Crustal anisotropy from Moho converted Ps wave splitting analysis and geodynamic implications beneath the eastern margin of Tibet and surrounding regions

Chen, Yun; Zhang, Zhongjie; Sun, Chenguang; Badal, José

doi:10.1016/j.gr.2012.04.003

Cited by 141 publications

(113 citation statements)

References 63 publications

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“…The magma must have intruded through the whole lithosphere since the basalts have a sub-lithospheric mantle origin, and in some cases would become contaminated by lithospheric material, thus altering its composition (Wu and Zhang, 2012), and showing coupled features from the PmS and SKS splitting (Chen et al, 2013;Sun et al, 2013).…”

Section: Residual Gravity Anomaly and 3d Density Modelmentioning

confidence: 99%

Mantle origin of the Emeishan large igneous province (South China) from the analysis of residual gravity anomalies

Deng

Zhang

Mooney

et al. 2014

Lithos

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Section: Residual Gravity Anomaly and 3d Density Modelmentioning

confidence: 99%

Mantle origin of the Emeishan large igneous province (South China) from the analysis of residual gravity anomalies

Deng

Zhang

Mooney

et al. 2014

Lithos

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“…However, there exists significant azimuth difference of the fast polarization axes in the uppermost mantle layer (54-90 km) and the underlying layer (90-140 km) that has much lower shear rigidity. Our results indicate that there could exist large differences of shear wavespeed azimuthal anisotropy in the crust and upper mantle in SE Tibet, reflecting complicated deformation patterns in this region (e.g., Yao et al 2010;Yao 2012;Shi et al 2012;Sun et al 2012;Chen et al 2013). …”

Section: Inversion For Shear Wavespeeds and Azimuthal Anisotropymentioning

confidence: 82%

“…Modeling of receiver functions can give constraints on layered anisotropy in the crust (e.g., Ozacar and Zandt 2004;Levin et al 2008) although this approach is still very challenging in real practice. The Moho converted P m s phase splitting analysis from receiver functions can also provide constraints on average crustal azimuthal anisotropy, for instance, in SE Tibet (Xu et al 2006;Sun et al 2012;Chen et al 2013;Sun et al 2013). However, there still exists considerable inconsistency among these results.…”

Section: Discussionmentioning

confidence: 99%

“…However, there still exists considerable inconsistency among these results. For example, Chen et al (2013) and Sun et al (2013) found that the splitting time of the P m s wave is smaller than 0.3 s at most stations in SE Tibet. However, Sun et al (2012) used a more comprehensive analysis method and found 0.5-0.9 s splitting time of the P m s wave at a few stations in regions with thick crust in SE Tibet.…”

Section: Discussionmentioning

confidence: 99%

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A method for inversion of layered shear wavespeed azimuthal anisotropy from Rayleigh wave dispersion using the Neighborhood Algorithm

Yao

2015

Earthq Sci

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Seismic anisotropy provides important constraints on deformation patterns of Earth's material. Rayleigh wave dispersion data with azimuthal anisotropy can be used to invert for depth-dependent shear wavespeed azimuthal anisotropy, therefore reflecting depth-varying deformation patterns in the crust and upper mantle. In this study, we propose a two-step method that uses the Neighborhood Algorithm (NA) for the point-wise inversion of depth-dependent shear wavespeeds and azimuthal anisotropy from Rayleigh wave azimuthally anisotropic dispersion data. The first step employs the NA to estimate depthdependent V SV (or the elastic parameter L) as well as their uncertainties from the isotropic part Rayleigh wave dispersion data. In the second step, we first adopt a difference scheme to compute approximate Rayleigh-wave phase velocity sensitivity kernels to azimuthally anisotropic parameters with respect to the velocity model obtained in the first step. Then we perform the NA to estimate the azimuthally anisotropic parameters G c /L and G s /L at depths separately from the corresponding cosine and sine terms of the azimuthally anisotropic dispersion data. Finally, we compute the depth-dependent magnitude and fast polarization azimuth of shear wavespeed azimuthal anisotropy. The use of the global search NA and Bayesian analysis allows for more reliable estimates of depth-dependent shear wavespeeds and azimuthal anisotropy as well as their uncertainties.We illustrate the inversion method using the azimuthally anisotropic dispersion data in SE Tibet, where we find apparent changes of fast axes of shear wavespeed azimuthal anisotropy between the crust and uppermost mantle.

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“…Ozacar and Zandt (2004) have accounted for splitting of < 0.5 s over SKS split times due to the observed anisotropy of > 10 % in the crust. Splitting times of 0.2-0.3 s are observed within the eastern Tibet crust using splitting of the Moho-converted Ps phases (receiver functions, Chen et al, 2013). Tomographic (Huang et al, 2002(Huang et al, , 2009Hung et al, 2010;Yao et al, 2008Yao et al, , 2010Li et al, 2009), magnetotelluric (Bai et al, 2010), and gravity (Jordan and Watts, 2005) studies of the SE Tibetan region suggest ductile flow in the deeper region of the crust.…”

Section: Origin Of Anisotropy In the Southeastern Tibetan Regionmentioning

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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Crustal anisotropy from Moho converted Ps wave splitting analysis and geodynamic implications beneath the eastern margin of Tibet and surrounding regions

Cited by 141 publications

References 63 publications

Mantle origin of the Emeishan large igneous province (South China) from the analysis of residual gravity anomalies

Mantle origin of the Emeishan large igneous province (South China) from the analysis of residual gravity anomalies

A method for inversion of layered shear wavespeed azimuthal anisotropy from Rayleigh wave dispersion using the Neighborhood Algorithm

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

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Crustal anisotropy from Moho converted Ps wave splitting analysis and geodynamic implications beneath the eastern margin of Tibet and surrounding regions

Cited by 141 publications

References 63 publications

Mantle origin of the Emeishan large igneous province (South China) from the analysis of residual gravity anomalies

Mantle origin of the Emeishan large igneous province (South China) from the analysis of residual gravity anomalies

A method for inversion of layered shear wavespeed azimuthal anisotropy from Rayleigh wave dispersion using the Neighborhood Algorithm

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