Abstract

In December 1990, southeastern Sicily was struck by a moderate earthquake (ML 5.4). The event and the subsequent aftershocks represent renewed activity for the Malta Escarpment fault system (MEFS) three centuries after the most recent of several large destructive historical earthquakes. An 11 yr period of quiescence was interrupted with a minor swarm in 2002 (Mmax 3.6). These sequences and regional seismicity were relocated through 3D tomography. The resulting velocity model indicates a velocity contrast in the vicinity of MEFS. High-precision relative relocations were derived by the cross-spectral method for 18 events from the 1990 sequence and 10 earthquakes from the 2002 swarm. These swarms were aligned along fault segments striking east-northeast–west-southwest, conjugate to the north-northwest–south-southeast orientation of the MEFS. We conclude that the MEFS is fragmented in segments with different seismic behaviors, and that great stress accumulation along the main segment of the MEFS is less likely.

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