Combined effects of Eurasia/Sunda oblique convergence and East-Tibetan crustal flow on the active tectonics of Burma

• There is no active subduction along the Arakan Ranges but mainly gravity tectonics.
• The India/Sunda right lateral shearing affects the whole Burma platelet.
• The Burma platelet was bent westward due to lateral effect of the Tibetan Plateau collapse.
• Both GPS and seismic data show that part of the Tibetan crustal flow is deviated towards Myanmar.
• The Burma platelet is affected by both the Tibetan collapse and the N10°E India/Sunda convergence.

It is widely accepted that deformation of the India/Sunda plate is the result of partitioned hyper oblique convergence. Presently, sub-meridian dextral strike slip faulting accommodates this India/Sunda motion in a buffer zone, the Burma platelet. This wide dextral strike slip shear zone is complicated by the side effect of the Tibet plateau collapse that can be described in term of crustal flow and gravity tectonics. The loss of potential energy related to this plateau collapse affects most of the Burmese platelet particularly in its northernmost part.Interaction of these two distinct geodynamic processes is recorded in the GPS based regional strain field, the analysis of seismic focal mechanism but also from direct geologic observations both onshore and offshore Myanmar and Bangladesh.We propose the apparent E–W shortening component of this so called partitioned hyper-oblique subduction is only the effect of regional gravitational forces related to the Tibet plateau collapse whereas the NS strike slip faulting accommodates the India/Sunda motion.