Crustal structure and seismotectonics of central Sicily (southern Italy): new constraints from instrumental seismicity

摘要: SUMMARY In this paper, we propose a new model of the crustal structure and seismotectonics for central Sicily (southern Italy) through analysis depth distribution kinematics instrumental seismicity, occurring during period from 1983 to 2010, its comparison with individual geological structures that may be active in area. The analysed data set consists 392 earthquakes local magnitudes ranging 1.0 4.7. We defined new, detailed 1-D velocity relocate occurred Sicily, calculated Moho 37 km mean VP/VS ratio 1.73. relocated seismic events are clustered mainly area north Caltanissetta (e.g. Mainland Sicily) northeastern sector (Madonie Mountains) study area; only minor greatly dispersed seismicity is located western sector, near Belice, along southern coast, between Gela Sciacca. hypocentral depicts bimodal pattern: 50 per cent occur within upper crust at depths less than ∼16 km, 40 middle crust, 16 32 remaining 10 subcrustal depths. energy release pattern shows similar distribution. On basis kinematic 38 newly computed focal plane solutions, two major geographically distinct seismotectonic domains distinguished: Madonie Mountain domain, prevalent extensional extensional-oblique associated Late Pliocene–Quaternary faulting, compressional compressional-oblique thrust mid deep depth, north-dipping Sicilian Basal Thrust (SBT). stress inversion solutions integrated neighbouring mechanisms available literature highlights regional homogeneous tensor, subhorizontal NNW–SSE-striking σ1 axis. In addition, on geodetic data, domain attributed SSE-ward thrusting block SBT plane. Seismogenic shearing mid-crustal was responsible unexpected Belice 1968 earthquake (Mw 6.1), evident implications terms hazard assessment.