Seismic Microzonation of an urban settlement of Central Italy: geological features and selection of a suitable amplification factor

ABSTRACT - The Mugello area (Tuscany-Italy) falls within one of the highest seismicity zones of the Northern Apennine Chain. It can be considered of medium-to-high seismicity when compared to the rest of the Italian territory and in the past has been affected by earthquakes reaching IX degree intensity on the MCS scale, with an estimated magnitude greater than 6 (e.g. the 1919 “Mugello earthquake” which caused widespread damage, even at great distances). To better address future decisions about town planning and land use, an in-depth study has been promoted by the Regional Government of Tuscany with the aim of drawing detailed maps of seismic microzonation for the most representative urban settlements in the area. Firstly, geological features, case histories of local effects during past earthquakes and results from geophysical tests were combined in order to draw a 1st level microzonation map; secondly, numerical 2D analyses were performed to quantify local seismic responses over selected soil sections and improve the level of microzonation mapping (3rd level). The paper describes results from the 1st level microzonation of Barberino, one of the most important towns of Mugello, together with remarks about the best way to summarize in the 3rd level map the amplification effects obtained from local seismic response analyses.