Soil-structure interaction scenarios in Lefkas Old Town (W. Greece)

In this work seismic damage scenarios were developed in the Lefkada Old Town (LOT). LOT is the historical centre of the capital of Lefkas Island, part of the Ionian Islands, which is one of the most seismically prone areas within the Mediterranean region, that suffered numerous devastating earthquakes in the past. The most recent strong earthquake with Mw=6.2 occurred on 14 August 2003 at a distance of about 13 km from LOT. A PGA=0.42g was recorded in LOT, one of the largest values recorded in Greece. Nevertheless, it produced limited damage to its buildings, comprising traditional construction practices of architectural significance and a high seismic behaviour as a rule. Towards the development of damage scenarios the following tasks were performed: (a) buildings inventory and vulnerability indices determination using EMS-98 and behaviour modification scores (b) subsoil response functions and 1D visco-elastic models calculation using microtremors (c) stochastic PGA simulation using site amplification deduced from the subsoil response functions. Two scenarios were developed considering the sources of the 2003 M6.2 earthquake and a future M7 event, located at the same fault. The discrete damage probability was resolved by formulating a beta distribution of an average damage grade related to the vulnerability index and the simulated PGA through empirical equations. The deduced models are comparable with the observed 2003 damage distribution, hence they are likely useful for preparing future emergency plans. In the aftermath, although further investigation is needed to explain outliers, the implementation of the followed methodology into an automated procedure for near real time shake and damage maps generation in case of a seismic crisis is highly recommended. The work herein, with proper adaptations, is potentially fairly applicable for other towns and regions in Europe