Evidence for mechanical coupling and strong Indian lower crust beneath southern Tibet

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How surface deformation within mountain ranges relates to tectonic processes at depth is not well understood. The upper crust of the Tibetan Plateau is generally thought to be poorly coupled to the underthrusting Indian crust because of an intervening low-viscosity channel1. Here, however, we show that the contrast in tectonic regime between primarily strike-slip faulting in northern Tibet and dominantly normal faulting in southern Tibet requires mechanical coupling between the upper crust of southern Tibet and the underthrusting Indian crust. Such coupling is inconsistent with the presence of active ‘channel flow’ beneath southern Tibet, and suggests that the Indian crust retains its strength as it underthrusts the plateau. These results shed new light on the debates regarding the mechanical properties of the continental lithosphere2,3,4, and the deformation of Tibet1,5,6,7,8,9,10.

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Figure 1: Tectonic regime within and around the Tibetan Plateau.
Figure 2: Modelled principal axes of the horizontal strain-rate tensor at the surface.


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We thank the Gordon and Betty Moore Foundation for support through the Caltech Tectonics Observatory, and Pembroke College in the University of Cambridge for financial support to A.C. This work benefited from a review by L. Flesch. This is Caltech Tectonics Observatory contribution number 145.

Author information

A.C. performed the calculations, A.C., J.-P.A. and B.W. discussed the results, and A.C. and J.-P.A. wrote the manuscript.

Correspondence to Alex Copley.

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The authors declare no competing financial interests.

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This file contains Supplementary Figures 1-3 with legends and Supplementary References for the earthquake focal mechanisms show in black in Figure 1 of the main paper. (PDF 2509 kb)

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Copley, A., Avouac, J. & Wernicke, B. Evidence for mechanical coupling and strong Indian lower crust beneath southern Tibet. Nature 472, 79–81 (2011) doi:10.1038/nature09926

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