SCEC Award Number 20163 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title SCEC BBP Enhancement: Scenario Validation Plus Implementation of a Broadband 3D Kinematic Rupture Generator
Name Organization
Kim Olsen San Diego State University
Other Participants PhD Candidate Nan Wang
SCEC Priorities 4a, 4b, 4c SCEC Groups GM, CS, Seismology
Report Due Date 03/15/2021 Date Report Submitted 05/14/2021
Project Abstract
Spontaneous rupture simulations along geometrically rough faults have been shown to produce realistic far‐field spectra and comparable fits with ground motion metrics such as spectral accelerations and peak motions from Ground Motion Prediction Equations (GMPEs), but they are too computationally demanding for use with physics‐based probabilistic seismic hazard analysis efforts. Here, we present our implementation of a kinematic rupture generator that matches the characteristics of, at least in a statistical sense, rough‐fault spontaneous rupture models. To this end, we analyze ~100 dynamic rupture simulations on strike‐slip faults with Mw ranging from 6.4 to 7.2. We find that our dynamic simulations follow empirical scaling relationships for strike‐slip events and provide source spectra comparable to a source model with ω−2 decay. To define our kinematic source model, we use a regularized Yoffe function parameterized in terms of slip, peak‐time, rise‐time, and rupture initiation time.
These parameters are defined through empirical relationships with random fields whose one‐ and two‐point statistics are derived from the dynamic rupture simulations. Our rupture generator reproduces Next Generation Attenuation (NGA) West2 GMPE medians and intraevent standard deviations of spectral accelerations with periods as short as 0.2 s for ensembles of ground motion simulations. Our rupture generator produces kinematic source models for M6.4–7.2 strike‐slip scenarios that can be used in broadband physics‐based probabilistic seismic hazard efforts or to supplement data in areas of limited observations for the development of future GMPEs.
Intellectual Merit The underlying statistical basis for the new Savran-Olsen kinematic rupture generator (SO-KRG) goes considerably beyond any previous methods in seismic hazard computation. The method mimics, at least in a statistical sense, the processes of rough-fault spontaneous rupture models in order to generate broadband source models, and illustrates how additional physics can be incorporated into the process of generating seismic source models.
Broader Impacts The new rupture generator is developed with particular attention to realistic high-frequency content in the resulting source models, which is an increasingly important point as supercomputers allow for greater resolution in the hazard models. For that reason, and dependent on the ongoing validation, the rupture generator could become invaluable for future hazard calculations.

The project funded two PhD students toward their thesis work.
Exemplary Figure Figure 2. Comparisons of KRG-produced spectral accelerations to NGA-W2 at (left) 0.5 Hz and (center) 5 Hz, and (right) example of simulated far-field acceleration spectra. The vertical dashed line depicts the f_max=10 Hz of our deterministic simulations, and the thick dashed line shows the ω^0 high-frequency decay.