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Testing earthquake recurrence models with paleoseismic time series

Wing Yee Winnie Lau, Michael E. Oskin, & Bruce E. Shaw

Submitted September 11, 2022, SCEC Contribution #12035, 2022 SCEC Annual Meeting Poster #198

We directly test earthquake recurrence models using long paleoseismic time series from California, augmented by long time series available from other areas of continental strike-slip faulting (e.g. China, Israel, and New Zealand). Testing how statistical models are applied to paleoseismic data has the potential to transform how the community approaches seismic hazards. Paleoseismic time series are sampled from the full event-age probability distributions, as constrained from bounding layer ages and, if applicable, sedimentation rate information. Typically, the extent of each rupture and its similarity to other events are unknown. We objectively compare statistical model performance using maximum likelihood estimation. Using our preliminary datasets, we find that long earthquake time series (here defined as 9 or more events) provide sufficient information to discriminate between Brownian Passage Time (BPT) and Weibull recurrence models for these ground-failure events, as well as ruling out other commonly assumed models such as a normal (Gaussian) distribution or exponential (Poisson) distribution. We find that the Brownian passage-time model, formulated as perturbations added to steady tectonic loading, systematically underpredicts the young tail of earthquake recurrence. We find better fits for the majority of paleoseismic data sets using a Weibull distribution. The Weibull model may be envisioned as arising from an ensemble of many possible failure points (earthquake nucleation sites) along a given length of the fault, at each of which the hazard is growing over time. Once initiated, a rupture grows and propagates through the point of observation at a paleoseismic trench. Earthquake distributions vary widely along the length of the 1857 Fort Tejon earthquake rupture and suggest that interactions with the Garlock Fault and the San Jacinto Fault affect the time to failure on the San Andreas fault. We also present forthcoming comparisons of paleoseismic event recurrence in California to results from the RSQsim earthquake simulator.

Key Words
paleoseismicity, paleoearthquakes, earthquake recurrence intervals, statistical fits

Lau, W., Oskin, M. E., & Shaw, B. E. (2022, 09). Testing earthquake recurrence models with paleoseismic time series. Poster Presentation at 2022 SCEC Annual Meeting.

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