| Summary: | The 17 July 2017 Komandorsky Islands M_W 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. © 2017 American Geophysical Union. Received 23 OCT 2017; Accepted 1 DEC 2017; Accepted article online 8 DEC 2017; Published online 23 DEC 2017. The IRIS DMS data center (http://www.iris.edu/hq/) was used to access the seismic data from Global Seismic Network and Federation of Digital Seismic Network stations. Tsunami waveform data were obtained from the NOAA National Data Buoy Center (http://www.ndbc.noaa.gov/). Our GPS solutions are available from M. Kogan and J. Freymueller upon request. Raw data for all sites on the Alaska side are available from the UNAVCO archive, raw data for PETS are available from all IGS data centers, and raw data from BRNG are available from the Geophysical Survey of the Russian Academy of Sciences data center. We thank Kevin Furlong for discussions of the regional tectonics. Keith Koper shared his back projections of North American P waves, and Gavin Hayes shared his early finite-fault models with us. We appreciate comments and suggestions from two anonymous reviewers. This work was supported by National Science Foundation grant EAR1245717 to Thorne Lay. Published - ...
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