Geodetic surveys across the Messina Straits (southern Italy) seismogenetic area

The Messina Straits, southern Italy, unfortunately became famous after the occurrence of the great earthquake of December 28, 1908, Ms=7.5, that caused thousands of deaths and severe destruction over a wide area along the Sicilian and Calabrian coasts. After that time many geophysical and geological studies were performed to evaluate the seismic characteristics of the 1908 earthquake, the seismic risk and the geological evolution of this region in the framework of Mediterranean geodynamics. In 1970, a geodetic network was set up across the Straits and was repeatedly measured with terrestrial techniques until 1980, showing a northward displacement of the Sicilian sites with respect to the Calabrian ones, between 1970 and 1971. In 1987, the old terrestrial network was surveyed again for the first time by the GPS technique, improving the accuracy of the coordinate determinations. Finally, in 1994, a wider network was established and surveyed again to collect additional GPS observations from a larger area across the Straits. In this paper, an analysis of the results obtained from the two GPS surveys with respect to those achieved by the terrestrial surveys (from 1970 to 1980) is given. This analysis shows there has not been significant crustal horizontal deformation across the Straits in the last 15 years. Although this crustal tectonic 'quiescence' corresponds to a low seismic activity level in the Straits area, terrestrial and GPS geodetic results would agree with Straits geophysical models excluding any aseismic deformations acting perpendicular to the Straits axis. (C) 1997 Elsevier Science Ltd.