scholarly journals Fault roughness and strength heterogeneity control earthquake size and stress drop

2017 ◽  
Vol 44 (2) ◽  
pp. 777-783 ◽  
Author(s):  
O. Zielke ◽  
M. Galis ◽  
P. M. Mai
Keyword(s):  
Stress Drop ◽  
Fault Roughness ◽  
Earthquake Size

Stress Drop during Earthquakes: Effect of Fault Roughness Scaling

2011 ◽  
Vol 101 (5) ◽  
pp. 2369-2387 ◽  
Author(s):  
T. Candela ◽  
F. Renard ◽  
M. Bouchon ◽  
J. Schmittbuhl ◽  
E. E. Brodsky
Keyword(s):  
Stress Drop ◽  
Fault Roughness

On the heterogeneity of the earthquake rupture

2020 ◽  
Author(s):  
Luca Malagnini ◽  
Douglas S Dreger ◽  
Robert M Nadeau ◽  
Irene Munafò ◽  
Massimo Cocco
Keyword(s):  
Stress Drop ◽  
Seismic Moment ◽  
Corner Frequency ◽  
Self Similarity ◽  
Earthquake Parameters ◽  
Scaling Models ◽  
Elastic Rebound ◽  
Earthquake Size ◽  
Source Models ◽  
Slip Area

Summary The scaling of earthquake parameters with seismic moment and its interpretation in terms of self-similarity is still debated in the literature. We address this question by examining a worldwide compilation of corner frequency-based and elastic rebound theory (ERT)-based fault slip, area and stress drop values for earthquakes ranging in magnitude from -0.7 to 7.8. We find that corner frequency estimates of slip (and stress drop) scale differently than those inferred from the ERT approach, where the latter deviates from the generally accepted constant stress drop behavior of so-called self-similar scaling models. We also find that average slips from finite-source models are consistent with corner frequency scaling, whereas peak slip values are more consistent with the ERT scaling. The different scaling of corner frequency- and ERT-based estimates of slip and stress drop with earthquake size is interpreted in terms of heterogeneity of the rupture process. ERT-based estimates of stress drop decrease with seismic moment suggesting a self-affine behavior. Despite the inferred heterogeneity at all scales, we do not observe a clear effect on the Brune stress drop scaling with earthquake size.

Upper bounds on near-source peak ground motion based on a model of inhomogeneous faulting

1982 ◽  
Vol 72 (6A) ◽  
pp. 1825-1841
Author(s):  
A. McGarr
Keyword(s):  
Ground Motion ◽  
Stress Drop ◽  
Source Region ◽  
Seismic Source ◽  
Theoretical Argument ◽  
Peak Acceleration ◽  
Data Set ◽  
State Of Stress ◽  
Earthquake Size ◽  
Reported Data

abstract Two independent arguments indicate an upper bound of about 10 for the ratio ro/ri in the expressions for peak velocity v and peak acceleration a at close hypocentral distances R: v = (βΔτro/μR)[0.10(ro/ri) + 0.15] and a = (Δτ/ρR)[0.30(ro/ri)2 + 0.45], where ri is the radius of the most heavily loaded asperity that fails within an earthquake source region of radius ro, Δτ is the stress drop, β is the shear-wave velocity, μ is the modulus of rigidity, and ρ is the density; these relationships are for ground motion recorded in a whole-space. First, a recently reported data set was augmented by observations for six earthquakes in the magnitude range 4 ≦ ML ≦ 6.6, for which ground motion was recorded at a minimum of five sites at hypocentral distances of the order of 10 km; the new events include the 1979 Coyote Lake and 1979 Imperial Valley shocks. The entire data set of 22 events, spanning a range in seismic moment from 5 × 1016 to over 1026 dyne-cm, is consistent both with the bound ro/ri < 10 and with the previous conclusion that this ratio does not depend systematically on earthquake size. Second, a theoretical argument, using the result of Savage and Wood that the apparent stress acting on the earthquake fault plane is less than half of the stress drop, is made to the effect that ro/ri < 10. In addition, absolute limits, independent of earthquake size, for peak acceleration are related to the state of stress in the crust; for an extensional state of stress a ≦ 0.40 g and for a compressional stress state a ≦ 2.0 g, where a now represents the maximum horizontal acceleration as recorded at the surface directly above the seismic source.

scholarly journals Stress drop–magnitude dependence of acoustic emissions during laboratory stick-slip

2020 ◽  
Vol 224 (2) ◽  
pp. 1371-1380
Author(s):  
Aglaja Blanke ◽  
Grzegorz Kwiatek ◽  
Thomas H W Goebel ◽  
Marco Bohnhoff ◽  
Georg Dresen
Keyword(s):  
Grain Size ◽  
Stress Drop ◽  
Source Parameters ◽  
Corner Frequency ◽  
Strong Increase ◽  
Stick Slip ◽  
Fault Roughness ◽  
Average Grain Size ◽  
Seismic Stress ◽  
Stress Drops

SUMMARY Earthquake source parameters such as seismic stress drop and corner frequency are observed to vary widely, leading to persistent discussion on potential scaling of stress drop and event size. Physical mechanisms that govern stress drop variations are difficult to evaluate in nature and are more readily studied in controlled laboratory experiments. We perform two stick-slip experiments on fractured (rough) and cut (smooth) Westerly granite samples to explore fault roughness effects on acoustic emission (AE) source parameters. We separate large stick-slip events that generally saturate the seismic recording system from populations of smaller AE events which are sensitive to fault stresses prior to slip. AE event populations show many similarities to natural seismicity and may be interpreted as laboratory equivalent of natural microseismic events. We then compare the temporal evolution of mechanical data such as measured stress release during slip to temporal changes in stress drops derived from AEs using the spectral ratio technique. We report on two primary observations: (1) In contrast to most case studies for natural earthquakes, we observe a strong increase in seismic stress drop with AE size. (2) The scaling of stress drop with magnitude is governed by fault roughness, whereby the rough fault shows a more rapid increase of the stress drop–magnitude relation with progressing large stick-slip events than the smooth fault. The overall range of AE sizes on the rough surface is influenced by both the average grain size and the width of the fault core. The magnitudes of the smallest AE events on smooth faults may also be governed by grain size. However, AEs significantly grow beyond peak roughness and the width of the fault core. Our laboratory tests highlight that source parameters vary substantially in the presence of fault zone heterogeneity (i.e. roughness and narrow grain size distribution), which may affect seismic energy partitioning and static stress drops of small and large AE events.

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.

Damage of Short-Fiber-Reinforced Metal Matrix Composites Considering Cooling and Thermal Cycling

1999 ◽  
Vol 122 (2) ◽  
pp. 203-208 ◽  
Author(s):  
Chuwei Zhou ◽  
Wei Yang ◽  
Daining Fang
Keyword(s):  
Thermal Cycling ◽  
Metal Matrix Composites ◽  
Stress Drop ◽  
Metal Matrix ◽  
Failure Modes ◽  
Short Fiber ◽  
Uniaxial Tensile ◽  
Matrix Composites ◽  
Fiber Reinforced ◽  
Matrix Damage

Mechanical properties and damage evolution of short-fiber-reinforced metal matrix composites (MMC) are studied under a micromechanics model accounting for the history of cooling and thermal cycling. A cohesive interface is formulated in conjunction with the Gurson-Tvergaard matrix damage model. Attention is focused on the residual stresses and damages by the thermal mismatch. Substantial stress drop in the uniaxial tensile response is found for a computational cell that experienced a cooling process. The stress drop is caused by debonding along the fiber ends. Subsequent thermal cycling lowers the debonding stress and the debonding strain. Micromechanics analysis reveals three failure modes. When the thermal histories are ignored, the cell fails by matrix damage outside the fiber ends. With the incorporation of cooling, the cell fails by fiber end debonding and the subsequent transverse matrix damage. When thermal cycling is also included, the cell fails by jagged debonding around the fiber tops followed by necking instability of matrix ligaments. [S0094-4289(00)01202-0]

Strain to Ground Motion Conversion of DAS Data for Earthquake Magnitude and Stress Drop Determination

2021 ◽  
Author(s):  
Itzhak Lior ◽  
Anthony Sladen ◽  
Diego Mercerat ◽  
Jean-Paul Ampuero ◽  
Diane Rivet ◽  
...  
Keyword(s):  
Early Warning ◽  
Stress Drop ◽  
Source Parameters ◽  
Simulated Data ◽  
Earthquake Early Warning ◽  
Body Waves ◽  
Ocean Bottom ◽  
Correlated Noise ◽  
S Wave ◽  
Earthquake Source Parameters

<p>The use of Distributed Acoustic Sensing (DAS) presents unique advantages for earthquake monitoring compared with standard seismic networks: spatially dense measurements adapted for harsh environments and designed for remote operation. However, the ability to determine earthquake source parameters using DAS is yet to be fully established. In particular, resolving the magnitude and stress drop, is a fundamental objective for seismic monitoring and earthquake early warning. To apply existing methods for source parameter estimation to DAS signals, they must first be converted from strain to ground motions. This conversion can be achieved using the waves’ apparent phase velocity, which varies for different seismic phases ranging from fast body-waves to slow surface- and scattered-waves. To facilitate this conversion and improve its reliability, an algorithm for slowness determination is presented, based on the local slant-stack transform. This approach yields a unique slowness value at each time instance of a DAS time-series. The ability to convert strain-rate signals to ground accelerations is validated using simulated data and applied to several earthquakes recorded by dark fibers of three ocean-bottom telecommunication cables in the Mediterranean Sea. The conversion emphasizes fast body-waves compared to slow scattered-waves and ambient noise, and is robust even in the presence of correlated noise and varying wave propagation directions. Good agreement is found between source parameters determined using converted DAS waveforms and on-land seismometers for both P- and S-wave records. The demonstrated ability to resolve source parameters using P-waves on horizontal ocean-bottom fibers is key for the implementation of DAS based earthquake early warning, which will significantly improve hazard mitigation capabilities for offshore and tsunami earthquakes.</p>

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