1ST STUDY OF THE MICROSEISMICITY OF CORSI CA ISLAND WITH DATA-D FROM A REGIONAL SEISMOLOGICAL NETWORK AND SISBALIG-II NETWORK

The establishment of a permanent 4-station network and a temporary 10- station network during the SISBALIG II survey, has allowed clarificati on of the microseismicity affecting the island of Corsica. The epicent ral map (61 events) indicates a microseismic zone oriented in a NNE-SS W direction that stretches from Zicavo region, in the south, to the ea stern plain and the Castagniccia area in the north. On the contrary, t he southern and northwestern parts of the island show little or no evi dence of activity. The eastern margin shows significant activity while the western margin is inactive. All events have a low magnitude (less than 4.3) and are located in the upper crust. Examination of the pola rities of the first motions of four seismic events leads to the deduct ion that three of these were extensional mechanisms, and the fourth sh ows a compressional mechanism that is probably associated with the loc al kinematics of fault blocks. These results suggest that Corsica is s ubject to an extensional regime that could be linked to resent-day ver tical movements and to the dynamics of the Tyrrhenian domain.