Pre-existing cross-structures and active fault segmentation in the northern-central Apennines (Italy)

摘要: Abstract The multideformed axial zone of the Apennines provides a great opportunity to explore influence pre-existing cross-structures (inherited from pre-Quaternary tectonic phases) on segmentation Quaternary/active seismogenic extensional faults. Detailed geological and structural data their comparison with seismological show that although attitudes (strike dip) oblique faults are certainly an important factor in determining segment boundary, size inherited structures seems be more crucial. Pre-existing lengths ranging several kilometers few tens twofold behavior. They can act as barriers during rupture single fault or they reactivated transfer zones inducing activation two adjacent segments belong same system. Regional basement/crustal cross-structures, hundreds (commonly NNE-striking), may “persistent barriers” halt both system propagation, thus terminations maximum sizes. In northern-central Apennines, NNE-striking Ancona–Anzio, Valnerina, Ortona–Roccamonfina lineaments, having been repeatedly since Mesozoic, represent most examples these structures. Moreover, probably due misorientation respect present stress field, regional appear less likely produce strong magnitude events (no surface evidence for Quaternary faulting has found far historical instrumental seismicity shows only M ~ 7 event, other hand, is occur along (N)NW–(S)SE trending normal systems. Lastly, we propose model explain different sizes systems basis location spacing. this view, our results contribute reasonable assessment nature future ruptures which critical importance estimating seismic hazard.