Late Cenozoic deformation of the Eurasian and Burma Plates due to subduction of the Indian Plate beneath SE Tibetan Plateau and Myanmar

Abstract:

The late Cenozoic tectonics of the southeastern Tibetan Plateau and surrounding regions needs to be evaluated within the context of a larger dynamic system related to the subduction of the Indian oceanic lithosphere beneath Myanmar and Yunnan. The details of the geodynamic processes involve mantle flows associated with rollback and tears (which probably occur both laterally and horizontally) of the Indian slab with consequent effects on the geology of the overriding plate. These effects include: 1) volcanism in Tongchong, Yunnan Province, 2) clockwise rotational deformation of the overriding plate and 3) Burma Plate capture. In this talk we will present the strain rate throughout the region with a moment tensor summation of earthquake data. The deformation of SE Tibet, Yunnan and western Sichuan constitutes a distributed N-S oriented dextral shear zone with clockwise rotations up to 1.7° per million years. It is the clockwise vorticity relative to south China that accounts for the relative northward motion of India at a rate of 38±12 mm/yr at the Himalayas. Relative to south China, there is no southeastward extrusion of crustal material beyond the eastern margin of the Tibetan Plateau. Studies on earthquake seismic moment data, fault-slip data, and GPS measurements all show a clockwise rotational motion of SE Tibet, Yunnan, western Sichuan and eastern Myanmar around the EHS. The mirror image of this situation that is occurring today is the counterclockwise rotation of Anatolia, which is associated with the rollback of the Hellenic and Cyprian Trenches. In this talk we will also discuss the extreme oblique convergence between Indian and Burma plates and one of the effects of the oblique subducation is the transfer of right-lateral strike-slip faulting to the Indo Burma Range, one of the largest GeoPRISMs on Earth.