Bayesian Assimilation of Deterministic Multicycle Earthquake Simulations into Probabilistic Rupture Forecasts

Luis Vazquez, & Thomas H. Jordan

Published September 10, 2023, SCEC Contribution #12924, 2023 SCEC Annual Meeting Poster #153

We develop methods for assimilating the information from deterministic multi-cycle earthquake simulators into probabilistic rupture forecasts. We utilize long earthquake catalogs generated by the multi-cycle Rate-State Quake Simulator (RSQSim) of Dieterich & Richards-Dinger (2010) to recalibrate the rates of large earthquakes (M≥7) prescribed by the time-independent Uniform California Earthquake Rupture Forecast Version 3 (UCERF3-TI) of Field et al. (2014). Shaw et al. (2018) generated a million-year earthquake catalog from an RSQSim California simulator with UCERF3 fault geometries and slip rates and found that the expected shaking hazard derived from the synthetic catalog showed good agreement the published UCERF3 hazard maps. In this study, we take this head-to-head comparison to the more granular level of individual faults and ruptures, formally testing the onological null hypothesis (ONH) that the empirical RSQSim rupture counts from the Shaw et al. (2018) million-year catalog are statistically consistent with the UCERF3 rate distributions, given the epistemic uncertainties. Setting up this comparison requires that we associate each RSQSim rupture realization with a unique, but geometrically much simpler, UCERF3 rupture. We optimize the association algorithm by maximizing the mapping efficiency while preserving seismic moment. We use the full UCERF3 logic tree to construct a joint prior distribution of rupture rates, which we represent as a set of independent Gamma distributions. Updating the UCERF3 priors with the empirical RSQSim rates yields Gamma posterior distributions that can be calculated analytically. Differences in earthquake participation rates after data assimilation can be associated with differences in slip rates, fault interconnectivity, and rupture complexity.

Citation
Vazquez, L., & Jordan, T. H. (2023, 09). Bayesian Assimilation of Deterministic Multicycle Earthquake Simulations into Probabilistic Rupture Forecasts. Poster Presentation at 2023 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Forecasting and Predictability (EFP)