Seismic polarization anisotropy beneath the central Tibetan Plateau

Huang, Wei-Chuang; Ni, James; Tilmann, Frederik; Nelson, Douglas; Jingru, Guo; Zhao, Wenjin; Mechie, J.; Kind, R.; Saul, Joachim; Rapine, Richard; Hearn, Thomas M.

doi:10.1029/2000jb900339

Cited by 189 publications

(208 citation statements)

References 54 publications

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“…Shear wave splitting at stations located on the Tibetan Plateau and its margins has been studied extensively (e.g. McNamara et al 1994;Huang et al 2000;Flesch et al 2005;Lev et al 2006;Sol et al 2007;Wang et al 2008) and a wealth of data is now available to carry out the type of hypothesis testing described above. The two end-member models of asthenospheric flow and vertically coherent deformation were evaluated by Wang et al (2008), making use of nearly 200 splitting observations and 2000 GPS observations in a joint analysis.…”

Section: Tibetan Plateau and Surrounding Regionsmentioning

confidence: 99%

Shear Wave Splitting and Mantle Anisotropy: Measurements, Interpretations, and New Directions

2009

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Measurements of the splitting or birefringence of seismic shear waves that have passed through the Earth's mantle yield constraints on the strength and geometry of elastic anisotropy in various regions, including the upper mantle, the transition zone, and the D 00 layer. In turn, information about the occurrence and character of seismic anisotropy allows us to make inferences about the style and geometry of mantle flow because anisotropy is a direct consequence of deformational processes. While shear wave splitting is an unambiguous indicator of anisotropy, the fact that it is typically a near-vertical path-integrated measurement means that splitting measurements generally lack depth resolution. Because shear wave splitting yields some of the most direct constraints we have on mantle flow, however, understanding how to make and interpret splitting measurements correctly and how to relate them properly to mantle flow is of paramount importance to the study of mantle dynamics. In this paper, we review the state of the art and recent developments in the measurement and interpretation of shear wave splitting-including new measurement methodologies and forward and inverse modeling techniques,-provide an overview of data sets from different tectonic settings, show how they help us relate mantle flow to surface tectonics, and discuss new directions that should help to advance the shear wave splitting field.

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Section: Tibetan Plateau and Surrounding Regionsmentioning

confidence: 99%

Shear Wave Splitting and Mantle Anisotropy: Measurements, Interpretations, and New Directions

2009

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“…Both processes, the overthickening and the indentation, lead to a tectonic escape of material to the east under the squeeze of the N -S compression (Tapponnier, 1981(Tapponnier, , 1990Meissner et al, 2002). New arguments for the tectonic escape of central Tibet come from the strong SKS anisotropy (Huang et al, 2000;McNamara et al, 1994;Herquel et al, 1995).…”

Section: Introductionmentioning

confidence: 99%

“…During the active shooting phase, 11 large shots delivered seismic signals to the 62 seismometers, creating a dense network of overlapping travel time branches. Based on the seismic data of INDEPTH III, a number of papers were recently published: Huang et al (2000) report on the seismic anisotropy in central Tibet and its correlation to tectonics, based on teleseismic studies, and Zhao et al (2001) report on modeling the crustal structure in central Tibet from analyzing travel times from the 11 big shots along INDEPTH III. Rapine et al (2003) constrain the regional scale crustal structure in Tibet based on surface wave dispersion analysis; Haines et al (2003) concentrate on the shot-point data of INDEPTH III and deep crustal processes; and Kind et al (2002) present discontinuity images of the mantle, based on the migration of receiver functions and show that the Poisson ratio is almost normal in north central Tibet.…”

Section: Introductionmentioning

confidence: 99%

About the lithospheric structure of central Tibet, based on seismic data from the INDEPTH III profile

2004

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Signals from 11 shots and 8 earthquakes, and numerous teleseismic events were recorded along the 400-km seismic line INDEPTH III in central Tibet and interpreted together with previous seismic and tectonic data. The abnormal behavior of various mantle phases reveals a complex Moho-transition zone, especially in the northern part of the line, in the Changtang Block, where the lower crust and the mantle show unusually low velocities, a shingled appearance of P n and no low-velocity layer in the upper crust. The strong east -west anisotropy in the Changtang Block is related to an easterly escape movement of the whole lithosphere, facilitated by the warm and weak layers in the lower crust and the upper mantle, bounded apparently by two prominent west -east running fault zones. D

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“…Previous studies on seismic anisotropy (McNamara et al, 1994;Sol et al, 2007;Huang et al, 2000Huang et al, , 2007Wang et al, 2007Wang et al, , 2008Chen et al, 2013;Zhao et al, 2014;Guilbert et al, 1996;Bai et al, 2009) that compared splitting parameters with APM, GPS, and structural and topographical features provide crucial information concerning the dynamic deformation pattern and possible linkage of the strength of coupling between the crust and lithospheric mantle of the southeastern or eastern Tibetan region. We observe a sharp transition in the spatial distribution of φ s from nearly W-E in the western part of the study region to nearly NW-SE or NNW-SSE near the southeastern Tibetan margin (Fig.…”

Section: Deformation Pattern Revealed From the Comparison Of The Gpsmentioning

confidence: 99%

“…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%

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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Seismic polarization anisotropy beneath the central Tibetan Plateau

Cited by 189 publications

References 54 publications

Shear Wave Splitting and Mantle Anisotropy: Measurements, Interpretations, and New Directions

Shear Wave Splitting and Mantle Anisotropy: Measurements, Interpretations, and New Directions

About the lithospheric structure of central Tibet, based on seismic data from the INDEPTH III profile

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

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Seismic polarization anisotropy beneath the central Tibetan Plateau

Cited by 189 publications

References 54 publications

Shear Wave Splitting and Mantle Anisotropy: Measurements, Interpretations, and New Directions

Shear Wave Splitting and Mantle Anisotropy: Measurements, Interpretations, and New Directions

About the lithospheric structure of central Tibet, based on seismic data from the INDEPTH III profile

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

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