Updated tsunami inundation maps of the Kodiak area, Alaska

Abstract

Staff from Alaska Earthquake Center, Geophysical Institute and Alaska Division of Geological & Geophysical Surveys evaluated potential potential tsunami hazard for the communities of Kodiak, Womens Bay, and for the U.S. Coast Guard base on Kodiak Island by numerically modeling the extent of inundation from tsunami waves generated by hypothetical earthquake sources. Worst-case hypothetical scenarios are defined by analyzing results of a sensitivity study of the tsunami dynamics related to various slip distributions along the Alaska-Aleutian megathrust. The worst-case scenarios for the Kodiak communities are thought to be the subduction zone earthquakes offshore Kodiak Island with their greatest slip at 5-35 km (3.1-22 mi) depth. We also consider earthquakes as large as the 2011 Tohoku earthquake in Japan with the greatest slip located close to the trench area. The results show that the maximum predicted flow depth in downtown Kodiak could reach 13 m (42.6 ft), and the currents in Kodiak's Inner Harbor could be as strong as 3.7 m/sec (7.2 knots). The dangerous wave activity is expected to last for at least 10 hours after the earthquake. Results presented here are intended to provide guidance to local emergency management agencies in tsunami inundation assessment, evacuation planning, and public education to mitigate future tsunami hazards. This report updates the previously published assessment of tsunami hazard for the Kodiak Island communities. Users can access the complete report and digital data from the DGGS website: http://doi.org/10.14509/29740.