The 1 May 2017 British Columbia‐Alaska Earthquake Doublet and Implication for Complexity Near Southern End of Denali Fault System

Abstract

AbstractOn 1 May 2017, two MW6.2 earthquakes occurred near the border of northwestern British Columbia and Alaska separated by about 2 hr in time. Despite their close distance (~10 km), the two events have different focal mechanisms, with the first featuring a reverse focal mechanism and the second strike slip. Both focal plane solutions are inconsistent with the nearby southeastern Denali fault system. To resolve their ruptured fault planes, we invert for the earthquake point source parameters and analyze rupture directivity via regional and teleseismic waveforms. We also model the near‐field GPS data and relocate the aftershocks to determine the fault planes. The results indicate that the first event ruptured updip along a steep SW‐dipping fault and the second event ruptured to the ESE along a left‐lateral fault. We infer that the earthquake doublet was related to the regional stress field and slip on the active Duke River fault. The involved faults are associated with transpression caused by the oblique collision of the Yakutat block.