Physical models for the California transform fault system rupture hiatus and their conditional probability consequences

Glenn P. Biasi, & Katherine M. Scharer

Submitted September 11, 2022, SCEC Contribution #12178, 2022 SCEC Annual Meeting Poster #199

The paleoseismic records included in UCERF3 on main transform faults of California have an unusual quality of lacking paleoseismic surface rupturing events in over 100 years. The “transform fault system” (TFS) includes most of the highest slip faults in the state. Recent analyses put the collective probability of this hiatus among collections of independent sites at between 0.3 and 3.5%. With so small a probability that the hiatus is a statistical fluke, alternative explanations must be considered. We consider possible causes of correlation among the records, and potential consequences for conditional probability estimates of future rupture. Three candidate explanations have been suggested. Noting the elevated activity of the eastern California Shear Zone (Joshua Tree, Landers, Hector Mine, Landers, Owens Valley, etc.), some suggest an alternation is taking place that leads to a decrease in activity on the western side of the system. Alternatively, mechanical models of fault rupture suggest that where a system has lithospheric strength heterogeneities, that the strong portion can, in effect, organize fault activity nearby. Motion forced on the structure could influence timing of ruptures over a length scale similar to that of the heterogeneity. Finally, correlation among paleoseismic records could occur if coupling of the lithosphere in plate-scale viscous structure leads TFS faults to a slip pulse behavior, such as has been noted in the successive east-to-west ruptures in the 20th century on the North Anatolian Fault in Turkey. Evidence in California has some qualities of a slip pulse.

If some basis for correlation exists between paleoseismic sites, this would have practical implications for seismic hazard estimation. We review candidate correlation models, and consider their conditional probability consequences using paleoseismic records from California.

Key Words
Paleoseismic earthquake recurrence, conditional probability

Biasi, G. P., & Scharer, K. M. (2022, 09). Physical models for the California transform fault system rupture hiatus and their conditional probability consequences. Poster Presentation at 2022 SCEC Annual Meeting.

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