Earthquake Recurrence Model for the Colombia-Ecuador Subduction Zone Constrained from Seismic and Geodetic Data, Implication for PSHA

摘要

Probabilistic seismic hazard assessment relies on long-term earthquake forecasts and ground-motion models. Our aim is to improve earthquake forecasts by including information derived from geodetic measurements, with an application to the Colombia-Ecuador megathrust. The annual rate of moment deficit accumulation at the interface is quantified from geodetically based interseismic coupling models. We look for Gutenberg-Richter recurrence models that match both past seismicity rates and the geodetic moment deficit rate, by adjusting the maximum magnitude. We explore the uncertainties on the seismic rates (a- and b-values, shape close to M-max) and on the geodetic moment deficit rate to be released seismically. A distribution for the maximum magnitudeMmax bounding a series of earthquake recurrence models is obtained for the Colombia-Ecuador megathrust. Models associated with Mmax values compatible with the extension of the interface segment are selected. We show that the uncertainties mostly influencing the moment-balanced recurrence model are the fraction of geodetic moment released through aseismic processes and the form of the Gutenberg-Richter model close to M-max. We combine the computed moment-balanced recurrence models with a ground-motion model, to obtain a series of uniform hazard spectra representative of uncertainties at one site on the coast. Considering the recent availability of a massive quantity of geodetic data, our approach could be used in other well-instrumented regions of the world.