The 28 December 1908 Messina earthquake was a normal faulting event, which produced considerable vertical displacements. Three levelling surveys, having an overall extension of 125 km in Calabria and Sicily, were performed by the IGMI (Italian Military Geographical Institute) shortly before the occurrence of the main event and during the first months of 1909. Vertical subsidence up to 70 cm was measured, at bench marks located close of Messina. The inversion of the observed displacements has been performed by using a model consisting of uniform dislocation on one or more rectangular faults and the mathematical formalism developed by Matsu'ura and Hirata (1982).
Results indicate that the observed displacements are well modeled by a normal fault, oriented about NS, with a dislocation of 1.5 m, dipping 39°E. This fault is located beneath the Messina Straits, with the upper end at 1 km depth and crossing to the city of Messina. This model gives a seismic moment Mo = (4.9 ± 0.8) × 1026 dyne × cm and shows a good agreement with the fault plane solution derived from the long period P-wave first arrivals.