Rupture Along 400 km of the Bering Fracture Zone in the Komandorsky Islands Earthquake (MW 7.8) of 17 July 2017

The 17 July 2017 Komandorsky Islands <fi>M</fi>_<fi>W</fi> 7.8 earthquake involved arc-parallel right-lateral patchy strike-slip faulting along 400 km of the Bering Fracture Zone (BFZ) in the westernmost Aleutian Islands back arc. The large size of the earthquake indicates that the BFZ serves regionally as the primary plate boundary extending from the Near Islands to Kamchatka, with the fore-arc Komandorsky Sliver translating rapidly parallel to the Aleutian Trench. The slip distribution is determined by analysis of seismic, tsunami, and geodetic observations. Fault displacements of 4 to 8.5 m, mostly in the upper 15 km, but with localized extension to 20 to 30 km depth along a 100 km long segment of the BFZ, are comparable to the possible slip deficit since the last major earthquakes in this region in 1849 and 1858, given an estimated 5.1 cm/yr rate between the Komandorsky Sliver and the Bering Plate.