Deformation and uplift at the transition from oceanic to continental subduction, Sumba Island, Indonesia

The transition along the strike of Sunda subduction zone, from oceanic in west to continental Australian lithosphere east is envisioned as one canonical examples structural changes that take place within an overriding plate when a wedge enters zone. Yet, along-strike offset trench toward margin represents response opposite predictions numerical models. To understand this paradox, we analyse morphotectonic evolution Sumba island located at Indo-Australian subduction. Drainage allows us constrain topographic since Pliocene. Flights uplifted coral reef terraces document Quaternary deformation. Focal mechanisms shallow crustal earthquakes current stress field. Together, these data reveal affected by dextral en-échelon folding. Offshore, island, reverse and strike-slip focal evidence active transpressional emergence shearing accretionary prism were triggered western lateral boundary margin. We contend Plio-Quaternary tectonic region, with transpression migration primarily dictated shear transfer lower plate, favored strong interplate coupling, southwestward escape Savu-Sumba block following impingement against Timor island.