Microtremors' HVSR and its correlation with surface geology and damage observed after the 2010 Maule earthquake (Mw 8.8) at Talca and Curicó, Central Chile

Abstract

Nowadays, microtremors' horizontal-to-vertical spectral ratio (HVSR) has been extensively used in the estimation of the predominant vibration frequency of soils, mainly for microzonation purposes. In the present study, we show results from extensive microtremor measurements performed at the cities of Talca and Curicó, Central Chile. We found a strong correlation between surface geology and microtremors' HVSR, even in complex geological settings. Considering the damage produced by the 2010 Maule earthquake (Mw 8.8), we also estimated high-density macroseismic intensities at these cities, with values ranging from VI up to VIII on the MSK64 scale. We believe that the main responsible of these variations are the surface geological conditions, also reflected in the variations of the resonance frequencies of the soils. The evidence presented here supports the use of microtremors' HVSR in combination with surface geology to improve seismic microzonation studies, particularly in an Andean context.