A Bayesian Framework for Inferring Probabilistic Date of Last Event Between Sites with Paleoseismic Data

Morgan T. Page

Submitted August 30, 2026, SCEC Contribution #15280, 2026 SCEC Annual Meeting Poster #150

Modern seismic hazard models such as the Uniform California Earthquake Rupture Forecast, version 3 (UCERF3) and the 2023 National Seismic Hazard Model (NSHM23) represent fault-based earthquake sources on complex, interconnected fault networks. Some fault sections in these models have paleoseismic date-of-last-event (DOLE) data that can be used in elastic-rebound calculations to modify earthquake rupture probabilities. However, DOLE data are only available for a subset of fault sections, raising the question of how elastic-rebound calculations should be applied at other fault sections that may or may not have participated in the same most recent earthquake as a section or set of sections with paleoseismic data.

We present a Bayesian framework for probabilistically inferring the DOLEs throughout a fault network. Given the long-term, time-independent rupture rates of an underlying model (e.g., UCERF3 or NSHM23) and paleoseismic DOLE probability density functions at trench sites, we calculate the posterior probability that a given fault section last co-ruptured with any specified subset of fault sections with paleoseismic data. We currently assume rupture sources are independent Poisson processes, although any point-process survival function could be used. The resulting posterior co-rupture probabilities are used to construct DOLE probability distributions throughout the fault system. Furthermore, this method can be used to update DOLE distributions at the paleoseismic sites themselves, since nearby paleoseismic sites provide information about a site’s most recent event if there is a possibility of co-rupture.

Key Words
paleoseismic data, earthquake rupture forecast, Bayesian inference

Citation
Page, M. T. (2026, 08). A Bayesian Framework for Inferring Probabilistic Date of Last Event Between Sites with Paleoseismic Data. Poster Presentation at 2026 SCEC Annual Meeting.

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