Historical variables of seismic effects: economic levels, demographic scales and building techniques

During the analysis of the historical seismicity of Italy, territorial and social elements emerged that in the long term have strongly influenced the effects of the earthquakes. These elements are here presented as historical variables of the degree of intensity. The Italian context is characterised by a long and continuous history of housing, with profound historical and economic changes. The effects of the earthquakes are influenced by population density, the verticalism of the buildings - from the thirteenth century - and the building techniques. The latter have always been highly diversified, not only in the various historical periods, but also within the same time-span, on the same territory, because of the strong geographic differences which characterise the Italian area (coasts, mountains, plains, etc.). This contribution provides a synthetic assessment of these variables in relation to the seismic effects described in the historical sources. The authors expect to be able to better calibrate in future the evaluation of the seismic effects in relation to building characteristics.