Analogue modelling of reverse fault reactivation in strike–slip and transpressive regimes: application to the Giudicarie fault system, Italian Eastern Alps

Sandbox analogue models were used to study the reactivation of a reverse fault in strike–slip and transpressive regimes, for comparison with the evolution of the Giudicarie fault system in the Central Eastern Alps. The Giudicarie system is interpreted as resulting from Late Miocene sinistral transpressive reactivation of an older, Late Oligocene reverse fault. The ‘old’ reverse fault was reproduced as a pre-cut dilatant surface obtained by pulling a stiff metal wire through the model sand layer. The position of the pre-existing fault with respect to the base plate fault accommodating the strike–slip and transpressive faulting phase controlled the extent and geometry of reactivation. The clearest reactivation in a pure strike–slip regime was achieved in experiments where the basal strike–slip fault was immediately below the pre-existing fault plane. This strong reactivation involved lateral extrusion and lateral stepping of secondary faults from the basal fault to the pre-existing reverse fault. In the case of transpression, the most spectacular reactivation was achieved for a convergence angle of 10°. Strongly asymmetric structures developed on either side of the pre-cut dilatant zone. The analogue experiments reproduced very closely the structural features of the Giudicarie fault system, supporting a model involving a twofold tectonic evolution for the Giudicarie fault system, with later reactivation in sinistral transpression of an older reverse fault.