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Li W.-H.,Key Laboratory of Earthprobe and Geodynamics | Li W.-H.,Chinese Academy of Geological Sciences | Gao R.,Key Laboratory of Earthprobe and Geodynamics | Gao R.,Chinese Academy of Geological Sciences | And 6 more authors.
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2014

The SinoProbe-02 North China joint seismic experiment consisted of three seismic recording efforts along 453 km long profile. The profile extended from the Huailai basin, across the Yinshan-Yanshan belt, Inner Mongolia paleo-uplift, Bainaimiao arc, Ondor Sum accretion complex to the Solonker suture zone. We processed, analyzed, and modeled the data collected during the wide-angle reflection and refraction effort. The seismic waves from 8 explosions were recorded by 300 Texan recorders. The P-wave field provided good quality data for most of the profile. Arrivals of refracted and reflected waves from sediments and basement (Pg), intracrustal phases (PcP, PlP), and the Moho (PmP, Pn) were typically observed. Hole's first arrival tomography program was used to obtain the upper crustal velocity structure. And Zelt's 2D travel time raytracing and inversion program (Rayinvr) was used to obtain the full crustal structure. The final 2D P-wave velocity model contains many features of tectonic significance: (1) The flat and relatively shallow Moho in the Central Asia Orogeny Belt (CAOB) may be attributed to the extension; thicker crust appears beneath the Yinshan-Yanshan belt and was probably generated by compression in the Jurassic-Cretaceous and modified during the later extension; (2) The velocity structure varies significantly from the NCC to the CAOB, and the boundary between them appears at the Chifeng-Bayan Obo fault; (3) Relatively high velocities in the upper crust of the middle part of the profile may represent the outcrop of large area granites; strong velocity variations beneath the Bainaimiao arc and Ondor Sum subduction accretion complex indicate that multiple pulses of magmatism occurred during the complex tectonic evolution of this area.

Lu Z.,Chinese Academy of Geological Sciences | Lu Z.,Key Laboratory of Earthprobe and Geodynamics | Gao R.,Chinese Academy of Geological Sciences | Gao R.,Key Laboratory of Earthprobe and Geodynamics | And 7 more authors.
Episodes | Year: 2015

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.

Gao R.,Chinese Academy of Geological Sciences | Gao R.,Key Laboratory of Earthprobe and Geodynamics | Chen C.,Cornell University | Lu Z.,Chinese Academy of Geological Sciences | And 8 more authors.
Tectonophysics | Year: 2013

From October 2009 to May 2010, through the support of the SinoProbe project a series of deep seismic reflection profiles were conducted. In order to image deep crustal structure of central Tibet, these profiles extend from the northern Lhasa terrane to the Qiangtang terrane by crossing the Bangong-Nujiang suture (BNS). The Moho depth varies from 75.1. km beneath the northmost Lhasa terrane to 68.9. km beneath southmost Qiangtang terrane. There is a 6.2. km sharp Moho offset across the BNS. Within 25. km to the north of the BNS, the Moho rises smoothly to 62.6. km. Distinct Moho reflector lies at 62.6-67.3. km beneath the Qiangtang terrane. The boundary of the middle and upper crusts and that between the middle and lower crusts interpreted from INDEPTH velocity model correspond to the strong reflection horizons at about18.8. km and 31.3. km depth beneath south Qiangtang terrane, respectively. A north-dipping series of reflection packages in the mid- to lower crust may mark subduction of the Lhasa terrane beneath the Qiantang terrane. The central portion of the reflection profile exhibits an antiformal structure at 14.1. km in the upper crust, which corresponds with the blueschist-bearing metamorphic belt. © 2013 The Authors.

Ye Z.,Chinese Academy of Geological Sciences | Ye Z.,Key Laboratory of Earthprobe and Geodynamics | Li Q.S.,Chinese Academy of Geological Sciences | Li Q.S.,Key Laboratory of Earthprobe and Geodynamics | And 10 more authors.
Science China Earth Sciences | Year: 2014

During Mesozoic to Cenozoic time, the large-scale tectono-magmatism had strongly modified the lithosphere beneath the southeastern continent of China, leaving the present-day lithosphere as a new one evolving from the ancient lithosphere that was largely removed and replaced. But this model proposed from geochemical and petrological research is urgently in need of support from seismic observational evidence. In this paper, based on the dataset recorded by the dense stations of two NE oriented broadband seismic profiles deployed in the coastal area of southeastern China (SE China), both P-wave (P-RF) and S-wave (S-RF) receiver functions were isolated. We identified Pls phase converted from the Lithosphere-Asthenosphere Boundary (LAB) in P-RFs of individual stations. Migrated Pls phase indicated a depth of 60–70 km for LAB. Inversions/ comparisons of P-RF (Pls phase) and S-RF (Slp phase) waveforms together with Ps and Sp imaging for the crust and upper mantle structure further confirmed this result. P-RF and S-RF migrated images exhibit that a flat LAB is positioned at the depth of 60–70 km spreading along the profile, whereas a distinct structural change of lithospheric base appears at the Min River estuary. Both Ps and PpPs migrated images of P-RFs present an abrupt Moho drop across the Min River fault from south to north, which is consistent with previous result obtained from deep seismic sounding. By taking into consideration other geological and geophysical features such as locally high anomalies of crustal Poisson’s ratios and heat flow at the Min River estuary, we infer that the Min River fault penetrates down to the Moho and may, furthermore, interfere in the deeper lithospheric structure. © 2014, Science China Press and Springer-Verlag Berlin Heidelberg.

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