GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.1 GNGTS 2023 The 1908 Messina-Reggio earthquake: are we hitting the right road? A. Argnani 1 , N.A. Pino 2 1 ISMAR – CNR, Bologna, Italy 2 INGV - Sezione di Napoli, Napoli, Italy The M 7.1 earthquake that on the 28th December 1908 struck the cities of Messina and Reggio Calabria, facing each other across the Messina Straits, was one of the most destructive events of last century, and one of the deadliest earthquakes in human history, causing a huge death toll, estimated between 60,000 and over 100,000. None of the large earthquakes that occurred in Europe in the XX century, some of them with larger magnitude, resulted to be as deadly as the Messina earthquake, which sparked a wave of solidarity and grief throughout Italy and also worldwide, with the launch of international relief efforts. The earthquake was soon followed by large tsunami waves that swept the coast of eastern Sicily, reaching as far south as the island of Malta, and caused about 2000 casualties. The very early observations of Prof. Omori, that visited the devastated lands two months after the earthquake, suggested an offshore source for both the earthquake and tsunami (Omori, 1909). Over the years many scientists have attempted to identify the fault that originated the 1908 Messina Straits earthquake. The analyses accomplished so far provided some important constraints for the causative fault, but no comprehensive source model has been presented yet and no general consensus has been reached. Recent attempts to identify the surface rupture of the fault responsible for the 1908 Messina-Straits earthquake have proved poory reliable, in spite of echoes in the press. The limited seismological and geodetic data for the 1908 Messina-Reggio earthquake allow to constrain a low-angle, ca. N-S-trending and E-dipping fault, with a maximum length of ca. 40-45 km, and a northward propagation of the rupture from a depth of 8-10 km (e.g., Pino et al. 2009). Shallow seismic profiles indicate an indirect dating of the origin of the 1908 Messina fault and allow to reject the occurrence of a fault plane rupturing the seafloor. Therefore, geological and seismological data both point to a blind fault. In this respect a re-examination of the morpho-bathymetry of the Messina Strait is advisable, with a closer inspection at the morphology of the seabed which may have recorded signs of the activity of a blind extensional fault. In any case, any new interpretation cannot be based on a partial analysis or on arbitrary assumptions, without taking into account all reliable constraints based on available data and observations. In perspective, the acquisition of a deep seismic profile, possibly amphibian, crossing the Messina Strait could be a way to image the plane of the blind fault, although the tectonic complexity of the