Earthquake relocations, crustal rheology, and active deformation in the central–eastern Alps (N Italy)

Abstract

A revised seismic catalogue (1994–2007) for the central–eastern Alps (N Italy) is presented. 396 earthquake relocations, for local magnitudes in the 1.2–5.3 range, are performed using a 3D crustal velocity structure and probabilistic locations. The location procedure is validated by computing a set of 41 quarry shot solutions and all the results, both about shots and seismic events, are compared with those obtained using the routine location procedure. Results are shown for five contiguous seismotectonic domains, as supported by geological and geophysical evidence (e.g., fault systems, crustal tomography, focal mechanisms types). Earthquake hypocentres are mostly located in the upper crust (0–15km of depth), in good agreement with thermo-rheological models about the brittle–ductile transitions (8–9km of depth) and total crustal strengths (1.0–2.0TN m−1). Epicentres are clustered and/or aligned along present-day active geological structures. The proposed seismotectonic model shows dominant compression along the Giudicarie and Belluno–Bassano–Montello thrusts, with strain partitioning along the dominant right-lateral strike-slip faults of the Schio–Vicenza domain. The present-day deformation of the Southern Alps and the internal Alpine chain is compatible with Adria indentation and the related crustal stress distribution.