An Alaska-Aleutian subduction zone interface earthquake recurrence model from geology and geodesy

Abstract

We present an earthquake recurrence model for the subduction interface of the Alaska–Aleutian subduction zone from geodetic and paleoseismic data. To capture variations in rupture behavior along strike, we define fault sections based on geodetic coupling, prehistoric earthquake and tsunami recurrence, historical ruptures, and geologic and geophysical structure. In the 1964 M w 9.2 rupture area, which spans four fault sections, recurrence rates for section participation in presumed great ( M w 8.5+) events vary from ∼600 years (Prince William Sound section) to ∼380 years (Kodiak section), geodetic character varies substantially along strike, and geologic evidence indicates that rupture patches vary in space and time. Westward along the Semidi section, the recurrence of large, tsunamigenic ruptures is more frequent (∼220 years) based on geologic and geodetic data than previously assumed. The seismic potential of the Shumagin section, an area of low coupling, remains enigmatic despite a large ( M w 7.8) rupture in 2020. Prehistoric tsunami data indicate that inundation recurrence in the Fox Islands is ∼210 years. Paleoseismic data are lacking west of the Fox Islands, so rupture rates along the western 1900 km of the subduction interface to Komandorski are inferred from geodetic constraints.