Abstract

In the frame of E.G.T. (European Geotraverse Project) a seismic wide angle profile was recorded in 1985 from the eastern Tunisia up to the Pantelleria trough, using 15 Ocean Bottom Seismometers (OBS) and explosive sources, both in the mainland and offshore. In this study the OBS records, which so far remained unpublished, are interpreted giving a description of the crustal structures along a transect about 100 km long oriented SW-NE and reaching the southwestern margin of the Pantelleria rift zone (or Sicilian Channel Rift Zone-SCRZ). The Moho boundary uplifts northeastwards, its depth ranging between 25 and 20 km. In this sector the upper mantle is characterized by a low seismic velocity of about 7.6 km/s. A flat, deeper discontinuity in the upper mantle was also interpreted at the depth of about 30 km; below this latter boundary the velocity reaches the value commonly found in the upper mantle (8.1 km/s). In order to attempt the building of a geophysical model of the whole transect from Tunisia to Sicily, other seismic published data were used together with the regional Bouguer anomalies. The Moho is 28 km deep beneath the Tunisian coastline and at 34 km under Sicily. In both these areas the velocity of the upper mantle is of about 8.0-8.1 km/s, therefore normal, in contrast with the structure found across the SCRZ (low velocity of about 7.6 km/s and 20 km deep). The crustal structure shown by the model is clearly asymmetrical, the northeastern flank of the uplifting Moho being steeper than the one towards Tunisia. A comparison of this model with the published interpretations of transects across other rifts shows analogies (uplifting of the upper mantle together with low seismic velocity) with the crustal structure of some segments of the Afro-Arabian rift, especially in the Red Sea, where the process of rifting is relatively young and in progress.

You do not currently have access to this article.