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Bayesian Assimilation of Multicycle Earthquake Simulations into Probabilistic Forecasting Models.

Luis Vazquez, & Thomas H. Jordan

Submitted September 11, 2022, SCEC Contribution #12365, 2022 SCEC Annual Meeting Poster #207

A general problem in earthquake forecasting is how to assimilate deterministic physical simulations into probabilistic forecasting models. Here we focus on recalibrating the time-independent Uniform California Earthquake Rupture Forecast Version 3 (UCERF3-TI) of Field et al. (2014) against long earthquake catalogs (~1 million years) generated by the multi-cycle Rate-State Quake Simulator (RSQSim) of Dieterich & Richards-Dinger (2010). We map RSQSim ruptures from the Shaw et al. (2018) catalog onto equivalent UCERF3 ruptures by maximizing the mapping efficiency while preserving the seismic moment. We assume the sequence of equivalent UCERF3 ruptures is Poisson distributed, i.e., each rupture occurs at a time-independent rate, our knowledge of which is uncertain. We use the full UCERF3 logic tree to construct a joint prior distribution of rupture rates, which we represent by independent Gamma distributions. Updating the UCERF3 gamma priors with the empirical RSQSim Poissonian rate yields Gamma posterior distributions that can be calculated analytically. Our results show that participation rates are decreased in the northern section of the San Andreas Fault System (SAF) with respect to the UCERF3 model, which we attribute to the slip rate difference between RSQSim and UCERF3. Furthermore, our posterior model results in substantial lower rates in the Coachella, San Gorgonio, and San Bernardino SAF sections, reflecting the fact that RSQSim does not propagate ruptures through the San Gorgonio knot. We also briefly address the more challenging problem of constructing time-dependent forecasts that have been conditioned on knowledge of the previous rupture history over time intervals of the last 100 years or so.

Vazquez, L., & Jordan, T. H. (2022, 09). Bayesian Assimilation of Multicycle Earthquake Simulations into Probabilistic Forecasting Models.. Poster Presentation at 2022 SCEC Annual Meeting.

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