SEISMogenic behavIour of COntinental Subduction: insights from rheology and petrophysics

forthcoming

Understanding the processes controlling the seismogenic behaviour (seismic vs. aseismic) of deformation in convergent margins is one of the fundamental unresolved scientific and societal challenges. Despite the elevated seismic hazard posed by damaging earthquakes in populated areas where continental subduction occurs (e.g. Taiwan 1999 Chi Chi MW = 7.6; Nepal 2015 Gorkha MW = 7.8), little is known about the parameters controlling the seismogenic behaviour of the subducted quartz-rich continental crust. Current geophysical and experimental observations suggest a tight interplay between the presence of, or lack thereof, fluids and the rheology of subducted continental crust. In the SEISMI-COS project I will quantify how rheology and petrophysics controlled the seismogenic behaviour of fossil analogues of deformation zones developed during continental subduction. I will investigate the deformation structures developed at progressively larger depths during Alpine subduction, now exposed at the surface in different tectonic units of Northern Corsica. By integrating field structural and digital analyses, cutting-edge microstructural analyses (EBSD, m-CT), with laboratory measurement of petrophysical properties (lab gas-permeameter) I will quantify the microstructural processes and petrophysical properties characterizing the deformation behaviour of the continental crust at progressively larger subduction depths. This will allow me to provide the input parameters for rheological and numerical models, through which I will investigate the how rheology and petrophysics interact to control the deformation mode, and to test the inferences made from field and microstructural investigations on the seismogenic behaviour. These results will bring us groundbreaking insights on the parameters and processes controlling seismogenesis in continental subduction zones.