Shear-wave birefringence and current configuration of converging lithosphere under Tibet

Chen, Wang‐Ping; Martin, Michael W.; Tseng, Tai‐Lin; Nowack, Robert L.; Hung, S.; Huang, Bor‐Shouh

doi:10.1016/j.epsl.2010.04.017

Cited by 85 publications

(98 citation statements)

References 23 publications

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“…Our results contradict previous interpretations of an isotropic Indian lithospheric mantle (Chen and Ozalaybey, 1998;Barruol and Hoffmann, 1999;Chen et al, 2010) and add new constraints in understanding the types of deformation and their causes in the region.…”

Section: Introductioncontrasting

confidence: 56%

“…Splitting measurements from the Himalaya-Tibet collision zone have long been explained by the presence of a single homogeneous layer with a horizontal axis of symmetry (e.g. McNamara et al, 1994;Chen et al, 2010;Sol et al, 2007;Herquel et al, 1995;Hirn et al, 1995;Lavé et al, 1996;Sandvol et al, 1997;Huang et al, 2000;Lev et al, 2006;Wang et al, 2008;Fu et al, 2008;Sato et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

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Seismic anisotropy inferred from direct <i>S</i>-wave-derived splitting measurements and its geodynamic implications beneath southeastern Tibetan Plateau

et al. 2017

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Abstract. The present study deals with detecting seismic anisotropy parameters beneath southeastern Tibet near Namcha Barwa Mountain using the splitting of direct S waves. We employ the reference station technique to remove the effects of source-side anisotropy. Seismic anisotropy parameters, splitting time delays, and fast polarization directions are estimated through analyses of a total of 501 splitting measurements obtained from direct S waves from 25 earthquakes ( ≥ 5.5 magnitude) that were recorded at 42 stations of the Namcha Barwa seismic network. We observe a large variation in time delays ranging from 0.64 to 1.68 s, but in most cases, it is more than 1 s, which suggests a highly anisotropic lithospheric mantle in the region. A comparison between direct S-and SKS-derived splitting parameters shows a close similarity, although some discrepancies exist where null or negligible anisotropy has been reported earlier using SKS. The seismic stations with hitherto null or negligible anisotropy are now supplemented with new measurements with clear anisotropic signatures. Our analyses indicate a sharp change in lateral variations of fast polarization directions (FPDs) from consistent SSW-ENE or W-E to NW-SE direction at the southeastern edge of Tibet. Comparison of the FPDs with Global Positioning System (GPS) measurements, absolute plate motion (APM) directions, and surface geological features indicates that the observed anisotropy and hence inferred deformation patterns are not only due to asthenospheric dynamics but are a combination of lithospheric deformation and sub-lithospheric (asthenospheric) mantle dynamics. Direct S-wave-based station-averaged splitting measurements with increased back-azimuths tend to fill the coverage gaps left in SKS measurements.

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Section: Introductioncontrasting

confidence: 56%

Section: Introductionmentioning

confidence: 99%

Seismic anisotropy inferred from direct <i>S</i>-wave-derived splitting measurements and its geodynamic implications beneath southeastern Tibetan Plateau

et al. 2017

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“…Recent studies involving the comparison between GPS-observed plate motion and seismologically-observed anisotropy also support this idea (Xiong et al, 2003;Zhang et al, 2004;Wang et al, 2008). Shear-wave splitting measurement (Iidaka and Niu, 2001;Sol et al, 2007;Chen et al, 2010) was also compared with the P n anisotropy. In region c, the fast direction of P n anisotropy is generally the same as the SKS splitting fast direction.…”

Section: Resultsmentioning

confidence: 79%

P n tomographic velocity and anisotropy beneath the Tibetan Plateau and the adjacent regions

Liu

et al. 2011

Earth Planet Sp

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We present a tomographic velocity and anisotropy model of the uppermost mantle beneath the Tibetan Plateau and the adjacent regions. The investigation analyzed 105,385 P n phase readings from the International Seismological Centre (ISC) and the China Earthquake Data Center. The average P n velocity under the study area is approximately 8.15 km/s, with velocity perturbations up to 3-4%. We find high P n velocities under the Indian Plate and in the Tarim and Sichuan basins, low P n velocities under the Hindu Kush and in Myanmar and the adjacent region, and especially low P n velocities under the area north of the Indus-Yarlung Zangbo suture. The high P n velocity anomalies of the Indian Plate are discontinuous at the collision region in the east-west direction, indicating that the Indian Plate probably subducts in a piecewise manner. Distributions of P n velocities are used to validate mechanisms for the subduction of the Indian Plate presented in previous studies. In addition, P n anisotropy is obtained simultaneously with P n velocity. At plate collision zones, the fast P n anisotropy direction is parallel to the direction of the collision edge. We validate the existence of P n anisotropy under these regions and discuss the relationship of anisotropy with tectonic structure and plate movement.

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“…Many findings have been obtained using the data acquired during geophysical experiments conducted by the INDEPTH and Hi-CLIMB projects for studying the Tibetan Plateau (e.g., Kosarev et al 1999;Chen et al 2010;Kind et al 2002;Rapine et al 2003;Unsworth et al 2004;Zhang et al 2012). Teleseismic tomography has revealed a high-V zone beneath Tibet, south of the Bangong-Nujiang suture, which reflects the subducting Indian lithosphere .…”

Section: Tibetan Plateau and Southwest Chinamentioning

confidence: 97%

East Asia Structure and Tectonics

Zhao

2015

Multiscale Seismic Tomography

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In this chapter, we review seismic tomography studies of the East Asia region and new insights into plate deep subductions, continental seismotectonics, intraplate magmatism, and mantle dynamics. The subducting Pacific slab is stagnant in the mantle transition zone under the Korean Peninsula and East China, and a big mantle wedge (BMW) has formed above the stagnant slab. Hot and wet upwelling flows in the BMW have caused intraplate volcanoes in NE Asia, lithospheric thinning and reactivation of the North China Craton, and large earthquakes in and around East China. Deep earthquakes in the Pacific slab may be related to a metastable olivine wedge in the slab. The deepest earthquakes (~ 600 km depth) under NE Asia may release more fluids preserved in the slab to the overlying BMW, contributing to the Changbai volcanism. The descending Indian plate beneath the Tibetan Plateau is clearly revealed. The Hainan volcano in South China is a hotspot fed by a deep mantle plume associated with plate deep subductions in the east and the west.

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Shear-wave birefringence and current configuration of converging lithosphere under Tibet

Cited by 85 publications

References 23 publications

Seismic anisotropy inferred from direct <i>S</i>-wave-derived splitting measurements and its geodynamic implications beneath southeastern Tibetan Plateau

Seismic anisotropy inferred from direct <i>S</i>-wave-derived splitting measurements and its geodynamic implications beneath southeastern Tibetan Plateau

P n tomographic velocity and anisotropy beneath the Tibetan Plateau and the adjacent regions

East Asia Structure and Tectonics

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Shear-wave birefringence and current configuration of converging lithosphere under Tibet

Cited by 85 publications

References 23 publications

Seismic anisotropy inferred from direct &lt;i&gt;S&lt;/i&gt;-wave-derived splitting measurements and its geodynamic implications beneath southeastern Tibetan Plateau

Seismic anisotropy inferred from direct &lt;i&gt;S&lt;/i&gt;-wave-derived splitting measurements and its geodynamic implications beneath southeastern Tibetan Plateau

P n tomographic velocity and anisotropy beneath the Tibetan Plateau and the adjacent regions

East Asia Structure and Tectonics

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Product

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Seismic anisotropy inferred from direct <i>S</i>-wave-derived splitting measurements and its geodynamic implications beneath southeastern Tibetan Plateau

Seismic anisotropy inferred from direct <i>S</i>-wave-derived splitting measurements and its geodynamic implications beneath southeastern Tibetan Plateau