Asperity Distribution of Alaskan-Aleutian Earthquakes: Implications for Seismic and Tsunami Hazards

The slip distributions of five great Alaskan-Aleutian earthquakes of the 20th century are determined by inversion of tsunami waveforms recorded on tide gauges. These earthquakes are the 1938 Alaskan, 1946 Aleutian, 1957 Aleutian, 1964 Prince William Sound, and 1965 Rat Islands earthquakes. These earthquakes have in general not been well-studied due to a lack of seismic data. The tsunami waveform inversion gives previously unknown information about the earthquake source. The results of tsunami inversion are compared to seismic inversion results where they exist and show high correlation to the seismic results. The slip distributions show highly variable slip occurred in each earthquake. The areas of highest slip, asperities, may be the locations of future high slip in great earthquakes. This information is vital because asperities control the location of strong ground motion and the run-up height of tsunamis. These results can be used to make predictions concerning future large earthquakes.