High slab thermal gradient facilitates dehydration and megathrust ruptures in the Solomon Sea plate

Abstract

Devastating earthquakes tend to occur in the eastern portion of the Solomon Sea, while small–medium events are distributed along the entire margin. The process controlling megathrust ruptures along this convex slab remains enigmatic in terms of both its nature and the manner of its control. Through 3D modeling, we find a high temperature gradient on the obliquely oriented flank of the convex slab, providing new insights into the tectonics of curved trench subduction. The subduction slab temperature gradient reaches as high as > 10 °C/km, and the dehydration gradient exceeds 0.05 wt%/km, which is associated with the recurrence of M > 7.5 earthquakes in frequently ruptured megathrust faults. The subducted plate immediately beneath the Moho depth of the overriding plate, corresponding to the source region of the largest number of seismic events at a depth of 30 ∼ 40 km, exhibits peak values in both the slab thermal gradient and dehydration gradient, revealing previously unrecognized intrinsic correlations.