A kinematic model of the Scotia plate (SW Atlantic Ocean)

Abstract

The focal mechanisms located around the Scotia plate were examined by fault population analysis to calculate both the trends of the maximum horizontal shortening on the plate and the orientations of its associated faults. The results show that both the northern and southern boundaries of the Scotia plate (the north and south Scotia ridges) are currently undergoing left-lateral movement. This movement induces a left-lateral shear couple in the whole plate, with a maximum horizontal NE–SW shortening direction. The established fault orientations and fault classes closely match the predicted structural pattern of a theoretical shear couple that includes the entire Scotia plate. The stress trajectories deduced from finite element modeling also agree with the proposed left-lateral shear couple model; the calculated stress trajectories are characterized by a homogeneous NE–SW compression direction over the whole Scotia plate. This shear model also explains the slip of recent tectonic structures found at the boundaries of the Scotia plate and suggests the possibility of reactivation of its former tectonic structures.