Detection of local site effects through the estimation of building damages

Abstract

After the Umbria Marche seismic sequence of September–October 1997, an extensive microzoning study was conducted, from October 1997 to May 1998, to detect the zones where the ground motion was amplified because of local geological and geomorphological settings. The goal of the investigation was to return amplification coefficients to local authorities for the post-seismic reconstruction and repairing of pre-existing buildings, by examining the seismic behaviour of the most damaged 60 villages. The analysis consisted in the application of well known computer codes and the results were arranged as reference table, used to assign the amplification coefficients to the rest of damaged localities. The present study has the aim of evaluating the accuracy of that methodology, following a completely different approach. The actual damages, detected by an aerial photo interpretation, are compared to the theoretical damages estimated through empirical curves, obtained from the analysis of recent Italian earthquakes. This approach was reliable enough to calibrate the results of the microzoning study and appropriate when an immediate assessment of the damage is required, to assign funds and estimate the amplification zones, that need to be investigated in finer detail.