SCEC2021 Plenary Talk, Earthquake Geology

Revisiting geologic fault slip rates - and their uncertainty - across southern California

Veronica B. Prush, & Michael E. Oskin

Oral Presentation

2021 SCEC Annual Meeting, SCEC Contribution #11137
Models of earthquake hazard rely on geologic fault slip rates to forecast future activity. With the increasing complexity of earthquake forecasting, it's crucial to apply consistent uncertainty models to the input geologic data. To date, the treatment of uncertainty in measurements of fault displacement and offset-feature age has not been consistent across slip rate studies. This results from the unique geologic history at each site and the individual choices of the publishing authors. Recent advances in surface-exposure dating techniques also impact the interpretation of many slip rate sites. We apply new production rate estimates and a mechanistic model for surface clast-age populations to sites in southern California. Offset probability distributions are interpreted from information reported by publishing authors. We assess the impact of updated slip rates using both the median age and the overlap of uncertainty with the published rates. Our study highlights the importance of the consistent application of uncertainty models, and future work should expand to improve uncertainty models for other geochronometric techniques. Additional improvements may be gained through reassessment of existing sites with additional geochronology samples and analysis of now widely available lidar data. This should yield substantially improved uncertainty constraints for slip rates, particularly in older studies where high-resolution topographic datasets were not available at the time of publication.