The Experience of Seismic Microzonation in Lazio Region (Italy) Mountain Municipalities

Within the activities of seismic microzonation promoted and co-funded by Lazio Regional Administration (LRA) and the Department of Civil Protection (DPC), following the issues of the National rule OPCM 3907/2010, seismic microzonation studies were carried out in a set of municipalities, already attributed to the seismic Zone 1 (i.e. with the most severe level of seismic hazard and located in mountain areas). These municipalities show similar geologic and geomorphologic features as they are characterized by a local bedrock constituted of limestone and marly-limestone and fluvial-lacustrine deposits filling intra-mountain alluvial plains. The engineering-geological model of the subsoil as well as the jointing conditions of the outcropping rock masses were defined on the basis of available technical data from public reports, as well as from original geophysical surveys. Different types of microzones (i.e. stable, stable susceptible to seismic amplification and unstable areas) were identified according to the technical rules (ICMS 2008). Nevertheless, the experienced approach highlighted some critical features in the microzonation methodology that encourage future studies devoted to obtain the refinement of the operative procedures.