Large explosive shot gathers along the SinoProbe deep seismic reflection profile and Moho depth beneath the Qiangtang terrane in central Tibet

Abstract

Owing to extreme topography, rapid velocity and thickness variation of near-surface layer and strong seismic attenuation through the thickest crust of the Earth, it is not easy to acquire reflective Moho in central Tibet. However, with help from the SinoProbe deep seismic reflection experiment, large explosive of 1000 kg seismic sources have been tentatively detonated in the Qiangtang terrane and good quality data were acquired. Compared with multifold data, the single-fold record from single shot gather can also show clear Moho image in the Qiangtang terrane. Moho reflection appears at ∼ 24 s TWT (∼ 75.1 km) in the northernmost Lhasa terrane and at about 21 ∼ 20 s TWT (65.7 - 62.6 km) beneath the Qiangtang terrane. We speculate that Moho gets 9.4 km-12.5 km shallower from the Lhasa to the Qiangtang terrane rather than a 20 km offset. There is no obvious change of Moho depth across the Shung Hu suture.