IMPLICATIONS OF CRUSTAL PROPERTY VARIATIONS FOR MODELS OF TIBETAN PLATEAU EVOLUTION

Shear-coupled teleseismic P waves sampling the interior of the Tibetan plateau provide evidence of systematic variations in crustal structur e. The crust thins by up to 20 km from south to north with a concomita nt increase in Poisson's ratio from normal values in the south to unus ually high values in the north. This Suggests that the crust of the no rthern plateau is partially melted due to high temperatures. These cha nges imply spatial and perhaps temporal variations in the way the elev ation of the high plateau is created and maintained.