Probabilistic Tsunami Hazard Assessment (PTHA) for Crescent City, CA

Abstract

This report builds on and supercedes Phase I of a demonstration Probabilistic Tsunami Hazard Assessment (PTHA) study of Crescent City, California [23], which developed an improved methodology for PTHA and associated products that addressed only tsunami flooding depth. The study documented in this report was originally conceived as a follow-on that simply extended Phase I products to include additional tsunami parameters associated with tsunami flow in particular, current speed and momentum flux. As this study was underway, however, it was reviewed by the California Probabilistic Tsunami Hazard Analysis Work Group (CA PTHA WG) [25] that included experts on various PTHA issues, most notably the critical issue of seismic source specification. Subsequently, the CA PTHA WG review concluded that the CSZ sources used in the Phase I work was not adequately consistent with the 2014 Update to the National Seismic Hazard Maps (NSHM) [54]. Consequently, an improved suite of CSZ sources had to be developed that was more consistent with the NSHM, as discussed in Section 7.6. As a consequence, the entire set of inundation model simulations had to be repeated and new PTHA flow depth products were developed. The results presented here thus supercede the results presented in the Phase I report [23]. Both Phase I [23] and this study were funded by BakerAECOM and motivated by FEMA’s desire to explore methods to improve products of the FEMA Risk Mapping, Assessment, and Planning (Risk MAP) Program. Here we briefly summarize the goals, deliverables, technical challenges, additional work, primary results and conclusions, and recommendations of this study.