Ucerf 3 implementation for a site-specific probabilistic seismic hazard analysis in southern california

The UCERF3 procedure represents a departure from the traditional approach of developing a seismic source model and then computing probabilities of exceedance, in that it begins with a set of seismic source characterizations with full variability and then performs a state-wide inversion to best fit observed data. This allows the UCERF3 model to incorporate multi-fault rupture scenarios while honoring observed seismicity, paleoseismic, geologic, and geodetic data; however, the computationally intensive inversion is impractical to reproduce and refine for sitespecific applications. We present a methodology for implementing the UCERF3 seismic source model for site-specific PSHA. The proposed methodology allows for the incorporation of 1) local faults not included in the more regional UCERF3 model, 2) added epistemic branches in the UCERF3 fault characterizations based on local site-specific data, and 3) incorporation of near-source directivity effects in the PSHA. An application example is presented for a sitespecific PSHA for the Sanitation Districts of Los Angeles County in Southern California. Additionally, our methodology has been used and reviewed on recent projects, including the Lawrence Livermore National Laboratory and Sisk Dam in California. 1 Fugro, 1777 Botelho Dr., Suite 262, Walnut Creek, CA 94596; (email: afernandez@fugro.com) 2 Fugro, 1726 Cole Blvd., Suite 230, Lakewood, CO 80401; (email: j.altekruse@fugro.com) 3 LaForge Geoconsulting, 16682 W 56th Dr, Golden, CO 80403; (email: laforgegeoconsulting@gmail.com) 4 Ostenaa Geologic LLC, 25 Grays Peak Tr., Dillon, CO 80435; (email: deano3geo@gmail.com) 5 Fugro, 1777 Botelho Dr., Suite 262, Walnut Creek, CA 94596; (email: oelmenchawi@fugro.com) 6 Fugro, 1777 Botelho Dr., Suite 262, Walnut Creek, CA 94596; (email: ttravasarou@fugro.com) Fernandez, A., Altekruse, J., LaForge, R., Ostenaa, D., El Menchawi, O., and Travasarou, T. (2018). UCERF3 Implementation for a Site-Specific Probabilistic Seismic Hazard Analysis in Southern California. Proceedings of the 11th National Conference in Earthquake Engineering, Earthquake Engineering Research Institute, Los Angeles, CA. Eleventh U.S. National Conference on Earthquake Engineering Integrating Science, Engineering & Policy