Interseismic Coupling Along the Java-Timor Subduction-Collision Zone at East Indonesia

Abstract

The Java-Timor subduction-collision zone is one of the most tectonically complicated structures along the strike of the Indonesia-Australia convergence. This complexity makes it difficult to interpret observations of interseismic deformation. In this study, we simultaneously inverted 108 Global Positioning System velocities and 176 earthquake slip vectors to investigate the variation in interseismic coupling along the Java-Timor megathrust and the Flores-Wetar back-arc thrust. Our estimated coupling indicates two relatively wide coupled zones in the Nusa Tenggara segment of the megathrust and back-arc thrust of widths ∼198 and 90 km, respectively. Elsewhere, the widths of estimated coupled zones are narrower, but still indicate significant earthquake and tsunami hazards. The gaps in seismicity and estimated coupled zones along the Java-Timor megathrust are not obviously correlated. The highly coupled Lombok segment illustrates consistency with the occurrence of the 2018 Lombok earthquake sequence.