Seismic evidence for stepwise thickening of the crust across the NE Tibetan plateau

We performed a receiver function analysis on teleseismic data recorded along two 550 km-long profiles crossing the northeastern Tibetan plateau. Results from time to depth migration, grid-search V-p/V-s determination and simulated annealing inversion of waveforms, reveal that the crust thickens from similar to50 kin near the northern edge of the plateau to similar to80 km south of the Jinsha suture in the Qiang Tang block. Crustal thickening occurs in staircase fashion with steps located beneath the main, reactivated sutures. The V-p/V-s ratio, close to the global continental average does not suggest widespread partial melting but rather a more usual separation between an upper felsic and a lower mafic part within the northeastern Tibetan crust. (C) 2002 Elsevier Science B.V. All rights reserved.