Variation of Moho Depth across Bangong-Nujiang Suture in Central Tibet—Results from Deep Seismic Reflection Data

Zhanwu Lu,Xiaosong Xiong,Rui Gao,Wenhui Li,Hongqiang Li

doi:10.4236/ijg.2015.68066

Abstract

There is a long-term dispute at Moho depth across the Bangong-Nujiang suture (BNS). Due to the complicated and changeable seismic geological condition, it is not easy to acquire images of the reflective Moho in central Tibet. In the support of the SinoProbe project, a series of deep seismic reflection profiles were conducted to image Moho structure across the BNS and the Qiangtang terrane. These profiles extend from the northern Lhasa terrane to the Qiangtang terrane crossing the BNS. Both shot gathers and migration data show clear Moho images beneath the BNS. The Moho depth varies from 75.1 km (~24 s TWT) beneath the northmost Lhasa terrane to 68.9 km (~22 s TWT) beneath southmost Qiangtang terrane, and rises smoothly to 62.6 km (~20 s TWT ) at ~28 km north of the BNS beneath the Qiangtang terrane. We speculate that the Moho appears a 6.2 km sharp offset across the BNS and becomes ~12.5 km shallower from the northmost Lhasa terrane to the south Qiangtang terrane at ~28 km north of the BNS. The viewpoint of Moho depth across the BNS based on deep seismic reflection data is inconsistent with the previous 20 km offset.

Highlights

IntroductionThough the Bangong-Nujiang suture (BNS) and Qiangtang terrane area in central Tibet are usually considered
Though the Bangong-Nujiang suture (BNS) and Qiangtang terrane area in central Tibet are usually consideredHow to cite this paper: Lu, Z.W., Gao, R., Li, H.Q., Li, W.H. and Xiong, X.S. (2015) Variation of Moho Depth across Bangong-Nujiang Suture in Central Tibet—Results from Deep Seismic Reflection Data
P-wave velocity structure showed that the Indian lithospheric mantle had subducted beneath central Tibet and that its frontier had passed through the BNS and extended northward beneath the Qiangtang Terrane at latitude 34 ̊N [6]

Summary

Introduction

Though the Bangong-Nujiang suture (BNS) and Qiangtang terrane area in central Tibet are usually considered. A lot of deep seismic profiling projects have provided a great number of seismic lines that image the structure of the continental crust and the crust-mantle boundary [11]-[15] This approach was proved to be successful in studying the tectonic development of southern Tibet in the early 1990s [16]-[18]. To test the acquisition technique for detecting the Moho structure in central Tibet, SinoProbe Project performs a deep seismic reflection profile, which starts west of Selin Co in the northern Lhasa terrane, crosses the Bangong Nujiang Suture (BNS) to the west of Lunpola, skirts the eastern extension of the central Qiantang anticline and ends at Dogai Coring just to the south of the Jinsha Suture (JS). We just report the single shot records of 1000 kg explosive and migration section across the BNS (Figure 1)

Geological Setting

Deep Seismic Reflection Data Acquisition

Results

Discussion

Conclusion