Variations in dv / v Susceptibility to Earthquake Shaking Along the Alaska Subduction Zone

Abstract

Earthquake‐triggered decreases in relative seismic velocity ( dv / v ) of the crust have been reported for many events, but regional variations in dv / v susceptibility to shaking are not well understood. Here, 14 Alaskan earthquakes with Mw 6.8–8.2 are consistently analyzed with single‐station coda‐wave interferometry. For peak ground velocities (PGV) >1 cm/s, significant dv/v drops are found for ∼40% of seismometers, with a moderate linear correlation coefficient of −0.3 between dv / v and PGV. Sites in the highest susceptibility decile, indicated by the largest dv / v drops per unit PGV, are all located near active volcanoes: Akutan, Makushin, Shishaldin, Pavlof, Katmai, and Augustine. Some Cook Inlet basin sites are among the largest decile of dv / v drops but have lower susceptibility due to amplified PGV. Frequency‐dependence of dv / v indicates concentration of velocity changes at <500 m depth, consistent with hydrothermal systems and weakly consolidated volcanic rocks influencing heterogeneous and high susceptibility near volcanoes.