Stochastic strong-ground motion simulation in the Santiago metropolitan region considering an Mw 7.8 intraplate intermediate-depth earthquake

Large intraplate intermediate-depth (IID) events are the most destructive to Chilean structures and they occurred throughout the country. Cities located above the hypocenters of these large earthquakes have been completely destroyed. In recent years, only small-and moderate-magnitude IID events have been reported below Santiago, the most populated Chilean city; however, the occurrence of large-magnitude IID events cannot be ruled out. In this study, we investigated the strong-ground motion generated by large-magnitude earthquakes occurring below the Santiago metropolitan region. We used a stochastic methodology to simulate synthetic records, considering IID events of magnitude Mw 7.8. To validate this method, we simulated intermediate-depth events of magnitudes Mw similar to 5-6 that occurred near Santiago. We further calibrate our results by reproducing the strong-ground motion data recorded during the 2005 Tarapaca Mw 7.8 Northern Chile IID earthquake. We observe that in some areas of the Santiago Basin, high PGA values can reach values close to 1 g, in which, in addition to directivity effects and takeoff angles, the rupture distances (similar to 100 km) and soil type (C) play a key role in amplifying strong-ground motion. Finally, our findings highlight the importance of reproducing high-frequency time histories as a proxy to re-evaluate the seismic hazard due to large IID earthquakes.

Automated summary

Large intraplate intermediate-depth (IID) earthquakes in Chile are highly destructive to structures and have occurred throughout the country. While small and moderate IID earthquakes have been reported below Santiago in recent years, the possibility of large-magnitude events cannot be ruled out. This study investigates the strong ground motion generated by large-magnitude earthquakes below the Santiago metropolitan region, highlighting the importance of reproducing high-frequency time histories to reassess the seismic hazard.