Strong motion simulation for mega-earthquakes in northern Chile from several potential rupture scenarios

Abstract:

Large earthquakes happened recently in Northern Chile: Tocopilla 2007 (Mw 7.7) and Iquique 2014 (Mw 8.1). Both events were well recorded by strong motion networks, provided valuable information to be used for forward predictions of ground motions records. In traditional finite-fault stochastic method one generic horizontal component of the synthetic accelerograms are obtained considering only incident vertical rays of S waves. The observed strong motion records show important differences among horizontal and vertical components. Then in order to generate 3 components of strong motion we improve this method to simulate the arrive to free surface of the P, SV and SH waves. We considered the incident and azimuth angles of direct seismic rays propagating for a layered velocity model including the free surface and energy partition. We validate our strong ground motion simulation by comparing the synthetic and observed data in a wide frequency range (0.1-20 Hz) for the Tocopilla (2007) and Iquique (2014) earthquakes. Finally, we use this method to propose the synthetic accelerograms for several potential rupture scenarios for mega-earthquakes in northern Chile, these scenarios were proposed considering coupling models and the historical earthquake records. The results show large PGA values near 1 g, for station located on hard rock. An important trade - off between the PGA and the proposed slip distribution was observed. The maximum slip distribution located in deeper seismogenic contact produce the large PGA in the nearest stations.