Joint Inversion of High-Rate GPS and Teleseismic Observations for Rupture Process of the 23 June 2014 (M_w 7.9) Rat Islands Archipelago, Alaska, Intermediate Depth Earthquake

Abstract

On 23 June 2014, a large (M_W 7.9) earthquake ruptured within the subducting Pacific plate ~100 km below the Rat Islands archipelago, Alaska. The focal mechanism indicates two possible rupture orientations: on a shallowly dipping fault plane striking perpendicular to the trench, possibly related to curvature of the underthrust slab or; on a steeply dipping fault plane striking parallel to the trench, possibly associated with a slab detachment process. Joint inversion of teleseismic body waves and regional high‐rate (1Hz) GPS recordings indicate a slip zone spanning 50 km × 30 km with a maximum slip of ~11 m on the shallowly dipping plane, or a more distributed slip pattern extending upward to ~70 km, with maximum slip of ~14 m on the steeply dipping plane. The finite‐fault models and aftershocks do not indicate a preferred fault plane. This type of intermediate‐depth intraslab faulting can be very damaging for populated regions above subduction zones such as Japan, Taiwan, Chile, Peru, and Indonesia.