Slab dehydration and earthquake distribution beneath southwestern and central Japan based on three-dimensional thermal modeling

Abstract

We developed a 3-D thermal convection model to estimate the thermal regime, water content distribution, and slab dehydration beneath southwestern and central Japan, where deep tectonic tremors and short-term slow slip events (S-SSEs) are frequently observed on the plate interface extending from the western Shikoku to the Tokai district. The results showed that the pressure-temperature (P-T) conditions for the S-SSEs, deep tectonic tremors, and regular earthquakes indicate that they probably originated from slab dehydration in association with subduction, resulting in a phase transformation from prehnite-actinolite/lawsonite blueschist to amphibolite with a large thermal gradient. Slab dehydration and the thermal gradient in the dip direction are considered key factors for controlling the seismogenesis of slow and regular earthquakes in the Philippine Sea plate beneath southwestern and central Japan, although the deep tectonic tremors are more complicated because they are likely favored by a comparatively low temperature gradient in southwestern Japan.