GNGTS 2017 - 36° Convegno Nazionale

GNGTS 2017 S essione 1.2 163 Fig. 3 - 3D fault model building of the northern sector of the CISS (Central Italy Seismic Sequence 2016-2017). The reconstruction is in progress and to be submitted by Lavecchia et al. to Tectonics. The hypocentral data set is from Chiaraluce et al. (2017). 1 - Deep geometry of the central Italy fault pattern and primary/secondary role of the co- seismic ruptures. 2 - Passive versus active role of pre-existing and long inactive fault discontinuities within the hypocentral area and their role in driving primary events or exclusively in localising subsidiary low-magnitude events and back-ground seismicity. 3 - Tectonic control played onto the time-space evolution of a seismic sequence by structural complexities such as sharp bends along strike or dip of an individual fault, interaction and linkage between overstepping fault strands, fault leakages, intersection between parallel or transversal faults, role of tectonic-controlled basal detachments. 4 - Structural style of the active and potentially seismogenic extensional tectonics in central Italy, at the light of the geometric similarity among the CISS and AQSS fault systems, both characterized by WSW-dipping high-angle normal faults detaching onto an east- dipping basal detachment. Some of our results concerning the 3D geometries of the AQSS and the CISS are shown in Figs. 2 and 3, where the similarity in scale and size between the two situations appears rather evident. The proposed reconstruction highlights the important role played at regional scale, in Quaternary times, by the east-dipping detachment, which coincides with the southern prosecution of the Altotiberina fault in the Vettore-Gorzano area and with the Latium-Abruzzi Extensional Detachment (LAED) beneath the AQSS (Lavecchia et al. , 2017) (Fig.1a). In both cases, the reconstructed geometry shows an along-dip ramp-flat-ramp configuration, which can open to the possibility of significant mid-crust earthquakes eventually released on the moderately steep segments of the basal detachment (40-45° dip). Such a preliminary hypothesis needs to be further investigated as it might contribute to partially fill the deficit in seismic release (Mulargia, 2013) observed within the intra-Apennine extensional province when only considering the well-known west-dipping high-angle faults.