Re-examination of the Potential for Great Earthquakes along the Aleutian Island Arc with Implications for Tsunamis in Hawaii

I have focused on estimating the largest tsunamigenic earthquakes in the Aleutian Islands that may affect Hawaii. I reviewed the seismological and tsunami literature on the great earthquakes along the Aleutian-Alaska arc for events since the dawn of instrumental seismology and for historical studies prior to 1900 and summarized the earthquake source mechanisms, fault rupture zones, and seismic moment release characterizing the earthquakes for the principal fault segments demarcating the arc. Average cumulative fault displacements were derived for the segments assuming a common rigidity and then compared with average displacements observed for the two largest megathrust earthquakes recorded, the 1964 Alaska and 1960 Chile earthquakes. Scaling average fault displacement on each segment to the levels observed for the 1964 Alaska and 1960 Chile earthquakes provides a measure of the largest credible earthquakes along the Aleutians. Several segments of the Aleutian arc have the potential for magnitude Mw 9 events. In the region between the ruptures of the 1946 and 1957 great tsunamigenic earthquakes in the Aleutians, there is a ∼700 km extent in the east Aleutian Islands without signifi-cant fault displacement in more than a century, which has the potential for an Mw 9.0-9.4 earthquake with a concomitant large tsunami. A tsunami forecast model for an Mw 9.25 earthquake in this region shows inundations in Hawaii exceeding historic run-ups. Given the proximity of this potential earthquake to the largest tsunamigenic sources that have impacted the Hawaiian Islands, further tsunami modeling and review are warranted for this event, as well as for other potential Mw 9 earthquakes in the Aleutians. To augment models of the historical earthquake data from the Aleutians, tsunami inundations maps in Hawaii and elsewhere should consider these potentially larger tsunamigenic events. This potential for large tsunamigenic events affecting the Hawaiian Islands with less than five hours' warning underscores the necessity for a robust tsunami warning system and the need for additional tsunami sensors between the Aleutians and Hawaii (see Figure 1).