SCEC Award Number 21111 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Modeling of the 2019 M7.1 Ridgecrest, CA, Earthquake, Including a Data-constrained Fault Zone
Investigator(s)
Name Organization
Kim Olsen San Diego State University
Other Participants Te-Yang Yeh, PhD student
SCEC Priorities 4a, 4b, 4c SCEC Groups GM, CS, Seismology
Report Due Date 03/15/2022 Date Report Submitted 03/17/2022
Project Abstract
 We continue our 3D deterministic modeling of the July 2019 M7.1 Ridgecrest, CA, earthquake. We use the GPU-enabled (Cui et al., 2013) version of AWP (AWP-GPU), and map the contributions to the ground motions from surface topography, Q(f), and small-scale heterogeneities. Inclusion of the effects of the low near-surface material (Vs(min)=300 m/s) is enabled using the discontinuous-mesh version of AWP (Nie et al., 2017). We use kinematic rupture models from source inversion, enriched in higher frequency signal. We include a model of the fault damage zone adapted from Zhou et al. (2022) from ambient noise cross correlation, which generally improves the fit to data, by increasing the peak ground velocities (PGVs, at select sites by more than 50%) and Fourier Amplitude Spectra (FAS). We find that in general, the best fit to the data is obtained by including both the damage zone and a shallow (<700 m) geotechnical layer (GTL). Simulations including nonlinear (plastic) effects following Drucker-Prager rheology shows reduction of PGVs and peak ground accelerations (PGAs) in the fault zone, in particular in the southern end, by up a factor of 2. However, the far-field waves from the M7.1 Ridgecrest earthquake are not significantly affected by plastic effects in the damage zone.
Intellectual Merit We have shown that it is important to include a model of the fault damage zone as well as a shallow (<700 m) geotechnical layer (GTL), which both contributes to improve the accuracy of the ground motion simulations of the M7.1 Ridgecrest earthquake. Nonlinear (plastic) effects following Drucker-Prager rheology causes reduction of PGVs by up to a factor of 2 in the fault zone, in particular in the southern end. The far-field waves from the M7.1 Ridgecrest earthquake are not significantly affected by plastic effects in the damage zone. These finds provide useful guidelines for future ground motion simulations, of the Ridgecrest event and other earthquakes.
Broader Impacts Improved accuracy of ground motion simulations inevitably leads to more accurate seismic hazard analysis and reduction of loss of life and property in future events.
Exemplary Figure Figure 6. Comparison of (top) PGV and (bottom) PGA computed for models with (left) CVMSI only, (center) CVMSI+fault zone, and (right) CVMSI+Fault zone+GTL. The attenuation model for all solutions is Qs = 0.075 Vs f^0.