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A method to generate initial fault stresses for physics-based ground motion prediction consistent with regional seismicity

Oral, Elif and Ampuero, Jean Paul and Ruiz, Javier and Asimaki, Domniki (2022) A method to generate initial fault stresses for physics-based ground motion prediction consistent with regional seismicity. . (Unpublished)

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Near-field ground motion is the major blind spot of seismic hazard studies, mainly because of the challenges in accounting for source effects. Initial stress heterogeneity is an important component of physics-based approaches to ground motion prediction that represent source effects through dynamic earthquake rupture modeling. We hypothesize that stress heterogeneity on a fault primarily originates from past background seismicity. We develop a new method to generate stochastic stress distributions as a superposition of residual stresses left by previous ruptures that are consistent with regional distributions of earthquake size and hypocentral depth. We validate our method on M_w 7 earthquake models suitable for California, by obtaining a satisfactory agreement with empirical earthquake scaling laws and ground motion prediction equations. To avoid the excessive seismic radiation produced by dynamic models with abrupt arrest at preset rupture borders, we achieve spontaneous rupture arrest by incorporating a scale-dependent fracture energy adjusted with fracture mechanics theory. Our analyses of rupture and ground motion reveal particular signatures of the initial stress heterogeneity: rupture can locally propagate at supershear speed near the highly-stressed areas; the position of high-stress and low-stress areas due to initial stress heterogeneity determines how the peak ground motion amplitudes and polarization spatially vary along the fault, as low-stress areas slows down the rupture, decrease stress drop, and change the radiation distribution before the rupture arrest. We also find that the medium stratification amplifies the moment rate spectrum at frequencies above 2 Hz, which requires understanding the interaction between site effects and rupture dynamics; therefore, we highlight the need to consider a realistic fault medium on future studies of rupture dynamics. Our approach advances our understanding of the relations between dynamic features of earthquake ruptures and the statistics of regional seismicity, and our capability to model source effects for near-field ground motion prediction studies.

Item Type:Report or Paper (Discussion Paper)
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URLURL TypeDescription Paper ItemSPECFEM3D ItemCode modifications Information
Oral, Elif0000-0003-1081-5580
Ampuero, Jean Paul0000-0002-4827-7987
Asimaki, Domniki0000-0002-3008-8088
Additional Information:This work has been supported by the French government, through the UCAJEDI Investments in the Future project managed by the National Research Agency (ANR) with the reference number ANR-15-IDEX-01, Southern California Earthquake Center award 21010, and the California Institute of Technology. The computations presented here were conducted in the Thera cluster of Geoazur, and the Resnick High Performance Computing Center, a facility supported by Resnick Sustainability Institute at the California Institute of Technology. We acknowledge Caroline Ramel for IT support, and SCEC DRV benchmark participants and Yihe Huang for valuable discussions. Data and resources. SPECFEM3D is available at The modifications that we made can be found upon the publication of our manuscript. The supplemental material includes one section of homogeneous models and thirty figures.
Group:Seismological Laboratory, Resnick Sustainability Institute
Funding AgencyGrant Number
Agence Nationale pour la Recherche (ANR)ANR-15-IDEX-01
Southern California Earthquake Center (SCEC)21010
Record Number:CaltechAUTHORS:20220520-388187000
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:114834
Deposited By: George Porter
Deposited On:23 May 2022 19:36
Last Modified:23 May 2022 19:36

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