Macroseismic Attenuation in the Campanian Area, Southern Italy

The main objective of the present study is to evaluate seismic attenuation relationships for the Campanian area (southern Italy) using felt intensity report data obtained from a comprehensive historical databases (DOM 4.1). We focused our attention on the Campania region because it is characterized by a high seismic hazard and risk, particularly in the Naples area and its suburbs. In order to derive an attenuation relationship for the area we fitted the observed data by using several functions. We found that a linear plus logarithmic model gives the best fits for the data in the Campanian region. Most of the attenuation relationships proposed up to now for the Italian peninsula have an isotropic behavior and do not always properly describe the macroseismic attenuation. Therefore, in order to check a possible dependence of the attenuation on the azimuth of the seismic rays, we divided our data set in octants and performed for each of them the same analysis we did for the whole data set. The obtained results are different from octant to octant and the differences, besides being connected to source effects, could be interpreted as possibly due to the existence of crustal lateral variations at different depths of the lithological and physical features that could affect the attenuation patterns.