Focal mechanism inversion in the Giudicarie-Lessini seismotectonic region (Southern Alps, Italy): Insights on tectonic stress and strain

摘要

A set of 41 focal mechanisms (1989-2006) from P-wave first polarities is computed from relocated seismic events in the Giudicarie-Lessini region (Southern Alps). Estimated hypocentral depths vary from 3.1 to 20.8 km, for duration magnitudes (M-D) in the range 2.7-5.1. Stress and strain inversions are performed for two seismotectonic zones, namely G (Giudicarie) and L (Lessini). This subdivision is supported by geological evidence, seismicity distribution, and focal mechanism types. The available number of data (16 in G, 22 in Q does not make possible any further subdivisions. Seismotectonic zones G and L are undergoing different kinematic regimes: thrust with strike-slip component in G, and strike-slip in L Principal stress and strain axes in each sub-region show similar orientations. The direction of maximum horizontal compressive stress is roughly perpendicular to the thrust fronts along the Giudicarie Belt in zone G, and compatible with right-lateral strike-slip reactivation of the faults belonging to the Schio-Vicenza system in zone L On the whole, kinematic regimes and horizontal stress orientations show a good fit with other stress data from focal mechanisms and breakouts; and with geodetic strain rate axes.