scholarly journals Size and orientation of the fault plane for the 2001 Gujarat, India earthquake (Mw7.7) from aftershock observations: A high stress drop event

2002 ◽  
Vol 29 (20) ◽  
pp. 10-1-10-4 ◽  
Author(s):  
H. Negishi ◽  
J. Mori ◽  
T. Sato ◽  
R. Singh ◽  
S. Kumar ◽  
...  
Keyword(s):  
Stress Drop ◽  
Fault Plane ◽  
High Stress

scholarly journals Stress Drop, Seismogenic Index and Fault Cohesion of Fluid-Induced Earthquakes

2021 ◽  
Author(s):  
Serge A. Shapiro ◽  
Carsten Dinske
Keyword(s):  
Stress Drop ◽  
Induced Seismicity ◽  
Quantitative Characteristic ◽  
High Stress ◽  
Operation Time ◽  
Average Stress ◽  
Induced Earthquakes ◽  
Effective Stresses ◽  
Seismicity Rates

AbstractSometimes, a rather high stress drop characterizes earthquakes induced by underground fluid injections or productions. In addition, long-term fluid operations in the underground can influence a seismogenic reaction of the rock per unit volume of the fluid involved. The seismogenic index is a quantitative characteristic of such a reaction. We derive a relationship between the seismogenic index and stress drop. This relationship shows that the seismogenic index increases with the average stress drop of induced seismicity. Further, we formulate a simple and rather general phenomenological model of stress drop of induced earthquakes. This model shows that both a decrease of fault cohesion during the earthquake rupture process and an enhanced level of effective stresses could lead to high stress drop. Using these two formulations, we propose the following mechanism of increasing induced seismicity rates observed, e.g., by long-term gas production at Groningen. Pore pressure depletion can lead to a systematic increase of the average stress drop (and thus, of magnitudes) due to gradually destabilizing cohesive faults and due to a general increase of effective stresses. Consequently, elevated average stress drop increases seismogenic index. This can lead to seismic risk increasing with the operation time of an underground reservoir.

A dynamic source model for the San Fernando earthquake

1978 ◽  
Vol 68 (6) ◽  
pp. 1555-1576
Author(s):  
Michel Bouchon
Keyword(s):  
Fault Plane ◽  
High Stress ◽  
Time History ◽  
High Strength ◽  
High Amplitude ◽  
Tectonic Stress ◽  
Source Model ◽  
Dynamic Crack ◽  
San Fernando ◽  
High Level

abstract We model the San Fernando earthquake as a propagating rupture in a half-space, using for the slip-time-history on the fault plane analytical expressions which approximate the slip functions of dynamic crack models obtained by Das and Aki (1977a, b). We synthesize the strong ground motions and accelerations at the Pacoima Dam site and compute the teleseismic signals for different models of cracks. Three major featuras of the data–the strong pulse associated with the beginning of the rupture, the high acceleration phase on the Pacoima Dam records, and the presence of ripples on the teleseismic seismograms–which are not compatible with a smooth rupture process, are well explained by a crack with barriers model where the rupture encounters, along the fault plane, barriers or obstacles of high strength materials which may remain unbroken after the passage of the rupture front. A high-stress drop (400 to 500 bars) is required in the hypocentral area to explain the high-amplitude short-duration first pulse of the teleseismic records. This indicates a high level of tectonic stress in the area. A study of the earthquake series following the main shock shows that the aftershocks which took place in the region where major slipping occurred during the earthquake may represent the release of some of the barriers.

P-wave spectra for ML 5 foreshocks, aftershocks, and isolated earthquakes near Parkfield, California

1981 ◽  
Vol 71 (2) ◽  
pp. 423-436
Author(s):  
Willian H. Bakun ◽  
Thomas V. McEvilly
Keyword(s):  
Stress Drop ◽  
High Stress ◽  
P Wave ◽  
Wave Radiation ◽  
Focal Region ◽  
Wave Spectra ◽  
Rupture Length ◽  
Main Shocks ◽  
Relative Stress ◽  
Fault Trace

abstract Wood-Anderson seismograms recorded at Mount Hamilton (MHC, 185 km, 327°), Santa Barbara (SBC, 180 km, 158°), and Tinemaha (TIN, 240 km, 56°) provide data for comparing P-wave spectra for two immediate (17-min) foreshocks, one early (55-hr) foreshock, two aftershocks, and two “isolated” Parkfield earthquakes. All are ML 5.0 shocks with epicenters within 7 km of the common epicenter of the 1934 and 1966 Parkfield main shocks. The set of events is well suited for testing the hypothesis that foreshocks are high-stress-drop sources. Calculated stress drops are controlled by source directivity at azimuths aligned with the fault break (at MHC and SBC). P-wave radiation from the three foreshocks is focused along one fault trace azimuth, suggesting that foreshock sources are characterized by pronounced unilateral rupture expansion. At TIN, broadside to the fault where directivity has minimum effect on calculated relative stress drop, the two immediate foreshocks are higher stress-drop sources. The early foreshock is a low-to-average stress-drop source, indicating the possibility that stress concentration is a rapidly occurring phenomenon in rupture nucleation. Alternatively, the stress field is highly variable on the scale of 2 to 3 km in the focal region of an impending earthquake with a rupture length of 20 to 30 km.

Evaluation of static stress on a fault plane from a Green's function

1974 ◽  
Vol 64 (6) ◽  
pp. 1629-1633
Author(s):  
D. J. Andrews
Keyword(s):  
Shear Strain ◽  
Green's Function ◽  
Plane Stress ◽  
Representation Theorem ◽  
Stress Drop ◽  
Numerical Evaluation ◽  
Analytic Solution ◽  
Fault Plane ◽  
Static Stress ◽  
Field Point

abstract Direct numerical evaluation of shear strain on a fault plane using the representation theorem is not possible because source points near the field point give large and canceling contributions to the integral. The representation theorem for strain can be integrated by parts to obtain an expression valid everywhere and suitable for numerical evaluation on the fault plane. Stress-drop evaluated by this method for the circular dislocation of Keylis-Borok agrees well with the analytic solution.

Improved approach for stress drop estimation and its application to an induced earthquake sequence in Oklahoma

2020 ◽  
Vol 223 (1) ◽  
pp. 233-253
Author(s):  
X Chen ◽  
R E Abercrombie
Keyword(s):  
Stress Drop ◽  
Source Parameters ◽  
High Stress ◽  
Temporal Variations ◽  
Earthquake Source ◽  
Average Stress ◽  
Corner Frequency ◽  
Resolution Limit ◽  
Spectral Fitting ◽  
Spatio Temporal

SUMMARY We calculate source parameters for fluid-injection induced earthquakes near Guthrie, Oklahoma, guided by synthetic tests to quantify uncertainties. The average stress drop during an earthquake is a parameter fundamental to ground motion prediction and earthquake source physics, but it has proved hard to measure accurately. This has limited our understanding of earthquake rupture, as well as the spatio-temporal variations of fault strength. We use synthetic tests based on a joint spectral-fitting method to define the resolution limit of the corner frequency as a function of the maximum frequency of usable signal, for both individual spectra and the average from multiple stations. Synthetic tests based on stacking analysis find that an improved stacking approach can recover the true input stress drop if the corner frequencies are within the resolution limit defined by joint spectral-fitting. We apply the improved approach to the Guthrie sequence, using different wave types and signal-to-noise criteria to understand the stability of the calculated stress drop values. The results suggest no systematic scaling relationship of stress drop for M ≤ 3.1 earthquakes, but larger events (M ≥ 3.5) tend to have higher average stress drops. Some robust spatio-temporal variations can be linked to the triggering processes and indicate possible stress heterogeneity within the fault zone. Tight clustering of low stress drop events at the beginning stage of the sequence suggests that pore pressure influences earthquake source processes. Events at shallow depth have lower stress drop compared to deeper events. The largest earthquake occurred within a cluster of high stress drop events, likely rupturing a strong asperity.

scholarly journals Ice Stream C, Antarctica, sticky spots detected by microearthquake monitoring

1994 ◽  
Vol 20 ◽  
pp. 183-186 ◽  
Author(s):  
S. Anandakrishnan ◽  
R. B. Alley
Keyword(s):  
Shear Stress ◽  
Stress Drop ◽  
Fast Moving ◽  
Fault Plane ◽  
Spatial Density ◽  
Ice Stream ◽  
Slow Moving ◽  
Ice Stream B ◽  
Basal Shear ◽  
Plane Area

Microearthquakes at the base of slow-moving Ice Stream C occur many times more frequently than at the base of fast-moving Ice Stream B. We suggest that the microearthquake source sites are so-called “sticky spots”, defined as limited zones of stronger Subglacial material interspersed within a weaker matrix. The fault-plane area of the microearthquakes (O(102m2)) is therefore a measure of the size of the sticky spots. The spatial density of the microearthquakes (O(10 km-2)) is a measure of the distribution of sticky spots.The average stress drop associated with these microearthquakes is consistent with an ice-stream bed model of weak subglacial till interspersed with stronger zones that support much or all of the basal shear stress. We infer a weak inter-sticky-spot material by the large distances (O(103m)), relative to fault radius, to which the microearthquake stress change is transmitted.

scholarly journals Study of fault plane solutions and stress drop using local broadband network data: The 2011 Sikkim Himalaya earthquake Mw 6.9 and its aftershocks

2018 ◽  
Vol 61 (1) ◽  
Author(s):  
Santanu Baruah ◽  
Sebastiano D’Amico ◽  
Sowrav Saikia ◽  
J Gautam ◽  
R. K. Devi ◽  
...  
Keyword(s):  
Stress Drop ◽  
Fault Plane ◽  
Network Data ◽  
Fault Plane Solutions ◽  
Sikkim Himalaya ◽  
Broadband Network

scholarly journals Deterministic Investigation of Effect of Stress Drop on Seismic Site Response Analysis of Allahabad City

2020 ◽  
Author(s):  
Keshav Kumar Sharma ◽  
Kumar Pallav ◽  
Shashi Kant Duggal
Keyword(s):  
Stress Drop ◽  
Site Response ◽  
High Stress ◽  
Site Response Analysis ◽  
Response Analysis ◽  
Contour Plot ◽  
Spectral Acceleration ◽  
Ground Acceleration ◽  
Seismic Site Response ◽  
Finite Fault

Abstract Due to the high stress of Faizabad ridge close to Allahabad city and the absence of strong-motion records for any engineering studies, it is essential to use a stochastic model to study the deterministic earthquake scenario of Allahabad city. The work investigates the effect of stress drop for an earthquake on 30 sites (83 boreholes) located across the city using 1-D seismic site response analysis. The ground motion has been simulated for Allahabad fault using stochastic finite fault model for stress drop ranges from ~70 bar to ~200 bars. Simulation results show the Peak Ground Acceleration (PGA) value of 0.026 g and 0.085 g at 70 and 200 bars stress drops, respectively. Site response results reveal that Indian Standard IS: 1893-2002 underestimates the PGA at higher stress drop compared to the estimated spectral acceleration values. Further, the lower stress drop can give a higher mean spectral acceleration at a long-period. Contour plot of surface-level PGA, low and high period spectral acceleration with response spectra for Allahabad city shows the variation with stress drop.

Modeling of source rupture characteristics for the Saguenay earthquake of November 1988

1995 ◽  
Vol 85 (2) ◽  
pp. 525-551 ◽  
Author(s):  
R. A. W. Haddon
Keyword(s):  
North America ◽  
Stress Drop ◽  
High Stress ◽  
Strong Motion ◽  
Eastern North America ◽  
Fault Rupture ◽  
Rupture Area ◽  
Past Half Century ◽  
Acceleration Data ◽  
Strong Ground

Abstract The magnitude mb = 6.0 Saguenay earthquake of 25 November 1988 in Quebec, Canada, was one of the largest to have occurred in eastern North America during the past half-century. Recorded high-frequency ground motions exceeded anticipated values for an event of its size by a factor of 10 on both the regional network and strong-motion instruments. Two proposed explanations for the discrepancy are (1) that the source was a rare “high stress drop” event and (2) that it was an asymmetrical “fractional stress drop” rupture (involving only normal effective stresses). In this article, detailed fault-slip models are derived to fit characteristics of strong-motion displacement, velocity, and acceleration data. The results establish that the effective rupture stress was normal (less than 100 bars), that the fault rupture was highly asymmetrical with respect to the point of rupture initiation, and that the average slip time for points within the rupture area (approx. 0.2 sec) was considerably less than that associated with the standard Brune (1970) source spectral model. The rupture area developed in a number of episodes, each widening or lengthening the previously ruptured area, which may explain the short average slip time. The results indicate that the widely used assumption in hazard analyses that earthquake spectra are adequately represented by the standard Brune (1970) complete stress drop model may be seriously unreliable for prediction of strong ground motion in eastern North America.

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