The Central Southern Alps (N. Italy) paleoseismic zone: a comparison between field observations and predictions of fault mechanics

摘要: Abstract The internal sectors of the Orobic Alps (Northern Italy) are characterised by Alpine age regional shortening showing a transition, through time, from plastic to brittle deformation. Thrust faults cut ductile folds and marked cataclasites and, locally, pseudotachylytes, suggesting that motion was accommodated seismic frictional slip. In Eastern thrusting initiated at depths deeper than 10 km (the emplacement depth Adamello pluton) possibly continued shallower depths. This demonstrates thrust occurred between brittle-ductile i.e., mid-crustal exhumed paleoseismic zone shows different geometries along strike. central Alps, faults, associated with have average dips around 40° show no pervasive veining. Much steeper thrusts (dips up about 85°) occur in eastern Alps. this area, not veining, fluid circulation relatively scarce. suggests faulting did supralithostatic pressure conditions. These reverse severely misoriented (far too steep) for fault reactivation sublithostatic regime. We suggest likely started when were less steep progressively rotated present day dips. Domino tilting is probably responsible subsequent steepening, as suggested decrease steepness north south systematic rotations previous structures consistently blocks. When became inclined beyond lock-up angle, further them. At later stages newly formed lower angle shear planes (dipping 30–40°), predictions mechanics.