Alaska Megathrust Source Characterization for Tsunami Hazard

Date: 4/24/2019

Time: 11:30 AM

Room: Pike

The Alaska subduction zone is the most significant source of tsunami hazard for Alaska, Hawai’i and most of California. Due to the inaccessibility of large swaths of the Aleutians through most of the year, relatively little is known about the history of large megathrust events, especially west of Kodiak. Building an event recurrence model for probabilistic seismic and tsunami hazard analysis is therefore quite challenging and inevitably includes a large epistemic uncertainty. For tsunami hazard, the challenge is even greater since details in the maximum extent and distribution of megathrust events will have a sizeable impact on the final hazard results.

For the update of the California tsunami hazard maps as well as the new ASCE 7-16 chapter on tsunami loads and effects, we adopted a simple recurrence model that consists of single and multi-segment ruptures based on the Jacobs and Nishenko model. These were largely constrained by paleoseismic data, recent event history and a general model of subduction zone tectonics.

Since that effort was concluded, the USGS Powell Center has funded a Working Group “Tsunami Source Standardization for Hazards Mitigation in the United States” tasked with the development of models those sources that contribute to the tsunami hazard in the United States. One of the first workshops was entirely devoted to the Alaska subduction zone and benefited from the expertise of a wide array of scientists from different disciplines including seismology, geodesy, geology and coastal engineering. Although this model is being developed for tsunami hazard analysis, it should also be easily adaptable for use in the next generation of seismic hazard model for Alaska.

In this presentation, we will discuss the evolution of the earlier USGS source model through the ASCE 7-16 model to the comprehensive Powell Center model and discuss the major differences, both in approach, constraints, uncertainties and potential impact on tsunami hazard studies.

Presenting Author: Hong Kie Thio

Authors