GNGTS 2013 - Atti del 32° Convegno Nazionale

with a dynamic process where indentation and lateral extrusion involve slips at crustal depths ranging between 10 and 30 mm/yr. The available velocity data are consistent with slip taking place on at least six rectangular faults located in the upper crust: we associate them primarily with the Giudicarie Fault, the North Alpine Wrench Corridor, the Brenner fault, the SEMP fault along the northern part of the Tauern window, the Pustertal-Gailtal fault and the Dinarides, e.g., the Idrija and the eastern segments of the Fella-Save faults (Fig. 2). Whereas most of these zones represent well defined fault zones, the North Alpine Wrench Corridor corresponds to a zone of distributed seismicity close to the northern margin of Eastern Alps (Reinecker and Lenhardt, 1999; Lenhardt et al. , 2007) and consequently a zone of distributed deformation. Using the root mean square (r.m.s.) of the (observed-minus-modeled) velocities as an indicator of the goodness of the fit, we constrain the geometrical parameters of the rectangular faults and slip rates. There are nine parameters for each fault: three dimensional coordinates of an origin, length and width of the fault, two-dimensional slip vector, strike and dip angles. The least squares adjustment is done on a neighborhood of a priori values of these parameters, which come from independent information such as structural geology, average direction of P/T axes of fault plane solutions, and regional strain rate field from GPS velocities. Fig. 2 – Geometry of the six rectangular slip planes (grey rectangles) projected onto the topographic surface. The grey line parallel to one of the sides of each rectangle represents the intersection of the fault plane with the topographic surface. The ‘beach balls’ give a pictorial view of the data in Tab. 1. The number in black above each beach ball refers to the indexing in Tab. 1. The blue arrows represent the measured velocities with 1 error ellipse, and the white arrows the predicted model velocities based on Tab. 1. To = Tonale fault, PG = Pustertal-Gailtal, Gi = Giudicarie fault, TW = Tauern Window, NAWC = North Alpine Wrench Corridor, La = Lavant Fault, MF = Möll Valley-Hochstuhl fault, Di = Dinarides, Mo = Montello, Fr = Friuli, SEMP = Salzachtal-Ennstal–Mariazell–Pu- chberg fault, Go= Görtschitztal fault, IdF= Idrjia fault, KF= Katschberg Fault. Vergence and faults style are from the Structural Model of Italy (CNR, 1990). 159 GNGTS 2013 S essione 1.2