Reconstructed seismic and tsunami scenarios of the 1905 Calabria earthquake (SE Tyrrhenian sea) as a tool for geohazard assessment

Italy is one of the most seismically active regions in the central Mediterranean and one of the countries with the longest record of historical earthquakes in the world. Over the last decades the scientific community has recognised the value of historical data when used to constrain modelling tools in hazard analyses. This is the case of the destructive 1905 Calabria (South Italy) earthquake, followed by a tsunami and by many secondary effects on the environment observed both inland and offshore. Recently acquired geophysical data allowed to identify an active normal fault, named Sant'Eufemia Fault, located nearshore in the Sant'Eufemia Gulf (SE Tyrrhenian sea), considered the most probable seismogenic source of the 1905 earthquake and capable to trigger future events. In this paper we perform a scenario-based deterministic analysis for an earthquake resulting from the rupture of the Sant'Eufemia fault (SEF) and a preliminary potential risk analysis. After defining source parameters compatible with the 1905 earthquake (ca. 40 km fault length and ca. 2.3 m slip, Mw 6.9), KF-analysis and tsunami simulations are carried out and modelling results are compared against historical available data. The obtained results allow one to border areas in central Calabria that are most exposed to geohazard deriving from the analysed fault. Some of these areas happen to be zones with intense economic/touristic and urban development, which calls for the need to integrate the ongoing development plans with adequate programs of risk mitigation and prevention.