Regional tsunami hazard assessment for communities of Bristol Bay and the Pribilof Islands, Alaska

We assess potential tsunami hazards for the communities of Dillingham, Nelson Lagoon, and Platinum in Bristol Bay, and St. Paul and St. George on the Pribilof Islands. The Bristol Bay communities have no high-resolution bathymetry or topography, therefore we conduct tsunami hazard assessments for these areas at the regional scale. The regional approach is a suitable, cost-effective approximation and replacement for high-resolution tsunami inundation maps. The Pribilof Islands communities do have the high-resolution baseline data necessary to produce high-resolution maps. The primary tsunami hazard considered for communities in this report originate from tsunamigenic earthquakes along the Alaska-Aleutian subduction zone and from underwater slope failures in the Bering Sea. Volcanic tsunamis are known to have generated waves up to 12 m in Bristol Bay about 3,500 years ago, but we do not model them in this study due to insufficient data on locations and volumes of these potential hazards. We numerically model tsunamis generated by eight different megathrust earthquakes and two landslide sources, analyze tsunami wave dynamics, and develop tsunami hazard maps. The tectonic tsunami scenarios that we examined simulate Mw 9.2 megathrust earthquakes with a slip distribution in the 5-35 km (3-22 mi) depth range along the Aleutian megathrust. The landslide tsunami scenarios include submarine mass failures on both sides of Umnak Plateau. The maximum assumed runup heights are 1.4 m (4.6 ft) for Dillingham, 3.5 m (11.5 ft) for Nelson Lagoon, and 4.9 m (16 ft) for Platinum. The maximum calculated tsunami runup in St. Paul is 16 m (52.5 ft); it is 5m (16 ft) in St. George, and 11 m (36 ft) near the St. George airport. Results presented here are intended to provide guidance to local emergency management agencies in initial tsunami inundation assessment, evacuation planning, and public education for mitigation of future tsunami hazards.The complete report and digital data are available from the DGGS website: http://doi.org/10.14509/30422.