# Sub-crustal forcing on the tectonic and topographic evolution of collision-subduction transition zones: possible application to the eastern Tibetan margin

Pietro Sternai, Jean-Philippe Avouac, Laurent Jolivet, Claudio Faccenna, Taras Gerya, Thorsten W. Becker, Armel Menant

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Pietro Sternai, Jean-Philippe Avouac, Laurent Jolivet, Claudio Faccenna, Taras Gerya, et al. Sub-crustal forcing on the tectonic and topographic evolution of collision-subduction transition zones: possible application to the eastern Tibetan margin. EGU General Assembly 2016, 2016, Vienne, Austria. hal-03551947

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Submitted on 2 Feb 2022

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# Sub-crustal forcing on the tectonic and topographic evolution of collision-subduction transition zones: possible application to the eastern Tibetan margin

Pietro Sternai (1), Jean-Philippe Avouac (2), Laurent Jolivet (3), Claudio Faccenna (4), Taras Gerya (5), Thorsten W Becker (6), and Armel Menant (7)

(1) Division of Geology and Planetary Sciences, California Institute of Technology, Pasadena CA, USA; Now at University of Cambridge, Department of Earth Sciences, United Kingdom (pietrosternai@yahoo.it), (2) Division of Geology and Planetary Sciences, California Institute of Technology, Pasadena CA, USA, (3) Institute of Earth Sciences (ISTO) - University of Orléans, Orléans, France, (4) Department of Earth Sciences, University of Roma TRE, Rome, Italy, (5) Institute of Geophysics - Swiss Federal Institute of Technology (ETH), Zürich, Switzerland, (6) Department of Earth Sciences, University of Southern California, Los Angeles, USA, (7) Université d'Orléans, ISTO, UMR 7327, 45071 Orléans, France; Now at Université de Pau et des Pays de l'Adour, LFC-R, UMR 5150, Pau, France

The tectonic and topographic evolution of the eastern Tibetan margin is controlled by the India-Eurasia collision, gravitational collapse of the uplifted reaches and the dynamics of the Sunda and other western Pacific subduction zones, but their relative contributions remain elusive. Because crustal tectonics is the most serious contributor to the vertical ground motion and surface structures, previous models mostly focused on the partitioning between clock-wise rigid rotation or viscous eastward evacuation of the Eurasian crust in response to these driving mechanisms. Some authors further argued that large-scale mantle convection provides support to the topography of the Southeast Asia through vertical stresses and contribute to the overall India-Eurasia convergence. Minor attention, however, has been given to the potential forcing from the asthenospheric return flow owing to differential along-strike slab kinematics related to rollback and tearing of the Indian, Sunda and western Pacific slabs.

Here, we analyze 3D numerical geodynamic modeling results involving a collision-subduction system and show that vigorous asthenospheric flow due to differential along-strike slab kinematics may contribute to the surface strain and topography at the collision-subduction transition zone. We argue that protracted northward migration of the Indian slab and indentation front during south to south-westward rollback (late-Eocene to middle-Miocene) or stable (middle-Miocene to present) subduction along the Sunda and western Pacific margins may have produced a similar asthenospheric flow. This flow could have contributed to the Southeast Asia extrusion tectonics and uplift of the terrains around the eastern Himalayan syntaxaxis and protruding from southeast Tibet. Therefore, we suggest that the tectonics and topographic growth east and southeast of Tibet are controlled not only by crustal and lithospheric deformation but also by the asthenospheric dynamics.