Seismic Anisotropy of Upper Mantle in the Northeastern Margin of the Tibetan Plateau

Chang, Ling; Wang, Chunyong; Ding, Zhongli; Mei, Zhou; Yang, Jiansi; Xu, Zhiqiang; Jiang, Xudong; Zheng, Xiaojing

doi:10.1002/cjg2.1220

Cited by 31 publications

(41 citation statements)

References 20 publications

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“…The results of the rest stations were published [15][16][17] , where we re-measure the results at some stations that have new seismic records. Figure 5 shows the scatter of shear-wave splitting parameters by stations.…”

Section: Results Of Sks Splitting Measurement and Analysismentioning

confidence: 99%

“…Hence, we can infer kinematic models of the medium of the earth's interior [17] . For stable continental regions, it is interpreted as "fossil" anisotropy, whereas the anisotropy reflects present-day tectonic activities in tectonic active continental regions.…”

Section: Causes Of Anisotropymentioning

confidence: 99%

“…The SKS wave splitting results were obtained at some seismic stations in Sichuan and adjacent regions [15][16][17] , but there are no more broadband seismic stations. Up to now, 52 broadband seismic stations have been deployed and operated in Sichuan, with relatively even station distribution and high data quality, facilitating the studies on the upper mantle anisotropy.…”

mentioning

confidence: 95%

“…Many anisotropic studies have been done that are related to the mantle deformation beneath the Tibetan plateau, and carried out a lot of relevant anisotropic studies [11][12][13][14][15][16][17] . The SKS wave splitting results were obtained at some seismic stations in Sichuan and adjacent regions [15][16][17] , but there are no more broadband seismic stations.…”

mentioning

confidence: 99%

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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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Section: Results Of Sks Splitting Measurement and Analysismentioning

confidence: 99%

Section: Causes Of Anisotropymentioning

confidence: 99%

mentioning

confidence: 95%

mentioning

confidence: 99%

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Seismic anisotropy of upper mantle in Sichuan and adjacent regions

Chang

Wang

Ding

2008

Sci. China Ser. D-Earth Sci.

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“…A few important results [7][8][9][10][11][12][13] on the upper mantle anisotropy have been achieved in Chinese mainland (especially, the Tibetan Plateau and adjacent regions). In eastern China, Luo et al [14] presented anisotropic results at 17 stations.…”

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confidence: 99%

Seismic anisotropy of upper mantle in eastern China

Chang

Wang

Ding

2009

Sci. China Ser. D-Earth Sci.

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Based on the polarization analysis of teleseismic SKS waveform data recorded at 65 seismic stations which respectively involved in the permanent and temporary broadband seismograph networks deployed in eastern China, the SKS fast-wave direction and the delay time between the fast and slow shear waves at each station were determined by use of SC method and the stacking analysis method, and then the image of upper mantle anisotropy in eastern China was acquired. In the study region, from south to north, the fast-wave polarization directions are basically EW in South China, gradually clockwise rotate to NWW-SEE in North China, then to NW-SE in Northeast China. The delay time falls into the interval [0.41 s, 1.52 s]. Anisotropic characteristics in eastern China indicate that the upper mantle anisotropy is possibly caused by both the collision between the Indian and Eurasian Plates and the subduction from the Pacific and Philippine Sea Plates to the Eurasian Plate. The collision between two plates made the crust of western China thickening and uplifting and the material eastwards extruding, and then caused the upper mantle flow eastwards and southeastwards. The subduction of Pacific Plate and Philippine Sea Plate has resulted in the lithosphere and the asthenosphere deformation in eastern China, and made the alignment of upper mantle peridotite lattice parallel to the deformation direction. The fast-wave polarization direction is consistent with the direction of lithosphere extension and the GPS velocity direction, implying that the crust-upper mantle deformation is possibly a vertically coherent deformation. eastern China, upper mantle anisotropy, SKS wave, fast-wave direction, lithosphere deformationSeismic anisotropy is an effective method for understanding the crust and upper mantle deformation. The anisotropy can be used to understand the intraplate deformation features and the deformation status of lithosphere mantle related to the plate tectonic movements. Recent researches show that the mantle anisotropy is a consequence of strain-induced lattice preferred orientation of olivine crystals [1,2] . There are several 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. Based on the assumption of plate driving force, two kinematics models of crust-mantle deformation have been proposed recently, i.e., the vertically coherent deformation [3,4] and the simple asthenospheric flow [5] . The former predicts that the plates strongly have been coupled with the mantle and driven by the flow field generated from density heterogeneity in the mantle. The latter reflects that the plates are self-driven and decoupled from the mantle by mechanically weak asthenosphere, and the mantle deformation is attributed to the difference between the top and the bottom velocities in asthenosphere. In the various subjects of recent studies on geodynamics, the mantle anisotropy is one of the effective mea...

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A Study of Seismic Anisotropy of Wenchuan Earthquake Sequence

Gao

Zhao

Yao

et al. 2009

Chinese J of Geophysics

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Using aftershock data of the 2008 Wenchuan earthquake, recorded by seismic stations in the seismic source area and around, with the systematic analysis method (SAM) of shear‐waves splitting, this paper analyzes the anisotropic characteristics in the crust along the Longmenshan fault belt where the Wenchuan earthquake occurred and obtains the directions of the principal compressive stress field in the crust and its spatial distributions. The results show spatial differences: plotting a boundary approximately in Anxian area in the middle of Longmenshan fault belt, the polarization directions of fast shear‐waves at stations located at the northeast segment of Longmenshan fault belt are at NE direction, consistent with the strike of the faults. However, the polarization directions of fast shear‐waves at stations located at the southwest segment are at NW direction, perpendicular to the strike of the faults. This pattern also indicates that the southwest segment of the Longmenshan faults are mainly in thrust fault and the northeast segment are of obviously strike‐slip component. In this study, the polarization directions of fast shear‐waves are scattered at stations near the intersection area of the Longmenshan faults, the Xianshuihe faults and the Anninghe–Xiaojiang faults. It is possibly attributed to the local complex geological tectonics around the seismic source area, consistent with the characteristics of the complex direction of the principal compressive stress in this zone.

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Seismic Anisotropy of Upper Mantle in the Northeastern Margin of the Tibetan Plateau

Cited by 31 publications

References 20 publications

Seismic anisotropy of upper mantle in Sichuan and adjacent regions

Seismic anisotropy of upper mantle in Sichuan and adjacent regions

Seismic anisotropy of upper mantle in eastern China

A Study of Seismic Anisotropy of Wenchuan Earthquake Sequence

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