Tsunami Source Specification for Southeast Alaska with Focus on Inundation Mapping and Hazard Risk Assessment in Sitka
Abstract
The Alaska Earthquake Information Center (AEIC) conducts tsunami inundation mapping for coastal communities in Alaska. This activity provides local emergency officials with tsunami hazard assessment and mitigation tools. At-risk communities are spread along several segments of the Alaska-Aleutian Subduction Zone, with each segment having a unique seismic history and potential tsunami hazard. As a result, almost every community has a distinct set of potential tsunami sources that need to be considered in order to make a tsunami inundation map. Therefore, an important component of the inundation mapping effort is identification and specification of potential tsunami sources. We are creating tsunami inundation maps for Sitka, Alaska, in the scope of the National Tsunami Hazard Mitigation Program. Tsunami potential from tectonic and submarine landslide sources must be evaluated in this case for comprehensive mapping of areas at risk for inundation. The community of Sitka, the former capital of Russian Alaska, is located in Southeast Alaska, on the west coast of Baranof Island, facing the Pacific Ocean. In this area of southern Alaska, the subduction of the Pacific plate beneath the North America plate becomes a transform boundary that continues down the coast as the Fairweather - Queen Charlotte (FW-QC) transform fault system. The Sitka segment of the FW-QC fault system ruptured in large strike-slip earthquakes in 1927 (Ms7.1) and in 1972 (Ms7.6). We numerically model the extent of inundation in Sitka due to tsunami waves generated from earthquake and landslide sources. Tsunami scenarios include a repeat of the tsunami triggered by the 1964 Great Alaska earthquake, repeat of the tsunami triggered by the 2011 Tohoku earthquake, tsunami waves generated by a hypothetically extended 1964 rupture, a hypothetical Cascadia megathrust earthquake, and hypothetical earthquakes in the FW-QC fault system. Underwater landslide events off the continental shelf along the FW-QC fault zone are also considered as credible tsunamigenic scenarios. We perform simulations for each of the scenarios using AEIC's numerical model of tsunami propagation and runup, which was validated through a set of analytical benchmarks and tested against laboratory and field data. Results of numerical modeling combined with historical observations in the region will be delivered to local emergency management to be used in local tsunami hazard assessment, evacuation planning and public education.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMNH33A1646S
- Keywords:
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- 0545 COMPUTATIONAL GEOPHYSICS / Modeling;
- 3070 MARINE GEOLOGY AND GEOPHYSICS / Submarine landslides;
- 4564 OCEANOGRAPHY: PHYSICAL / Tsunamis and storm surges;
- 4304 NATURAL HAZARDS / Oceanic