Fault orientation variations along the strike of active normal fault systems in Italy and Greece: Implications for predicting the orientations of subseismic-resolution faults in hydrocarbon reservoirs

Abstract

The orientations of subseismic-scale faults vary systematically along the strike of basin-bounding, active normal faults in Italy and Greece. A total of 16,272 outcrop measurements of the strike and dip of fault planes and their associated slip vectors indicate oblique slip near the lateral fault tips of the normal faults; subseismic faults vary in orientation to accommodate this slip. If viewed in map view from the footwall looking toward the hanging wall, right-lateral slip occurs at the left end of the faults, with left-lateral slip at the right end. Overall, slip vectors converge toward the hanging wall, with intersection lines for faults accommodating this slip parallel to the slip vector. If the same faulting style applies elsewhere, the empirical relationships presented herein can be used to calibrate results from mechanical fault models and provide a pragmatic guide to the orientations of normal-fault-bound compartments of rock in subsurface hydrocarbon reservoirs, given that the offsets across such faults may be below seismic resolution and not amenable to direct measurement.