal sets trending northeast–southwest and northwest–southeast. The pattern is consistent, regardless of rock type or age (except for concretionary sandstone). Both sets appear to be extensional in origin and are similar in character to joints in Alberta. Modem stream valleys also trend in the same two dominant directions and may be controlled by the underlying fractures.Elevation variations on the sub-Mannville (Early Cretaceous) unconformity form a rectilinear pattern also parallel to the fracture sets, suggesting that fracturing was initiated at least as early as Late Jurassic. It may have begun earlier, but there are insufficient data at present to extend the time of initiation.We interpret the fractures as the result of vertical uplift together with plate motion: the westward drift of North America. The northeast–southwest-directed maximum principal horizontal stress of the midcontinent stress field is generated by viscous drag effects between the North American plate and the mantle. Vertical uplift, erosion, or both together produce a horizontal tensile state in near-surface materials, and with the addition of a directed horizontal stress through plate motion, vertical tension cracks are generated parallel to that horizontal stress (northeast–southwest). Nearly instantaneous elastic rebound results in the production of second-order joints (northwest–southeast) perpendicular to the first. In this manner, the body of rock is being subjected with time to complex alternation of northeast–southwest and northwest–southeast horizontal stresses, resulting in the continuous and contemporaneous production of two perpendicular extensional joint sets.

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