Non-ergodic PSHA using fully-deterministic physics-based models for Southern California

Scott Callaghan, Kevin R. Milner, Christine A. Goulet, Bruce E. Shaw, Philip J. Maechling, Kim B. Olsen, Robert W. Graves, Karan Vahi, Ewa Deelman, Thomas H. Jordan, & Yehuda Ben-Zion

Published April 21, 2022, SCEC Contribution #12630

The CyberShake platform, developed by the Southern California Earthquake Center, performs physics-based probabilistic seismic hazard analysis using 3D wave propagation simulations with reciprocity. One of the key inputs to CyberShake is the earthquake rupture forecast (ERF). Previous regional CyberShake studies have used an ERF derived from UCERF2, extended with a kinematic rupture generator. Here we investigate the impact of using a fully physics-based ERF created with the Rate-State Earthquake Simulator (RSQSim) software. We used RSQSim to generate a 715,000-year rupture catalog for the UCERF3 fault system that includes full slip-time histories along fault planes. Building on the work in Milner et al. (2021), we performed CyberShake Study 21.12 using the RSQSim ERF to calculate the first regional probabilistic hazard map with fully-deterministic models. We computed approximately 26 million two-component seismograms and long-period (T≥2 sec) CyberShake-RSQSim hazard curves for 335 sites in the Southern California region. We will present results from this study, including comparisons with empirical ergodic ground motion models (GMMs) and with CyberShake Study 15.4, which used the UCERF2 ERF in the same region. When aggregated across all sites and sources, we find that the distribution of ground motions generated in Study 21.12 closely matches the distribution from ergodic GMMs. Additionally, hazard maps computed in Study 21.12 are qualitatively similar though show slightly lower than those from Study 15.4 at longer periods, with increased differences at shorter periods. This study demonstrates a practical approach for performing fully physics-based PSHA and provides an opportunity for detailed investigations of non-ergodicity in ground motions.

Key Words
probabilistic seismic hazard analysis, ground motion simulation, high performance computing

Callaghan, S., Milner, K. R., Goulet, C. A., Shaw, B. E., Maechling, P. J., Olsen, K. B., Graves, R. W., Vahi, K., Deelman, E., Jordan, T. H., & Ben-Zion, Y. (2022, 04). Non-ergodic PSHA using fully-deterministic physics-based models for Southern California. Oral Presentation at 2022 Seismological Society of America Annual Meeting.