The role of the East Asian active margin in widespread extensional and strike-slip deformation in East Asia

Abstract

East Asia is a region of widespread deformation, dominated by normal and strike-slip faults. Deformation has been interpreted to result from extrusion tectonics related to the India-Eurasia collision, which started in the Early Eocene. In East and SE China, however, deformation started earlier than the collision Oatest Cretaceous to Palaeocene), suggesting that extrusion tectonics is not the (only) driving mechanism for East Asia deformation. It is suggested that the East Asian active margin has influenced deformation in East Asia significantly. Along the margin, Cenozoic back-arc extension took place behind several adjoining arcs, implying eastward rollback of the subducting; slab and collapse of the overriding plate towards the retreating hinge-line. We show that extension took place along a c. 7400 km long stretch of the East Asian margin during most of the Cenozoic. Physical models are presented simulating overriding plate collapse and back-are extension. The models reproduce important aspects of the strain field in East Asia. For geometrical and rheological conditions scaled to represent East Asia, modelling shows that the active margin can be held responsible for deformation in East Asia as far west as the Baikal rift zone, located c. 3300 km from the margin.