Interseismic coupling, stress evolution, and earthquake slip on the Sunda Megathrust

The extent to which interseismic coupling controls the slip distribution of large megathrust earthquakes is unclear, with some authors proposing that it's the primary control and others suggesting that stress changes from previous earthquakes are of first order importance. Here we develop a detailed stress history of the Sunda Megathrust, modified by coupling, and compare the correlation between slip and stress with that of slip vs. coupling. We find that the slip distributions of recent earthquakes are more consistent with the stress field than with the coupling distributions but observe that, in places, the stress pattern is strongly dependent on poorly constrained values of slip in historical earthquakes. We also find that, of the 13 earthquakes in our study for which we have hypocentral locations, only 2 appear to have nucleated in areas of negative stress and these locations correspond to large uncertainties in the slip distribution of pre-instrumental events.