The Western Medi terranean differs considerably from the Eastern Medi terranean. This is due to the absence of modern active margins in the Western Mediterranean. Instead, there are separate basins underlain by oceanic or thinned continental crust, young in age. The Valencia Trough, the western part of the East-Balearic Sea, as well as the Alboran Sea are examples of such basins. These are the basins where the study areas are located. Insight about the geological structure of the Earth's crust in the study areas is obtained from the geological data from the adjacent land, marine drilling results, but mainly from geophysical data

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