Distribution of Cumulative Tsunami Energy from Alaska-Aleutians to Western Canada

Abstract

Large tsunamis generated by earthquakes in the Aleutian Islands to Western Canada region have been recorded since 1788. The 1946 Aleutian tsunami, associated with a moderate earthquake (Ms 7.4), hit the Hawaiian Islands. The 1964 Gulf of Alaska tsunami was the largest (Imamura-Iida scale: m=4). The source areas of large tsunamis in 1957, 1964 and 1965 extend 600–900 km along the trench. These tsunamis were observed throughout the entire Pacific region. In this paper, the distribution of cumulative energy (square value of tsunami height, H², where H is the mean height per segment unit) for each 200-km segment along the Aleutian-Alaska trench is investigated for the recent (1900–2002) and historical (1788–1899) periods. For the total tsunamigenic energy, H², during the entire 215-year period, percentages of the energy received were 39% in Central Alaska, 32% in the Alaska Peninsula and 11% in the Central Aleutian Islands. During the recent period, the total energy in Central Alaska is nearly comparable with that of the Kamchatka and South Chilean regions. If the tsunami energy is accumulated with a mean rate since 1788, the expected value in Central Alaska is small in comparison with the observed value for the recent period, because of the 1964 event. Conversely, the expected values for the Central Alaska Peninsula (400-km length) and Yakutat (400-km length) regions are about twice as large as the observed values, suggesting high tsunami risks for those regions.