Slip Distribution of the 1985 Valparaíso Earthquake Constrained with Seismic and Deformation Data

The 2017 Valparaiso seismic sequence calls attention to the potential seismic hazard for a megathrust earthquake in central Chile. Previous large historic earthquakes have been studied to improve our knowledge of the seismotectonic context in this region. In this work, we studied the slip distribution of the 3 March 1985 M w 8.0 Valparaiso earthquake. To model this event, we use a finite-fault model and a linear inversion scheme, incorporating data of near-field displacement, surface waves, and P, SH, and PP waves. The results show that the rupture propagated 90 km southward and 80 km northward from the hypocenter, with a total duration of 65 s. The slip is concentrated mainly on two patches of the rupture between 20 and 40 km depth. The patch of maximum slip is near the nucleation zone. The obtained slip distribution is in agreement with the asperities model, which describes the seismicity of central Chile. We confirm that the source did not break the upper part of the subduction interface and that a large tsunamigenic potential is still present in this region.