State Key Laboratory of Continental Tectonics and Dynamics

Beijing, China

State Key Laboratory of Continental Tectonics and Dynamics

Beijing, China
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Dechen S.,Chinese Academy of Geological Sciences | Dechen S.,State Key Laboratory of Continental Tectonics and Dynamics | van Loon A.J.T.,Adam Mickiewicz University | Aiping S.,Chinese Academy of Geological Sciences | Aiping S.,State Key Laboratory of Continental Tectonics and Dynamics
Journal of Palaeogeography | Year: 2013

A clastic dike containing unusually large clasts occurs in the Quaternary deposits that unconformably cover the Mesoproterozoic sediments in the Fangshan District, Beijing area, China. The material into which the dike intruded is also uncommon because it consists mainly of loess-type silts that were deposited by braided rivers. The intrusion of the dike is explained as the result of the expulsion of pore water into the coarse, gravel-containing layers of a braided river system. The large size of the clasts in the dike is explained by an exceptionally strong upwards-directed flow which owed its high energy to a high hydrostatic pressure that had been built up because pore water could not gradually seep through the impermeable silt-sized material during ongoing burial. This uncommon dike is compared with a second example, in similar Quaternary sediments covering the Mesozoic rocks in the Huairou District. © 2013 China University of Petroleum (Beijing)


Wu W.,State Key Laboratory of Continental Tectonics and Dynamics | Liu Q.-Y.,China Earthquake Administration | He R.-Z.,State Key Laboratory of Continental Tectonics and Dynamics | Qu Z.-D.,State Key Laboratory of Continental Tectonics and Dynamics
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2017

The Qiangtang basin is the largest Mesozoic-to-Cenozoic marine sediment basin in China. The central metamorphic belt in central Qiangtang divides it into South Qiangtang basin and North Qiangtang basin. This study conducted a series of teleseismic receiver functions across the Qiangtang basin. The teleseismic data came from a temporary seismic array in Qiangtang basin. High-quality receiver functions were picked up from 738 teleseismic traces of 338 teleseismic events recorded by 27 stations along 88.5°E in 2009-2010. 1-D S-wave velocity model was calculated by the nonlinear inversion of conjugate gradients algorithm for the complex spectrum ratios of receiver function. Because the method made full use of amplitude ratio between the vertical and radial components of the receiver function in time domain, the final model from the method is completely independent of the initial model parameters. The velocity model indicated that the Moho beneath Qiangtang area rises slowly from south to north. The South Qiangtang basin has an average Moho depth of 68 km. In the North Qiangtang basin the average Moho depth is 60 km, which are in accordance with H-κ stack and deep seismic reflection results. There is a continuous low velocity layer beneath the North Qiangtang basin. While in the South Qiangtang basin the low velocity area is discontinuous, which causes hot springs along thrust faults. The sedimentary thickness was determined by deep seismic reflection and Poisson's ratio. There is one large sedimentary basin in the South Qiangtang basin and two in the North. Geological survey suggested that the two depressions in North Qiangtang, Longwei Co and Baitan Lake, have pretty good outlook in petroleum exploration. © 2017, Science Press. All right reserved.


Lu H.,State Key Laboratory of Continental Tectonics and Dynamics | Lu H.,Chinese Academy of Geological Sciences | Wang E.,CAS Institute of Geology and Geophysics | Meng K.,CAS Institute of Geology and Geophysics
Tectonophysics | Year: 2014

Despite receiving considerable attention, the nature and timing of Cenozoic tectonic evolution of the Altyn Tagh Fault (AFT) remain highly debated. Here we conducted detailed magnetostratigraphy and anisotropy of magnetic susceptibility (AMS) studies on the Cenozoic Janggalsay section, southeast Tarim basin. Magnetostratigraphy indicates that the measured Janggalsay section spans a time interval of ~. 22-11. Ma. The magnetic declination data suggest that the Janggalsay site has rotated significantly counterclockwise (17.2°. ±. 8.5°) from ~. 22 to 17-15. Ma, while the rotation has terminated from 17-15 to 11. Ma. The results are consistent with a two-stage tectonic model for the ATF, with a phase of large magnitude strike-slip motion along the ATF from the Oligocene to Middle Miocene and a second phase of lower amounts of strike-slip motion and more widespread contraction since the Middle Miocene. The AMS fabric data and sedimentology of the Janggalsay section likely indicate the rapid rock uplift of the Altyn Tagh Range since 16. Ma. © 2014 Elsevier B.V.


Si J.,State Key Laboratory of Continental Tectonics and Dynamics | Si J.,Chinese Academy of Geological Sciences | Li H.,State Key Laboratory of Continental Tectonics and Dynamics | Li H.,Chinese Academy of Geological Sciences | And 6 more authors.
Tectonophysics | Year: 2014

The first hole of the Wenchuan earthquake Fault Scientific Drilling (WFSD-1) was started on Nov. 6, 2008 as a rapid response to the May 12, 2008 Wenchuan earthquake (Mw 7.9), which slipped along the Longmen Shan fault on the eastern margin of the Tibetan Plateau. WFSD-1 was drilled to a depth of 1201.15 m and intersected the presumed active fault zone at a depth of 590 m (FZ590), which contains the maximum value of fracture density and fresh fault gouge. Here we characterized fault rocks of FZ590 by conducting XRD analyses with cohesive and non-cohesive rock samples collected from WFSD-1 borehole cores. The results indicate that a clay anomaly zone is located in the FZ590 fault zone. The slight enrichment of smectite distributed in fresh fault gouge implies that there is a fault-related authigenic clay formation. In addition, the location of the slight enrichment of smectite is consistent with the plausible active slip zone determined by previous results, adding confidence to the supposition that the principal slip zone (PSZ) of the 2008 Wenchuan earthquake is located at a depth of 589.2. m and situated at the lithological boundary of the Neoproterozoic Pengguan Complex and Triassic Xujiahe Formation. The tiny clay anomaly signal captured from borehole cores implies that low frictional heat was generated by coseismic slip, which drives only slight authigenesis processes. Thus, other dynamic weakening mechanisms, such as thermal pressurization may be involved in the fault zone of the Yingxiu-Beichuan fault during 2008 Wenchuan earthquake. © 2013 Elsevier B.V.


Pan J.,State Key Laboratory of Continental Tectonics and Dynamics | Pan J.,Chinese Academy of Geological Sciences | Li H.,State Key Laboratory of Continental Tectonics and Dynamics | Li H.,Chinese Academy of Geological Sciences | And 8 more authors.
Tectonophysics | Year: 2014

On 12 May 2008, the Wenchuan earthquake (Mw 7.9) produced complicated thrust-type co-seismic surface rupture zones, which encompass the dextral-slip thrust of the Yingxiu-Beichuan fault, the approximately pure thrust of the Guanxian-Anxian fault, and the sinistral-slip thrust of the Xiaoyudong rupture zone located between the former two. In order to understand the faulting mechanism, we discuss the rupture process by examining the segmentation and kinematics of the surface rupture zones, together with the co-seismic fault striations at various sites. Based on the two along-strike main displacement peaks (6-6.5. m and 11-12. m) and on the different geometric and kinematic patterns for the southern and northern segments of the surface rupture zones, we find that the Wenchuan earthquake might have consisted of two rupture stages, which is in agreement with seismic wave inversion results. By comparing the kinematics of fault striations occurring in the Bajiaomiao and Beichuan areas, it suggests that during the first stage, thrusting along both the Yingxiu-Beichuan fault and Guanxian-Anxian fault produced the ~ 80-100. km-long Yingxiu-Qingping surface rupture segment and the ~ 80 km-long Guanxian-Anxian surface rupture zone, respectively. Then, faulting was triggered along the Yingxiu-Beichuan fault by the first rupture process, yielding the second rupture stage, which was characterized by dextral strike-slip (or dextral oblique thrusting). Due to the overlap between the two rupture stages, the southern segment (Yingxiu-Qingping) of the Yingxiu-Beichuan rupture zone comprises two different processes while the northern segment (Gaochuan-Beichuan-Shikan) only suggests one rupture phase. © 2013 Elsevier B.V.


Li H.,Chinese Academy of Geological Sciences | Li H.,State Key Laboratory of Continental Tectonics and Dynamics | Xu Z.,Chinese Academy of Geological Sciences | Xu Z.,State Key Laboratory of Continental Tectonics and Dynamics | And 15 more authors.
Tectonophysics | Year: 2014

The Wenchuan earthquake Fault Scientific Drilling project (WFSD) started right after the 2008 Mw 7.9 Wenchuan earthquake to investigate its faulting mechanism. Hole 1 (WFSD-1) reached the Yingxiu-Beichuan fault (YBF), and core samples were recovered from 32 to 1201.15. m-depth. Core investigation and a suite of geophysical downhole logs (including P-wave velocity, natural gamma ray, self-potential, resistivity, density, porosity, temperature, magnetic susceptibility and ultrasound borehole images) were acquired in WFSD-1. Integrated studies of cores and logs facilitate qualitative and quantitative comparison of the structures and physical properties of rocks. Logging data revealed that the geothermal gradient of the volcanic Pengguan complex (above 585.75 m) is 1.85 °C/100. m, while that of the sedimentary Xujiahe Formation (below 585.75 m) is 2.15 °C/100. m. In general, natural gamma ray, resistivity, density, porosity, P-wave velocity and magnetic susceptibility primarily depend on the rock lithology. All major fault zones are characterized by high magnetic susceptibility, low density and high porosity, with mostly low resistivity, high natural gamma ray and sound wave velocity. The high magnetic susceptibility values most likely result from the transformation of magnetic minerals by frictional heating due to the earthquake. The YBF exposed in WFSD-1 can be subdivided into five different parts based on different logging responses, each of them corresponding to certain fault-rocks. The high gamma radiation, porosity and P-wave velocity, as well as low resistivity and temperature anomalies indicate that the Wenchuan earthquake fault zone is located at 585.75-594.5. m-depth, with an average inclination and dip angle of N305° and 71°, respectively. The fact that the fracture directions in the hanging wall and footwall are different suggests that their stress field direction is completely different, implying that the upper Pengguan complex may not be local. © 2013 Elsevier B.V.


Wang H.,Chinese Academy of Geological Sciences | Wang H.,State Key Laboratory of Continental Tectonics and Dynamics | Li H.,Chinese Academy of Geological Sciences | Li H.,State Key Laboratory of Continental Tectonics and Dynamics | And 4 more authors.
Tectonophysics | Year: 2014

Fault zones record a series of faulting events that have occurred under different physical conditions during their evolution. Therefore, it is essential to understand the internal structures of fault zones in order to better understand the mechanical behavior of faults. The internal structure of the Wenchuan earthquake fault zone that prevailed at the Bajiaomiao outcrop and in the WFSD-1drilling cores, located along the southern segment of the Yingxiu-Beichuan surface rupture in the Hongkou area, is described in details in this paper. Based on field surveys, X-ray diffraction analysis, microstructure and analysis of the drilling cores, an ~. 240. m-wide fault zone was confirmed as the Yingxiu-Beichuan fault zone (YBF) at the Bajiaomiao outcrop, corresponding to the ~. 100. m fault zone in the WFSD-1 drilling cores. Fault rocks, including fault breccia, fault gouge and cataclasite were identified in both the outcrop and drilling cores, while pseudotachylyte was only present at the outcrop. Two different types of gouge veins, formed by thermal pressurization and fluidization respectively, are observed in this area. The YBF possesses the characteristics of a multiple core model, and consists of 5 different fault rock units. From top to bottom, these are cataclasite zone, black fault gouge-breccia zone, gray fault breccia zone, dark-gray fault breccia zone and black fault gouge-breccia zone. Outcrop investigation and drilling core research show that the slip zone of the Wenchuan earthquake does not completely follow the ancient fault slip zone. The Wenchuan earthquake fault is a high angle thrust fault which crosses the YBF obliquely. The multi-layered fault rocks displayed in the research area might indicate that the YBF comes from the long-term fault activity and evolution over the last ~ 15-10. Ma. © 2013 Elsevier B.V.


Wu C.,State Key Laboratory of Continental Tectonics and Dynamics | Wu C.,Chinese Academy of Geological Sciences | Li H.,State Key Laboratory of Continental Tectonics and Dynamics | Li H.,Chinese Academy of Geological Sciences | And 13 more authors.
Tectonophysics | Year: 2014

The inverse/right-lateral Yingxiu-Beichuan fault ruptured during the Wenchuan earthquake for ~ 270 km. We investigated the northeastern segment of that fault by analysing 3 newly acquired and 3 older seismic lines that cross the fault. We combine this analysis with that of the surface ruptures and of the regional geology in order to discuss the geometry, the style and the amount of motion of the fault. We conclude that the Yingxiu-Beichuan fault is very steep (~ 70°) at the surface and has still a dip > 45° at 6 km depth. The fault offsets all previous structures and particularly the Tangwangzhai nappes from which a vertical offset of 3 to 6. km is evaluated. The right-lateral component of motion along the Yingxiu-Beichuan fault appears to be larger at the surface than at depth and increases only slightly towards the NE. We suggest that the Yingxiu-Beichuan fault is continuous at depth between its northern and southern segments. © 2013 Elsevier B.V.


Dong H.,State Key Laboratory of Continental Tectonics and Dynamics | Xu Z.,Chinese Academy of Geological Sciences
Tectonophysics | Year: 2015


Qiao X.,State Key Laboratory of Continental Tectonics and Dynamics | Qiao X.,Chinese Academy of Geological Sciences | Guo X.,State Key Laboratory of Continental Tectonics and Dynamics | Guo X.,Chinese Academy of Geological Sciences
Acta Geologica Sinica | Year: 2013

The early Jurassic soft-sediment deformation occurring within lacustrine sandstone is distributed mainly in the Wuqia region of SW Tianshan Mountains, Xinjiang, western China. Triggered by earthquakes, such deformation was found to occur in three beds overlying the lower Jurassic Kangsu Formation. The main styles of deformation structures comprise load cast, ball-and- pillow, droplet, cusps, homogeneous layer, and liquefied unconformity. The deformation layers reflect a series of three strong earthquakes at the end of early Jurassic in the Wuqia region. The differences of deformation mechanisms undergone might represent the varying magnitudes of the earthquake events. During the early Jurassic, the Wuqia region was located in a pull-apart basin controlled by the significant Talas-Ferghana strike-slip fault in central Asia, which initiated the soft-sediment deformation induced by earthquakes. Our research suggests that the paleoseismic magnitudes could have ranged from Ms 6.5 to 7.

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