ABSTRACT

On 1900‐10‐09 a large (Mw 7.6–8.0) earthquake occurred in the Gulf of Alaska and strongly shook the port town of Kodiak. Some damage occurred to buildings and the wharf, and dozens of aftershocks were felt over the next several hours and days. Global seismic stations recorded the earthquake from as close as Victoria, western Canada, to as far as Capetown, South Africa. Here we collect an expanded set of felt reports and instrumentally recorded arrival times to estimate an epicentral area centered at (151.0°, 57.4°), north of the subduction plate boundary, and about 95 km southeast of Kodiak. We propose three possible source regions for the 1900 earthquake: (1) the subduction interface (which hosted the 1964 Mw 9.2 earthquake), (2) subducted oceanic lithosphere, hosting a strike‐slip earthquake, or (3) active faults within the accretionary wedge. Lack of evidence of any significant tsunami provides an important constraint for future modeling to discriminate among the three source regions. The earthquake occurrence adds to a complex tectonic setting offshore of Kodiak Island. The incoming deforming Pacific plate meets an actively faulted overlying accretionary wedge, with the subduction interface between the plate and the wedge being capable of Mw>9 earthquakes.

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