Systematic biases in subduction zone hypocenters

Abstract

[1] Earthquake hypocenters from global datasets commonly have regional biases in their locations due to the use of a one-dimensional velocity model in their location. To analyze this effect, we group intermediate-depth earthquakes into forty-four 500-km-long sections of subduction zone. We relocate earthquakes in each group relative to one another and in a three-dimensional global velocity model. Hypocenters shift up to 25 km regionally when these effects are included; most earthquakes in circum-Pacific subduction zones are pulled toward the Pacific. Location uncertainties from the relative relocations are reduced to one-fifth of those from single-event locations; Wadati-Benioff zone thicknesses are reduced to two-thirds of their original thickness. These biases alter estimates of depth to slab beneath arc volcanoes up to 50 km, and alter measurements such as the volume of mantle wedge available for water storage or melt generation, and the size of the thrust zone on which large earthquakes can occur.