Major (MW ≥ 7.0) Near-Trench Intraplate Compressional Faulting and the 25 March 2020 MW 7.5 Paramushir, Northern Kuril Islands Earthquake

Abstract:

Large compressional-faulting earthquakes located relatively deep in oceanic lithosphere entering subduction zones are primarily caused by plate bending stress, but their timing, depth extent and size can be influenced by temporally-varying shear stress on the plate boundary. The 25 March 2020 M_W 7.5 event in the Pacific plate seaward of Paramushir Island (northern Kuril Islands), is among the largest recorded events of this type. Its rupture extends along the southern portion of the 1952 Kamchatka M_W 9.0 rupture zone, a region that has somewhat lower interplate coupling than the megathrust fault along Kamchatka to the north. The 2020 event is considered in the context of the modest number of recorded major (M_W ≥ 7.0) near-trench intraplate compressional-faulting events. Particularly noteworthy are such events seaward of areas presumed to be in an advanced stage of their seismic cycle, including relatively shallow compressional events along the 1944 M_W 8.1 Tonankai rupture zone.