LARGE-SCALE DEFORMATION IN THE INDIA-ASIA COLLISION CONSTRAINED BY EARTHQUAKES AND TOPOGRAPHY

We show, using earthquake and topographic data, that deformation in the India-Asia collision is partitioned between domains of lower crustal flow and regions deforming as Mohr-Coulomb wedges. Analysis of earthquake focal mechanisms allows division of the India-Asia collision into kinematic domains that strongly correlate with topography. These kinematic domains indicate extreme strain partitioning dominated by oblique slip deformation. The Kunlun and South Tibetan fault systems mark discontinuities in the strain field and bound a region of high, flat topography which deforms by transtension. The margins of the orogen deform by transpression or compression and are topographically rough. Seismicity and topography correlate due to MohrCoulomb wedge mechanics at the plateau margins, whereas the flat interior of the Tibetan plateau is underlain by viscous lower crust.