Focal mechanism inversion in the Giudicarie–Lessini seismotectonic region (Southern Alps, Italy): Insights on tectonic stress and strain |
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Authors: | Alfio Vigan , Gianni Bressan, Giorgio Ranalli,Silvana Martin |
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Affiliation: | aDepartment of Chemical and Environmental Sciences, Insubria University, Via Valleggio 11, 22100, Como, Italy;bIstituto Nazionale di Oceanografia e di Geofisica Sperimentale, Dipartimento Centro Ricerche Sismologiche, Via Treviso 55, 33100, Cussignacco (Udine), Italy;cDepartment of Earth Sciences and Ottawa-Carleton Geoscience Centre, Carleton University, Ottawa, Canada K1S 5B6 |
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Abstract: | 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 (MD) 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 L) 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. |
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Keywords: | Focal mechanisms Seismotectonics Tectonic stress and strain Southern Alps |
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