Evidence of Wadati-Benioff zone triggering following the M w 7.9 Little Sitkin, Alaska intermediate depth earthquake of 23 June 2014

Abstract

The 23 June 2014 Mw=7.9 earthquake that struck the Rat Islands region of Alaska was a rare intermediate-depth event followed by a vigorous aftershock sequence. The earthquake's location within a regional network has allowed us to study it in rich detail. Double-difference relocations of aftershocks and static stress modeling reveal some intriguing features; most aftershocks are not located on the main shock rupture plane, but are concentrated in the adjacent Wadati-Benioff zone in areas of increased stress. Further, a secondary plane of seismicity aligns well with a moderately dipping nodal plane reported by the Global Centroid Moment Tensor Project, and the separation of these locations and the main shock hypocenter from the slab indicates that the main shock ruptured into the oceanic mantle.