Source Properties and Resonance Characteristics of the Tsunami Generated by the 2021 M 8.2 Alaska Earthquake

Abstract

AbstractA tsunami was triggered in the North Pacific Ocean by the 2021 Alaska earthquake (M 8.2) on July 29. We studied the source properties and resonance characteristics of the tsunami event using observed records from offshore tsunameters and coastal tide gauges as well as numerical simulation. Spectral analyses were conducted on records at tsunameters and tide gauges. We reconstructed the tsunami source spectrum by calculating the ratio of tsunami spectra to the background spectra of these stations. Based on the source spectrum, we estimated the source size of the 2021 Alaska earthquake to be 332 km (length) 256 km (width), which was generally consistent with the source model proposed by the United States Geological Survey using seismological approaches. In addition, we also performed spectral analyses of the tsunami wavefield in a region of interest, including the Aleutian Islands and the Alaska Peninsula. Standing wave systems were found south of the Alaska Peninsula and the Aleutian Islands. The Aleutian Islands prevent the propagation of tsunami oscillations. Only a small portion of energy propagates through the archipelago from the main part of the Pacific Ocean to the Bering Sea.