Breaking the plate – intraslab earthquakes

When tectonic plates converge, one plate is driven down beneath the other, and descends into the Earths interior. These downgoing tectonic plates are illuminated throughout this process by ongoing seismicity within the plate, and, although these earthquakes are typically smaller than the largest earthquakes that occur between plates, they can be devastating to the overlying areas.  However, unlike earthquakes occurring near the surface, these earthquake are much deeper (down to ~350 km), which makes studying them difficult.  We cannot access them or their source regions geologically, and modern geodetic techniques – which now underpin seismic hazard assessment in most settings – fail to resolve the deformation associated with these earthquakes, or with the slow building up of stress prior to their occurrence.  

The mechanism that allows such earthquakes to occur is also poorly understood – due to the great confining pressures at such depths, the mechanics of faulting in such earthquakes must be different from those at shallow depths.

This project will use seismological data to study these “intaslab” earthquakes at a range of sizes, mapping out their occurrence in high resolution.  I will integrate this will a set of advanced geodynamic models aimed at understanding what controls the location and size of such events, with the intention of producing a physics-based characterisation of the potential for any given portion of a subducted plate to produce a given size of earthquake, to inform seismic hazard assessment for the overlying regions.