Source parameters of earthquakes in the Strait of Messina, Italy, during this century

Basic source parameters of earthquakes that have occurred in the seismogenic source region of the Strait of Messina, southern Italy, are analyzed from seismological data and vertical ground displacements. In particular faulting parameters associated with the 1908 Ms = 7.1 Messina earthquake have been analyzed through inversion of coseismic displacements and available seismograms. This normal faulting earthquake was located in the upper 15 km of the crust, and had a source dislocation of 1.5 m on a fault plane striking N-S, and dipping 40° E. This seismogenic region was quiescent before 1908 and later on this century, but its surroundings, i.e. the southern segment of Calabrian arc, is one of the most seismically active regions of Italy, with sequences of large earthquakes (M = 7-7.5) in 1638, 1693, 1783 and 1905, probably also associated with normal faulting, as suggested by the regional tectonics. During this century in the Strait of Messina small earthquakes occurred in 1952 (ML = 4.5), 1961 (ML = 4.7), 1975 (ML = 4.7) and in 1985 (ML = 4.1), this last being the first documented swarm sequence. Hypocenter distribution, fault-plane solutions, seismic moments and stress drops have been computed from the data of a local seismic network consisting of up to eight stations. The scaling law of the swarm events seems to show a departure from self-similarity, with earthquakes having a constant source radius of about 300 m. © 1989.