Title: Understanding the co-to-post-seismic transition through geodetic observations and slip imagery

Abstract:
Earthquake occurrence is mainly controlled by the spatio-temporal evolution of stresses in the Earth’s crust, primarily caused by the large-scale movement of tectonic plates. However, postseismic transient processes strongly contribute to stress redistribution after an earthquake and to the generation of catastrophic seismic sequences. It is thus critical to better understand them. Our project tackled this critical question by combining geodetic and seismological observations of the phenomena with numerical modelling. The novelty of the project, I will present, lay in the period over which the problem was addressed: the very early postseismic phase (minutes to days) for which few studies had been conducted. Indeed, the existence of suitable data for documenting this transition period between fast and slow slip was limited, and the methodologies to analyze these data and to provide accurate and robust slip imagery also needed to be improved or developed.
I will present a summary of the results we obtained based on our ability to accurately resolve deformation over a wide range of frequencies, amplitudes and spatial scales as well as to analyze and interpret the observations with a new approach to optimize the information contained in the surface observations or kinematic slip inversion from noisy surface ones. Our results on very early postseismic deformation allow for a better understanding of the complex spatial and temporal evolution of the deformation and hopefully by continuing to study this phase, a better assessment of fault slip over a seismic cycle, physical parameters controlling fault slip and ruptures and seismic hazard.