Structure and kinematics of the Indo-Burmese Wedge: Recent and fast growth of the outer wedge

The northern Sunda subduction zone, offshore Burma, and the associated Indo-Burmese Wedge mark the active eastern boundary of the Burma Platelet jammed between the India Plate and the Sunda Plate. The aim of this paper is to provide a structural and kinematics analysis of the Indo-Burmese Wedge based on seismic reflection, geodetic, and geological field data. We found out that the Indo- Burmese Wedge is the place of diffuse strain partitioning: right-lateral shearing in the innermost part and E-W shortening in the outermost part. In the outer wedge, thick-skinned deformation overprints thin-skinned deformation. It can be explained by the required preservation of the critical taper after the fast westward propagation of the outer wedge above a very efficient clayey decollement layer. The thick-skinned deformation is here characterized by major right-lateral strike-slip faults ( the Kaladan Fault and the Chittagong Coastal Fault) and yet a typical internal deformation of the Indo-Burmese Wedge. We suggest that the westward migration of internal right-lateral shear deformation allows preservation of the strain-partitioning ratios between internal N-S trending right-lateral shearing and external E-W shortening. Some seismic lines show that the outer wedge deformation is not older than 2 Ma. Its propagation could have been enhanced by the large amount of sediments filling up the Sylhet flexural basin formed after the Pliocene tectonic uplift of the Shillong Plateau. Citation: Maurin, T., and C. Rangin ( 2009), Structure and kinematics of the Indo- Burmese Wedge: Recent and fast growth of the outer wedge, Tectonics, 28, TC2010, doi: 10.1029/2008TC002276.