Vulnerable areas determination based on seismic response at Chile center region

Abstract

Chile is one of most seismic countries in the world. In the past 100 years, more than 8 major seismic events occurred in Chile, with the coastal area of central Chile being one of the most affected Since 2007, nearly 2,306 earthquakes were recorded in this area with magnitudes varying between 1.9 and 6.9 in the Ritcher and Mercalli scales. The earthquakes’ impact on the engineering structures depends on several factors, such as: the depth of the wave, wave type, geomorphological aspects of the rock, and soil properties. Chile central region of is a very important economics area, but at the same time, very vulnerable. The cities existing on this area, are installed in coastal plains, limited by Coastal Mountains and Pacific Ocean. Most of the seismic activity episodes recorded by Nacional Seismological center (CSN) is on the ocean. The present research aims to identify the regions vulnerable to significant seismic activities based on the average shear wave velocity on the upper 30m (Vs30) and using Geographic Information Systems. The Vs30 values were measured by the United Stated Geological Service (USGS). This analysis is based on the topography, geological units classified by Chilean norms NCh433, NCh2369, and law decree 61/ 2011. The analysis indicated that last epicenter city, Cobquecura, is the low vulnerable area, considering high Vs30 values and low number of habitants. Cities as Concepción, Talcachuano, San Pedro de la Paz, Coronel y Hualpén are more vulnerable because low Vs30 values, and high population. This factor can be associated to river mouths and floodplains presents in this area.