Research

    Active Continental Deformation in the India-Asia Collision zone

Seismicity and topography  suggest that the 4-5 cm/yr northward indentation of India induces deformation distributed throughout central Asia . As suggested from the analysis of fault geometry and style by P. Tapponnier and P. Molnar in the late 70’s deformation is partioned between crustal thickening and extrusion of Tibet . Base on early estimates of fault slip rates on some of the major faults in central Asia , we have derived a simple block model of active deformation [Avouac and Tapponnier, 1993].

Some of the slip rates used in this model have been better constrained since then (cf IPGP/Tectonique web site, or Lavé and Avouac [2000]) but it seems clear that the main feature of the model is a robust result: part of northward motion of India is accommodated by northward extrusion of Tibet which is transferred to eastward extrusion of south China (See fig 1).

                            Figure 1 - Kinematic block model of active deformation in central Asia

 GPS results are consistent to the first order with this kinematics (See fig 2 ) compilation by Cecile Lasserre). It should be noticed that although the detail of the kinematics is not well constrained, about a third to half of the northward motion of India is absorbed by localized thrusting along the Himalaya . There is no doubt that a significant fraction of the deformation is localized on a few major faults which are also the main concern in terms of seismic hazard.

Figure 2 - Velocities relative to Eurasia measured from GPS

  My main contributions on the subject:

Avouac, J.P., and P. Tapponnier, Kinematic model of active deformation in central Asia, Geophys. Res. Let., 20, 895-898, 1993.   [PDF]

Avouac, J.P., P. Tapponnier, M. Bai, H. You and G. Wang, Active thrusting and folding along the northeastern Tien Shan and late Cenozoic rotation of Tarim with respect to Dzungaria and Kazakhstan, J. Geophys. Res., 98, 6755-6804, 1993.  

Lavé, J., J.P. Avouac, R. Lacassin, P. Tapponnier and J.P. Montagner, Seismic anisotropy beneath Tibet: evidence for eastward extrusion of the tibetan lithosphere? Earth, Planet. Sc. Let., 140, 83-96, 1996.   [PDF]