Updated tsunami inundation maps for Homer and Seldovia, Alaska

Abstract

We re-evaluate the potential tsunami hazard for the communities of Homer and Seldovia by numerically modeling the extent of inundation from tsunami waves generated by earthquakes and submarine landslides. Hypothetical worst-case scenarios are defined by analyzing the tsunami dynamics related to various plausible earthquake slip distributions along the Alaska-Aleutian megathrust. Potential tsunami sources include megathrust earthquakes in the Prince William Sound, Kenai Peninsula, and Kodiak Island regions. We consider scenarios similar to that of the 2011 Tohoku earthquake in Japan, with maximum slip located on a shallow portion of the plate interface close to the seafloor trench. We also consider local underwater slope failure scenarios for Kachemak Bay. The maximum predicted wave height from a tectonic tsunami is 10-12 m (33-40 ft) in Homer and 10-11 m (33-36 ft) in Seldovia, while the maximum landslide-generated tsunami may reach an elevation of up to 4 m (13 ft) on Homer Spit. In addition to Homer and Seldovia, we assessed the tsunami hazard for three small communities in Kachemak Bay: Seldovia Village, Jakolof Bay, and Kachemak Selo. Results presented here are intended to provide guidance to local emergency management agencies for tsunami inundation assessment, evacuation planning, and public education to mitigate future tsunami hazards. This report updates the previous assessment of tsunami hazard for Homer and Seldovia published in 2005. The complete report and digital data are available from the DGGS website: http://doi.org/10.14509/30095.