Properties of dynamic earthquake ruptures with heterogeneous stress drop

Ampuero, Jean‐Paul; Ripperger, J.; M, Prof. Redhya

doi:10.1029/170gm25

Cited by 49 publications

(58 citation statements)

References 20 publications

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“…Thus, apart from the probability density function (pdf), the random stress fields are controlled by the three parameters H , a c and std, where a c denotes the correlation length a c = 2 π / k c . This parameter also appears in the spectral description of von Karman fields adopted by Mai and Beroza [2002] and Ampuero et al [2006]. Variations of these three parameters will be studied in the main part of this paper.…”

Section: Methodsmentioning

confidence: 99%

Earthquake source characteristics from dynamic rupture with constrained stochastic fault stress

et al. 2007

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[1] One of the challenging tasks in predicting near-source ground motion for future earthquakes is to anticipate the spatiotemporal evolution of the rupture process. The final size of an event but also its temporal properties (propagation velocity, slip velocity) depend on the distribution of shear stress on the fault plane. Though these incipient stresses are not known for future earthquakes, they might be sufficiently well characterized in a stochastic sense. We examine the evolution of dynamic rupture in numerical models of a fault subjected to heterogeneous stress fields with varying statistical properties. By exploring the parameter space of the stochastic stress characterization for a large number of random realizations we relate generalized properties of the resulting events to the stochastic stress parameters. The nucleation zone of the simulated earthquake ruptures in general has a complex shape, but its average size is found to be independent of the stress field parameterization and is determined only by the material parameters and the friction law. Furthermore, we observe a sharp transition in event size from small to system-wide events, governed mainly by the standard deviation of the stress field. A simplified model based on fracture mechanics is able to explain this transition. Finally, we find that the macroscopic rupture parameters (e.g., moment, moment rate, seismic energy) of our catalog of model quakes are generally consistent with observational data.Citation: Ripperger, J., J.-P. Ampuero, P. M. Mai, and D. Giardini (2007), Earthquake source characteristics from dynamic rupture with constrained stochastic fault stress,

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Section: Methodsmentioning

confidence: 99%

Earthquake source characteristics from dynamic rupture with constrained stochastic fault stress

et al. 2007

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“…These include the nucleation of earthquakes and foreshocks driven by stress concentration near the boundaries between creeping and locked fault areas, for example at the base of the seismogenic zone; the initiation of frictional sliding near point loads in laboratory experiments (Rubinstein et al 2007;Kammer et al 2014); induced seismicity near concentrated loads generated by fluid injection (Garagash & Germanovich 2012), and the initiation of landslides by locally elevated pore pressures (Viesca & Rice 2012). The overstressed asperity initiation is admittedly a crude representation of these situations, but it encapsulates some of their key physical ingredients and hence is a basic model that can provide insight into more realistic situations, as illustrated by the work of Ampuero et al (2006) and Ripperger et al (2007).…”

Section: O N C L U S I O N Smentioning

confidence: 99%

“…Campillo & Ionescu 1997;Ampuero et al 2002;Uenishi & Rice 2003) established critical length scales for the onset of self-accelerating slip, but did not consider whether the rupture became indefinitely selfsustained or arrested spontaneously at some (possibly large) distance from the nucleation area. The transition from spontaneously arresting to self-sustained ruptures has been studied under slipweakening friction by Ampuero et al (2006), Viesca & Rice (2012) and Garagash & Germanovich (2012) in 2-D, and by Ripperger et al (2007) in 3-D. Our first goal is to determine the sufficient ('critical') conditions to initiate sustained ruptures, that is, ruptures on faults with uniform background stress that propagate indefinitely unless they encounter a high strength barrier.…”

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On the initiation of sustained slip-weakening ruptures by localized stresses

Gális

Pelties

Kristek

et al. 2014

Geophysical Journal International

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S U M M A R YNumerical simulations of dynamic earthquake rupture require an artificial initiation procedure, if they are not integrated in long-term earthquake cycle simulations. A widely applied procedure involves an 'overstressed asperity', a localized region stressed beyond the static frictional strength. The physical properties of the asperity (size, shape and overstress) may significantly impact rupture propagation. In particular, to induce a sustained rupture the asperity size needs to exceed a critical value. Although criteria for estimating the critical nucleation size under linear slip-weakening friction have been proposed for 2-D and 3-D problems based on simplifying assumptions, they do not provide general rules for designing 3-D numerical simulations. We conduct a parametric study to estimate parameters of the asperity that minimize numerical artefacts (e.g. changes of rupture shape and speed, artificial supershear transition, higher slip-rate amplitudes). We examine the critical size of square, circular and elliptical asperities as a function of asperity overstress and background (off-asperity) stress. For a given overstress, we find that asperity area controls rupture initiation while asperity shape is of lesser importance. The critical area obtained from our numerical results contrasts with published theoretical estimates when background stress is low. Therefore, we derive two new theoretical estimates of the critical size under low background stress while also accounting for overstress. Our numerical results suggest that setting the asperity overstress and area close to their critical values eliminates strong numerical artefacts even when the overstress is large. We also find that properly chosen asperity size or overstress may significantly shorten the duration of the initiation. Overall, our results provide guidelines for determining the size of the asperity and overstress to minimize the effects of the forced initiation on the subsequent spontaneous rupture propagation.

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“…Recent studies by Ampuero et al (2006) and Ripperger et al (2007) explored the stochastic parameterization of initial shear stress for simulations of dynamic earthquake rupture. These papers mainly investigated the modeled rupture process on the fault plane, but because the approach ultimately aims at improving seismic hazard assessment, it is mandatory to verify the ground motions predicted by these simulations against observations.…”

Section: Introductionmentioning

confidence: 99%

Variability of Near-Field Ground Motion from Dynamic Earthquake Rupture Simulations

Ripperger¹,

M²,

Ampuero³

2008

Bulletin of the Seismological Society of America

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This study investigates near-field ground-motion variability due to dynamic rupture models with heterogeneity in the initial shear stress. Ground velocity seismograms are synthesized by convolving the time histories of slip velocity obtained from spontaneous dynamic rupture models with Green's functions of the medium calculated with a discrete wavenumber/finite-element method. Peak ground velocity (PGV) estimated on the synthetics generally matches well with an empirically derived attenuation relation, whereas spectral acceleration (SA) shows only an acceptable match at periods longer than 1 sec. Using the geometric mean to average the two orthogonal components leads to a systematic bias for the synthetics, in particular at the stations closest to the fault. This bias is avoided by using measures of ground motion that are independent of the sensor orientation.The contribution from stress heterogeneity to the overall ground-motion variability is found to be strongest close to the fault and in the backward directivity region of unilaterally propagating ruptures. In general, the intraevent variability originating from the radiation pattern and the effect of directivity is on the same order or larger than the interevent variability. The interevent ground-motion variability itself is dominated by the hypocenter-station configuration and is influenced only to a lesser extent by the differences in the dynamic rupture process due to the stress heterogeneity. In our modeling approach the hypocenter location is not picked arbitrarily but is determined to be mechanically consistent with the stress heterogeneity through a procedure emulating tectonic stress loading of the fault and nucleation. Compared to the peak ground motion recorded during the 2004 Parkfield, California, earthquake our simulated seismograms show enhanced spatial correlation that may be attributed to the simplicity of the assumed crustal model or to an incomplete representation of the spatial heterogeneity of dynamic rupture parameters. Nevertheless, the intraevent PGV variability in the near-fault region determined for the Parkfield dataset is of the same order of magnitude as for our simulations.

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Properties of dynamic earthquake ruptures with heterogeneous stress drop

Cited by 49 publications

References 20 publications

Earthquake source characteristics from dynamic rupture with constrained stochastic fault stress

Earthquake source characteristics from dynamic rupture with constrained stochastic fault stress

On the initiation of sustained slip-weakening ruptures by localized stresses

Variability of Near-Field Ground Motion from Dynamic Earthquake Rupture Simulations

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