IONIAN BASIN AND CALABRIA ARC - SOME NEW ELEMENTS FROM DSS DATA

The interpretation of results from a 250 km long seismic refraction traverse recorded using ocean-bottom seismometers in the northwestern Ionian Sea and a fan profile recorded across southern Calabria have augmented previous studies by placing additional constraints on the Tyrrhenian Sea-Calabria-Ionian Sea transition. Overlapping branches of P(n) phases confirm the existence of a thinned crust (about 13 km) giving rise to the major Bouguer anomaly high of the central Ionian Basin. A low average crustal velocity is observed throughout the basin, in accordance with the very thick sedimentary cover exemplified by previous seismic surveys. A deepening Moho may be followed continuously from the centre of the basin to 40 km offshore from Calabria where a sudden depth decrease (30 to 20 km) is accompanied by a sharp change in the crustal velocity structure. The estimated depth of such a shallower Moho towards the northwest, confirmed by a shot recorded in a fan geometry across southern Calabria, is in accordance with that found earlier for the southernmost margin of the Tyrrhenian Basin.