The resilience of traditional architecture: the anti-seismic constructive system of Lefkada Island

The Greek island of Lefkada is one of the areas in Europe with the highest seismic hazard, both for the frequency of events and their magnitude. The local traditional architecture is characterized by its particular resilience to earthquake thanks to a unique and effective anti-seismic constructive system. This system is based on two autonomous structures that act simultaneously, but independently: a massive stone structure, which primarily performs the load-bearing function and a secondary timber frame. The direct observation of the seismic behavior of the built heritage and the wise use of local materials, suitably used depending on their resistance characteristics, led over time to the development of an empirical solution, progressively recalibrated, which offers a seismic behavior of great interest. Numerous and in-depth studies of the dynamics and of the consequences of seismic events in 2003 and 2015 in Lefkada have highlighted that buildings which present this system and have been subjected to adequate maintenance over time, have shown greater resistance and lower damages than reinforced concrete buildings, recently built and conceived. The aim of the paper is twofold: on the one hand, it is intended to illustrate the constructive features of this system, which is a still alive and currently used tradition, the dynamics of its seismic behaviour and the level of resistance of the masonry. On the other hand, it aims to raise the awareness of designers to seismic improvements in the existing building heritage, which can take advantage of the residual seismic performance of the building and grasp at the suggestions of the past in the anti-seismic conception of contemporary construction.