Seismotectonics and present seismic hazard in the Tuscany-Romagna-Marche-Umbria Apennines (Italy)

摘要

The Tuscany-Romagna-Marche-Umbria Apennines host major seismic zones that have generated several strong earthquakes. We argue that such activity is an effect of the relative motion between the outermost sector of the Romagna-Marche-Umbria units and the surrounding zones. This interpretation is consistent with the pattern of post-early Pleistocene deformation and the present velocity field, inferred from geodetic observations. The last evidence, being derived by a fairly dense network of permanent GPS stations, allows a good definition of the outer Apennine sector which is characterized by a significantly higher velocity (4-6 mm/y, roughly NE ward) with respect to the inner belt (1-2 mm/y, roughly NNW ward). The fact that the main seismic zones are just located along the inner and outer boundaries of the extruding wedge is compatible with the proposed seismogenetic mechanism. Taking into account the tectonic setting in the Apennine belt and the possible effects, in terms of post seismic deformation, of the recent (since 1930) seismicity distribution in that zone, an attempt is made at recognizing which fault systems in the northern Apennines may be most prone to next major shocks (M > 5.5). (C) 2015 Elsevier Ltd. All rights reserved.