Developing Inundation Maps for Southern California

Abstract

There is little question that offshore seismic sources exist and could trigger tsunamis directly or through coseismic submarine offshore landslide or slump generation. While some earlier 19th century reports are subject to interpretation, more than 20 tsunami events have impacted the State of California in the past two centuries. California presents nontrivial challenges for assessing tsunami hazards, including a short historic record and the possibility of nearshore events with less than 20 min propagation times to the target coastlines. Here we present a brief history of earlier efforts to assess tsunami hazards in the State, and our methodology for developing the first generation inundation maps. Our results are based on worst case scenario events and suggest inundation heights up to 13 m. These maps are only to be used for emergency preparedness and evacuation planning. The present data record does not allow a more detailed quantitative assessment of tsunami risk; however, given the intense coastal land use and recreational activities along the coast, even a small hazard may pose high risk.