Relazioni tra le faglie quaternarie e la sismicità nella dorsale appenninica umbro-marchigiana: l'area di Colfiorito

Combined analysis between structural, geomorphological data and remote sensing interpretation confirm an extensional Quaternary tectonic regime in the Colfiorito area (Umbria- Marche Central Apennines). It is characterised by a maximum principal axis of finite strain oriented about NE-SW, which is the result of a progressive deformation process realised by the superposition of incremental extension also oriented NNE-SSW. Surface geological data, crustal tectonic setting (recon- structed using CROP 03 seismic reflection profile) and seismo- logical data relative to Autumn 1997 Colfiorito sequence con- strain the proposed seismotectonic model. We interpreted the seismogenetic SW-dipping low angle normal fault as an inver- ted thrust ramp located in the basement between 5-10 km. Surface projection of this seismogenetic structure define a crustal box where the high angle normal faults realised the uppermost crust deformation. Regional pattern of pre-existing basement thrust planes control the seismotectonic zoning. This zoning is not directly related to the high angle normal fault system which can be continuous through different crustal boxes, because they represent the re-activation of pre-existing normal faults. Moreover, Quaternary slip-rates relative to high angle normal faults in the Central Apennines are closely related to seismic hazard within each crustal box.