Unusual earthquakes in the Gulf of Alaska and fragmentation of the Pacific Plate

Abstract

Two recent Ms 7.6 strike‐slip earthquakes in the northern Gulf of Alaska ruptured a composite 250‐km‐long north‐striking zone in the Pacific plate. These shocks are attributed to a combination of enhanced tensional stress in the Pacific plate seaward of and following the great (Mw 9.2) Alaska earthquake of 1964, and compressional stress resulting from collision of the Yakutat terrane with North America. The occurrence of these shocks reflects fragmentation of the northeast corner of the Pacific plate, possibly the initial step in establishing a new plate boundary seaward of the current boundary.