Recent deformations and the seismogenic source in the Messina strait (Southern Italy)

Abstract

The relationships between mechanisms and mode of faulting in Pliocene and Pleistocene times and seismic release, are the basis for an interpretation of the growth of deformation energy in the Messina Strait. The major fault systems trending in NE-SW, NW-SE and E-W directions, divide blocks subjected to high mobility, in concurrence with greater uplifting of the Calabrian side with respect to Sicily across the two sides of the Strait. As revealed by structural analyses, the tectonic features of the area are dominated by normal faulting. Many synsedimentary features seem to indicate repeated and intermittent pulses of high-velocity fault slippage, possibly related to seismic shaking. When considering the seismic record it seems that the strongest shocks are generated by preferential strain accumulations along the NNE-SSW fault systems. From a geological standpoint, it seems clear that the largest events may be alternately related to either the NNE-SSW, E-W or NW-SE fault systems which dissect an extremely “cataclastic” upper crust. The recent deformations of the Messina Strait can be related to the large-scale processes induced by the overthrusting of the thinned Tyrrhenian crust over the thickened African crust, as suggested by seismic refraction profiles. Along the inner margin of the Calabrian Arc the deep deformation mechanisms are reflected by contrasting vertical movements between a stretched and downfaulted Tyrrhenian domain and an uplifted chain, with resulting large strain accumulations and seismic failure in the brittle upper crust.