Raphaël Normand, Guy Simpson, Abbas Bahroudi

In the Makran subduction zone, earthquake focal mechanisms and geodetic data indicate that the deforming prism currently experiences N-S compression. However, paleostress inversions performed on normal faults observed along the coast reveal local stress components consistent with N-S extension. Previously proposed mechanisms such as gravitational collapse are not in line with N-S compression and surface uplift. We propose that the observed kinematics result from transient stress reversals following large earthquakes. During the interseismic period (now), the region experiences N-S compression. However, following a large reverse rupture on the subduction interface, stresses in the inner wedge relax, enabling a brief period of extensional faulting before a compressive stress state is reestablished. This mechanism, observed in other subduction zones, requires low overall stresses in the upper plate and that the margin ruptures in large megathrust earthquakes that result in nearly complete stress drops.