Complex images of Moho and variation of Vp/Vs across the Himalaya and South Tibet, from a joint receiver-function and wide-angle-reflection approach

A. Galve (1) , M. Sapin (1) , A. Hirn (1) , J. M. Díaz , J.-C. Lépine , M. Laigle (1) , J. Gallart , M. Jiang

1 IPGP - Institut de Physique du Globe de Paris

Teleseismic receiver functions (RF) allow us to image the spatial variation of the crust-mantle boundary (Moho) along a tight array spanning from south of the Himalayas to the centre of the Tibetan Plateau. This approach is cross- tested with wide-angle reflection imaging (WARR). Highlighted by each of the two independent methods, a complex architecture of the Moho with dipping and overlapping segments indicating lithospheric imbrication, is confirmed. The joint use of the two methods reveals an increase of the average crustal P-to-S-wave-velocity ratio from south to the centre of the Lhasa block. This may be due to lowered S-wave velocity confined in specific layers, that may be interpreted as partial melt. This accounts for half of the relative increase in the delay of direct teleseismic S-wave arrivals with respect to P-wave arrivals from south to north, suggesting a similar anomaly in the shallower mantle.

Domaines: Planète et Univers [physics]; Sciences de la Terre; Géophysique [physics.geo-ph]

A. Galve, M. Sapin, A. Hirn, J. M. Díaz, J.-C. Lépine, et al.. Complex images of Moho and variation of Vp/Vs across the Himalaya and South Tibet, from a joint receiver-function and wide-angle-reflection approach. Geophysical Research Letters, 2002, 29 (24), pp.35-1-35-4. ⟨10.1029/2002GL015611⟩. ⟨hal-02378690⟩