Ground-Motion Evaluation of Moderate and Large Interface Earthquakes along the Chilean Subduction Zone

Abstract

ABSTRACTStrong-motion observations of recent interface earthquakes along the Chilean subduction zone are evaluated with two ground-motion models (GMM). One GMM was developed with Chilean data and the other with global data. The GMM developed with local Chilean data is found to have an overall better prediction performance than the GMM developed using a global data set. Using residual analysis with the Chilean GMM as reference model due to its better performance, clear indications of an increase of short-period radiation for deeper earthquakes in north and central Chile were found, which may be related to frictional features on the interface such as interseismic coupling, as found previously for other regions, such as Japan. Also, the Iquique earthquake, which featured a clear precursory slow-slip event, exhibits mostly negative between-event residuals at short periods for earthquakes before and after the mainshock, indicating predominantly weaker short-period radiation. However, this trend is not observed in the aftershock sequence of the Illapel earthquake, which did not feature a significant slow-slip event nor precursory seismicity in its rupture area. Finally, a poor predictive performance was found for the Chilean GMM in southern Chile, overpredicting most of the observations. Based on these results, it is proposed that future local GMMs should include corrections for depth, regional effects and include earthquakes from southern Chile, as new data are becoming available in this region.