Crustal structure of Gondwana- and Yangtze-typed blocks: An example by wide-angle seismic profile from Menglian to Malong in western Yunnan

Zhang, Zhongjie; Bai, Zhiming; Wang, Chunyong; Teng, Jun; Lü, Qingtian; Li, Jiliang; Sun, Shilong; Wang, Xinzheng

doi:10.1360/03yd0547

Cited by 36 publications

(24 citation statements)

References 3 publications

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“…Zhou et al (2001) studied the petrological structure of the crust and upper mantle using the DSS results and other field and experimental data in Yunnan. Recently, Wang (2003, 2004) and Zhang et al (2005) reanalyzed these DSS data, respectively. Through the seismic tomography of the travel-time data from Yunnan seismic network, Liu et al (1989), Chen et al (1990) and Wang et al (1994Wang et al ( , 2003 investigated the structure of the crust and uppermost mantle in Yunnan area, respectively.…”

Section: Geological Setting and Previous Geophysical Resultsmentioning

confidence: 99%

Crustal structure in Xiaojiang fault zone and its vicinity

et al. 2009

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Based on the integrative interpretation of travel-time data and amplitude information obtained from the deep seismic sounding experiment on the Chuxiong-Luoping profile, eastern Yunnan province, carried out in January of 2005, we present a 2-D P wave velocity structure along the profile. The crustal structure shows remarkable contrasts between the two sides of the Xiaojiang fault zone, although the whole profile is situated within the Yangtze platform. The average P wave velocities of the crust on the west and east sides of the fault zone are 6.21 km/s and 6.32 km/s, respectively, and the crustal thicknesses are 41 km and 45 km, respectively. These results imply that the crust to the east of the Xiaojiang fault zone presents characteristics of crustal structure in a stable platform, while the crust to the west is complicated with a lower velocity zone in middle of the upper crust. The average velocity of 6.21 km/s is lower than the global continental crustal average (6.30 km/s), indicating that the region is tectonically active. According to the lateral variation of velocity and depth of interfaces (including the Moho), it is inferred that the Xiaojiang fault zone has cut through the whole crust. It is also deduced that existence of low velocity zone in middle of the upper crust is conducive to the south-southeastern sliding of the SichuanYunnan (Chuan-Dian) rhombus block.

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Section: Geological Setting and Previous Geophysical Resultsmentioning

confidence: 99%

Crustal structure in Xiaojiang fault zone and its vicinity

et al. 2009

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“…The fast-wave direction of SKS splitting is not in accordance with the maximum shear direction of the surface deformation field. The crustal structure of Yunnan [32][33][34][35][36] reflects that the velocity distribution of lower crust is basically normal (6.6-6.8 km/s) except that there locally exists a low velocity zone in lower crust. Hence, we do not consider the decoupling of lower crust in the deformation analysis.…”

Section: Preliminary Analysis Of the Crustmantle Coupling And Decouplmentioning

confidence: 98%

Seismic anisotropy of upper mantle in eastern Tibetan Plateau and related crust-mantle coupling pattern

et al. 2007

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regional digital networks, and portable broadband seismic networks deployed in Sichuan, Yunnan and Tibet, we obtained the SKS fast-wave direction and the delay time between fast and slow waves of each station by use of the stacking analysis method, and finally acquired the fine image of upper mantle anisotropy in the eastern Tibetan Plateau and its adjacent regions. We analyzed the crust-mantle coupling deformation on the basis of combining the GPS observation results and the upper mantle anisotropy distribution in the study area. The Yunnan region out of the plateau has different features of crust-mantle deformation from the inside plateau. There exists a lateral transitional zone of crust-mantle coupling in the eastern edge of the Tibetan Plateau, which is located in the region between 26° and 27°N in the west of Sichuan and Yunnan. To the south of transitional zone, the fast-wave direction is gradually turned from S60°-70°E in southwestern Yunnan to near EW in southeastern Yunnan. To the north of transitional zone in northwestern Yunnan and the south of western Sichuan, the fast-wave direction is nearly NS. From crust to upper mantle, the geophysical parameters (e.g. the crustal thickness, the Bouguer gravity anomaly, and tectonic stress direction) show the feature of lateral variation in the transitional zone, although the fault trend on the ground surface is inconsistent with the fast-wave direction. This transitional zone is close by the eastern Himalayan syntaxis, and it may play an important role in the plate boundary dynamics.upper mantle anisotropy, SKS wave, fast-wave direction, crust-mantle coupling, lithospheric deformation Since the 1990s, the broadband digital technology has made great progress in the research of the Earth sciences. The seismograms recorded by the broadband seismometers deployed in the world are widely applied to the study of seismology, deep structure and geodynamics. In this paper, we focus on the mantle anisotropy and related geodynamic issues. Generally speaking, the mantle anisotropy is determined by the lattice-preferred orientation of olivine crystals as a result of the mantle deformation. There are various causes resulting in the mantle deformation. Among them, the plate motion is a direct cause. The size and direction of the mantle anisotropy strongly depend on the velocity of the plate motion. In the various subjects of recent studies on geodynamics, the anisotropy in the mantle is one of effective ways to probe the complicated deep structure beneath the continent and its evolution, the crust-mantle coupling deformation, etc. [1,2] .

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“…There exists a large variation of the thickness of anisotropic layer, which implies that the inside lithospheric deformation is asymmetrical beneath the study area. Other geophysical results show that the structures of the crust and upper mantle are obviously laterally inhomogenous [20][21][22][23] . According to the surface wave anisotropy beneath China continent, there exists a stronger anisotropy at the depth of 70-150 km [24] .…”

Section: Localization and Thickness Of Anisotropic Layermentioning

confidence: 99%

Seismic anisotropy of upper mantle in Sichuan and adjacent regions

Chang

Wang

Ding

2008

Sci. China Ser. D-Earth Sci.

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Based on the polarization analysis of teleseismic SKS waveform data recorded at 94 broadband seismic stations in Sichuan and adjacent regions, the SKS fast-wave direction and the delay time between the fast and slow shear waves were determined at each station using the grid searching method of minimum transverse energy and the stacking analysis method, and the image of upper mantle anisotropy was acquired. The fast-wave polarization directions are mainly NW-SE in the study area, NWW-SEE to its northeast and NS to its west. The delay time falls into the interval [0.47 s, 1.68 s]. The spatial variation of the fast-wave directions is similar to the variation of GPS velocity directions. The anisotropic image indicates that the regional tectonic stress field has resulted in deformation and flow of upper mantle material, and made the alignment of upper mantle peridotite lattice parallel to the direction of material deformation. The crust-upper mantle deformation in Sichuan and adjacent regions accords with the mode of vertically coherent deformation. In the eastern Tibetan Plateau, the crustal material was extruded to east or southeast due to SE traction force of the upper mantle material. The extrusion might be obstructed by a rigid block under the Sichuan Basin and the crust has been deformed. After a long-term accumulation of tectonic strain energy, the accumulative energy suddenly released in Yingxiu town of the Longmenshan region, and Wenchuan M S 8.0 earthquake occurred.

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Crustal structure of Gondwana- and Yangtze-typed blocks: An example by wide-angle seismic profile from Menglian to Malong in western Yunnan

Cited by 36 publications

References 3 publications

Crustal structure in Xiaojiang fault zone and its vicinity

Crustal structure in Xiaojiang fault zone and its vicinity

Seismic anisotropy of upper mantle in eastern Tibetan Plateau and related crust-mantle coupling pattern

Seismic anisotropy of upper mantle in Sichuan and adjacent regions

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