Abstract

Intraslab earthquakes – those earthquakes occurring at intermediate depths within oceanic lithosphere as it is subducted into the Earths interior – pose a range of geophysical problems.  Starting from the comparative rarity of such earthquakes, and the difficulty we have in accurately observing and monitoring them, these problems extend to major unknowns around the physical mechanism that allows rupture to occur at such pressures and temperatures. A range of plausible hypotheses remain, from dehydration embrittlement and stress transfer, to shear heating, with observations as yet unable to isolate the causative mechanism.  As a result of this, the hazard these earthquakes can pose to arc regions in subduction zones remains poorly understood, and poorly characterised. In this talk, I will summarise a range of recent projects, firstly aimed at improving how we observe, located and characterise intraslab seismicity.  This will cover both the use of modern global seismology and, where possible, surface geodesy.  I will then build on this, discussing ways in which we can use the increasingly rich range of observations to understand the properties of this class of seismicity, and the rheological and mechanical conditions required in order to facilitate brittle, seismogenic failure at slabs in the upper mantle.