Seismogenic zonation as a branch of the logic tree for the new Italian seismic hazard map - MPS16: a preliminary outline
The zonation presented in this study has been developed with the aim of applying it as a branch of the logic tree that will be used for the new Italian seismic hazard map, presently in preparation according to the approach of seismotectonic probabilism. With respect to the zonation used for the present official seismic hazard map of Italy, the zonation proposed here considers narrower sources and is based on new and updated seismological data. In particular, some new seismogenic zones are proposed here, introducing areas that were not considered seismogenic until now (e.g., the narrow sources characterised by the presence of transform faults which are almost normal to the trend of the northern Apennines). The preliminary seismic hazard estimates produced with this new zonation aim to identify possible problems that the zonation introduces in the seismicity characterization of the seismogenic zones. As the present seismic hazard assessment was computed by considering a different attenuation model with respect to the one applied for the previous national seismic hazard maps, a re-elaboration of the most recent map referring to Italy has been developed: the comparison of the two maps is a good indicator of the areas where additional seismological investigation is needed to support the zonation presented here. In particular, some zones are not adequately documented with regard to seismicity and a different computation of the seismicity rates is suggested.