Historical damage pattern and differential seismic effects in a town with ground cavities: A case study from Southern Italy

This paper presents the results of a study focused on the analysis of differential seismic effects on a town characterized by the presence of ground cavities. The event analysed is the 1930 Irpinia earthquake (Io=X MCS; Me=6.7), whereas the site investigated is Rionero in Vulture (Basilicata, Southern Italy). This town is built, as several historical centres over the world, on man-made ground cavities going back to the past centuries. Due to the high-quality of available historical information regarding the 1930 seismic event, the analysed town represents an important case-study both to improve the reconstruction methodology of the damage ‘scenario’ and to test the role that ground cavities play on seismic damage in a site with high seismicity. To this purpose, we examined about 1400 unpublished technical reports. The information, drawn from written sources, was integrated with in situ surveys. Furthermore, we made a comparison with seismic effects which were recorded in some Italian localities having ground cavities. The results of this research can provide useful information for microzonation analysis and decision making for localities where seismic, territorial and anthropic features are similar to Rionero in Vulture. The paper is divided into four parts: the first one analyses the geological features of the region and the town; the second part describes the historical seismicity of the site; the third part deals with the methodological approach in order to reconstruct the building damage; finally, the fourth part is focused on the analysis of the damage pattern with appraisals of the causes of differential effects.