Seismic susceptibility map for Cascais County (Portugal): a simple approach

Abstract

Cascais County, located in the central part of the Portuguese mainland, is a very attractive place due to its interesting and recognized natural and cultural heritage. Leisure and cultural activities attract many people every day, which leads us to the importance of safeguarding from possible risks. Taking into account the historical seismicity, in particular the damage caused by the 1755 earthquake and tsunami in Cascais, it becomes clear that the seismic risk is relevant in Cascais County. In this paper, we present a methodology to obtain a seismic susceptibility map based on a soil characterization study using the refraction microtremor technique and ambient vibration measures (H/V Nakamura technique). This kind of map gives a detailed picture of the zones that can suffer larger seismic ground motion that can be easily consulted and understood by technicians, making it a suitable work tool. Considering the extent and geological diversity of the area, we selected some representative sites to perform the experiments, taking into consideration the different surface geological formations, paying particular attention to situations with the greatest potential risk.