Surface wave dispersion across Tibet: Direct evidence for radial anisotropy in the crust

Duret, F.; Shapiro, N. M.; Cao, Zeng; Levin, Vadim; Molnár, Péter; Roecker, S. W.

doi:10.1029/2010gl043811

Cited by 36 publications

(37 citation statements)

References 31 publications

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“…Subsequently, Duret et al . [] presented evidence from individual seismograms using aftershocks of the Wenchuan earthquake of 12 May 2008 that the Rayleigh‐Love discrepancy is so significant for paths crossing Tibet that crustal radial anisotropy probably also extends into eastern Tibet. Huang et al .…”

Section: Introductionmentioning

confidence: 99%

Crustal radial anisotropy across Eastern Tibet and the Western Yangtze Craton

et al. 2013

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[1] Phase velocities across eastern Tibet and surrounding regions are mapped using Rayleigh (8-65 s) and Love (8-44 s) wave ambient noise tomography based on data from more than 400 Program for Array Seismic Studies of the Continental Lithosphere and Chinese Earthquake Array stations. A Bayesian Monte Carlo inversion method is applied to generate 3-D distributions of Vsh and Vsv in the crust and uppermost mantle from which radial anisotropy and isotropic Vs are estimated. Each distribution is summarized with a mean and standard deviation, but is also used to identify "highly probable" structural attributes, which include (1) positive midcrustal radial anisotropy (Vsh > Vsv) across eastern Tibet (spatial average = 4.8% ± 1.4%) that terminates abruptly near the border of the high plateau, (2) weaker (À1.0% ± 1.4%) negative radial anisotropy (Vsh < Vsv) in the shallow crust mostly in the Songpan-Ganzi terrane, (3) negative midcrustal anisotropy (À2.8% ± 0.9%) in the Longmenshan region, (4) positive midcrustal radial anisotropy (5.4% ± 1.4%) beneath the Sichuan Basin, and (5) low Vs in the middle crust (3.427 ± 0.050 km/s) of eastern Tibet. Midcrustal Vs < 3.4 km/s (perhaps consistent with partial melt) is highly probable only for three distinct regions: the northern Songpan-Ganzi, the northern Chuandian, and part of the Qiangtang terranes. Midcrustal anisotropy provides evidence for sheet silicates (micas) aligned by deformation with a shallowly dipping foliation plane beneath Tibet and the Sichuan Basin and a steeply dipping or subvertical foliation plane in the Longmenshan region. Near vertical cracks or faults are believed to cause the negative anisotropy in the shallow crust underlying Tibet.

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Section: Introductionmentioning

confidence: 99%

Crustal radial anisotropy across Eastern Tibet and the Western Yangtze Craton

et al. 2013

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“…Strong azimuthal anisotropy in the upper crust is observed in South Africa and has been related to extension at the southern tip of the African Rift (Adam and Lebedev, 2012). Midcrustal strong radial anisotropy has been observed in Tibet (Duret et al, 2010;Shapiro et al, 2004), whereas radial anisotropy has been inferred in the lower crust in the Aegean Sea (Endrun et al, 2008(Endrun et al, , 2011 and azimuthal anisotropy in the lower crust of the western United States (Lin et al, 2011).…”

Section: Crustal Anisotropymentioning

confidence: 94%

“…Larger values of x $ 1.18 (Debayle and Kennett, 2000;Maupin and Cara, 1992) are challenging to reconcile with olivine LPO and may require additional fine-horizontal layering. Large Rayleigh-Love discrepancies, with fast Love waves, are not limited to waves sensitive to the uppermost mantle, but have also been found at periods sensitive to the crust in tectonic regions, such as Tibet (Duret et al, 2010) and the Aegean Sea (Endrun et al, 2008).…”

Section: Surface Waves and Upper Mantlementioning

confidence: 98%

Theory and Observations - Seismic Anisotropy

Maupin

Park

2015

Treatise on Geophysics

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“…Clark et al () suggested the presence of crustal flow in the NE Tibetan plateau via fitting the observed northeastward sloping topography by inducing an underlying lower crustal channel with a thickness of 15 km. Recent geophysical observations offer several lines of evidence, such as low velocity zone (Bao et al, ; Schoenbohm et al, ; Yang et al, ) and strong radial anisotropy (Duret et al, ; Li et al, ; Shapiro et al, ; Xie et al, ) in the middle and/or lower crust, in support of the existence of crustal flow in this region. However, the low and moderate Poisson's ratio (Wang et al, ; Xu et al, ) indicated a generally felsic crust in this region, which is contradictory to the mafic crustal composition predicted by the lower crustal flow model (Pan & Niu, ).…”

Section: Introductionmentioning

confidence: 95%

Lithospheric SH Wave Velocity Structure Beneath the Northeastern Tibetan Plateau From Love Wave Tomography

Xiao

2019

JGR Solid Earth

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The northeastern (NE) Tibetan plateau has been a prime site to understand the dynamic processes responsible for the rise and lateral growth of the Tibetan plateau. Here we construct a high‐resolution lithospheric scale isotropic SH wave velocity model (down to the depth of 130 km) for the NE Tibetan plateau and its adjacent regions based on the measurements of fundamental‐mode Love wave dispersions (20–100 s) with seismic data recorded by ChinArray II and China Digital Seismic Array using two‐plane wave method. Prominent slow SH wave velocity (VSH) is observed in the midlower crust of the NE Tibetan plateau, specifically in the Qilian Orogenic Belt and the Songpan‐Ganzi Terrane regions, coincident with previously indicated significantly slow SV wave velocity (VSV), probably implying the existence of partial melts in the midlower crust. This low SH wave velocity anomaly could be traced down to the uppermost mantle, indicating a weak and warm lithosphere, which we interpret as a consequence of asthenosphere upwelling after lithospheric mantle removal in the NE Tibetan plateau. The asthenosphere upwelling and associated deep‐seated thermal buoyancy could explain the occurrence of partial melting in the mid‐lower crust and account for parts of high elevations in the NE Tibetan plateau. The western Qinling orogenic belt is characterized with a high velocity anomaly in most of lithosphere, which is inconsistent with the existence of channel flow within the lithosphere along the Qinling orogenic belt from the Tibetan plateau.

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Surface wave dispersion across Tibet: Direct evidence for radial anisotropy in the crust

Cited by 36 publications

References 31 publications

Crustal radial anisotropy across Eastern Tibet and the Western Yangtze Craton

Crustal radial anisotropy across Eastern Tibet and the Western Yangtze Craton

Theory and Observations - Seismic Anisotropy

Lithospheric SH Wave Velocity Structure Beneath the Northeastern Tibetan Plateau From Love Wave Tomography

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