Condiciones geológicas-geotécnicas de la cuenca de Santiago y su relación con la distribución de daños del terremoto del 27F

Abstract

The 27F earthquake of magnitude Mw = 8.8, affected a large area of Chile and left more than 2 million of homeless. In the metropolitan area, the most serious damage focused on older houses, however, significant damage was also presented in modern constructions. In order to identify the geological and geotechnical variables of the Santiago basin that influenced their seismic response, a survey of the distribution of the structures with damages in Santiago Province was performed, accounting for a total of 10705 houses and 560 larger structures damaged. In parallel, the characterization of geotechnical-geological basin conditions was performed including the following factors: depth of bedrock, water table, fundamental frequency and geological setting. Additionally, the influence of former waterways that may have generated deposits of loose or soft sediments was investigated. The results of the analysis indicated that major damage occurred in structures founded on fine soil deposits (unit VII) and volcanic ash deposits (unit VI). Also, a certain concentration of irreparable damage was evident in the end zone of unit IIIa (alluvial deposits), characterized in its final stretch by deposits of fine soils.