Crustal structure and deformation under the Longmenshan and its surroundings revealed by receiver function data

Sun, Yanan; Liu, Jianxin; Zhou, Keping; Chen, Bo; Guo, Ren

doi:10.1016/j.pepi.2015.04.005

Cited by 42 publications

(49 citation statements)

References 72 publications

(118 reference statements)

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“…As discussed above, the δ t measured using the P m s phase is mainly from the mid‐lower crust. Crustal V p / V s studies (Chen et al, ; Sun et al, , ; C. ‐Y. Wang et al, ) revealed that this area is dominated by higher than average V p / V s values, and magnetotelluric observations (e.g., Bai et al, ) showed a high electrical conductivity at lower crust depth beneath this area.…”

Section: Discussionmentioning

confidence: 92%

“…Relative to the other segments of the LMS fault zone, the northern segment has low V p / V s values (ranging from 1.68 to 1.74; Sun et al, ), suggesting the absence of crustal flow. The consistency between the ϕ measurements and the direction of the maximum horizontal compression (Figure ), which is fault‐orthogonal, suggests that NW‐SE oriented extensional cracks are mostly responsible for the observed anisotropy.…”

Section: Discussionmentioning

confidence: 99%

“…Sun et al () used a harmonic analysis method to suggest that crustal anisotropy has an important contribution to XKS splitting. Sun et al () speculated that uplifting of the LMS fault zone was the result of lower crustal flow extrusion and supported a coupled deformation model from the lower crust to upper mantle underneath the LMS fault zone. Kong et al () utilized moveout time variations of the P m s phase to suggest that crustal thickening is the main mechanism of the high topographic gradient across the LMS Fault, a conclusion that is inconsistent with that from Sun et al ().…”

Section: Introductionmentioning

confidence: 94%

“…It has long been recognized that seismic azimuthal anisotropy can provide important insights into the strain occurring at depth (Crampin et al, 1980;Lev et al, 2006;Mainprice & Nicolas, 1989), and thus can provide (Gan et al, 2007) with respect to the stable Eurasia, and the thick black arrows represent the APM derived from the GSRM-APM-1 model (Kreemer, 2009). The red bars show previous crustal anisotropy measurements (Chen et al, 2013;Kong et al, 2016;Sun et al, 2015), and the thin gray bars are XKS splitting results obtained from http://splitting.gm.univ-montp2.fr/DB/public/searchdatabase.html. The solid red rectangle in the inset map indicates the location of the study area.…”

Section: Introductionmentioning

confidence: 99%

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Crustal Azimuthal Anisotropy Beneath the Southeastern Tibetan Plateau and its Geodynamic Implications

et al. 2018

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The fast orientation and magnitude of crustal azimuthal anisotropy beneath the southeastern Tibetan Plateau and adjacent areas are measured by analyzing the sinusoidal moveout of the P to S converted phase from the Moho. Beneath the tectonically active plateau, the mean magnitude is 0.48 ± 0.13 s, which is about twice as large as that observed in the stable Sichuan Basin (0.23 ± 0.10 s). The two areas are separated by the Longmenshan fault zone, a zone of devastating earthquakes including the 12 May 2008 MW 7.9 Wenchuan earthquake. Fault orthogonal fast orientations observed in the southern Longmenshan fault zone, where previous studies have revealed high crustal Vp/Vs and suggested the presence of mid‐lower crustal flow, may reflect flow‐induced lattice preferred orientation of anisotropic minerals. Fault parallel anisotropy in the central segment of the fault zone is most likely related to fluid filled fractures, and fault perpendicular extensional cracks are probably responsible for the observed anisotropy in the northern segment. The crustal anisotropy measurements, when combined with results from previous studies, suggest the existence of mid‐lower crustal flow beneath the southeastern margin of the plateau. Comparison of crustal anisotropy obtained before and after the Wenchuan earthquake suggests that the earthquake has limited influence on whole crustal anisotropy, although temporal changes of anisotropy associated with the earthquake have been reported using splitting of shear waves from local earthquakes occurred in the upper crust.

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Section: Discussionmentioning

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

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Crustal Azimuthal Anisotropy Beneath the Southeastern Tibetan Plateau and its Geodynamic Implications

et al. 2018

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“…The observation target in our method is the azimuthal amplitude variation of the conversions and not the splitting signal. Even for the synthetic cases here with a large anisotropic layer thickness of 15 km with a relatively strong coherent anisotropy of 13%, the splitting of the bottomside conversion is 0.5 s. In realistic cases with thinner layers of crustal anisotropy (e.g., shear zones), the splitting will be significantly less, and observational evidence places most around a maximum of ~0.3 s, although crustal splitting values up to ~1 s have been proposed for the thick crust of Tibet [ Sun et al ., ; Niu et al ., ].…”

Section: Discussionmentioning

confidence: 99%

Characteristics of deep crustal seismic anisotropy from a compilation of rock elasticity tensors and their expression in receiver functions

et al. 2017

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Rocks in the continental crust are long lived and have the potential to record a wide span of tectonic history in rock fabric. Mapping rock fabric in situ at depth requires the application of seismic methods. Below depths of microcrack closure seismic anisotropy presumably reflects the shape and crystallographic preferred orientations influenced by deformation processes. Interpretation of seismic observables relevant for anisotropy requires assumptions on the symmetry and orientation of the bulk elastic tensor. We compare commonly made assumptions against a compilation of 95 bulk elastic tensors from laboratory measurements, including electron backscatter diffraction and ultrasound, on crustal rocks. The majority of samples developed fabric at pressures corresponding to middle to lower crustal condition. Tensor symmetry is a function of mineral modal composition, with mica‐rich samples trending toward hexagonal symmetry, amphibole‐rich samples trending toward an increased orthorhombic symmetry component, and quartz‐feldspar‐rich samples showing a larger component of lower symmetries. Seventy‐seven percent of samples have a best fit hexagonal tensor with slow‐axis symmetry, as opposed to mantle deformation fabric that usually has fast‐axis symmetry. The best fit hexagonal approximation for crustal tensors is not elliptical but deviates systematically from elliptical symmetry with increasing anisotropy, an observation that affects the magnitude and orientation of anisotropy inferred from receiver function and surface wave observations. We present empirical linear relationships between anisotropy and ellipticity for crustal rocks. The maximum out‐of‐plane conversion amplitudes in receiver functions scale linearly with degree of anisotropy for nonelliptical symmetry. The elliptical assumption results in a bias of up to 1.4 times true anisotropy.

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S-Wave Velocity Images of the Crust in the Southeast Margin of Tibet Revealed by Receiver Functions

Peng

Badal

et al. 2019

Pure Appl. Geophys.

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Crustal structure and deformation under the Longmenshan and its surroundings revealed by receiver function data

Cited by 42 publications

References 72 publications

Crustal Azimuthal Anisotropy Beneath the Southeastern Tibetan Plateau and its Geodynamic Implications

Crustal Azimuthal Anisotropy Beneath the Southeastern Tibetan Plateau and its Geodynamic Implications

Characteristics of deep crustal seismic anisotropy from a compilation of rock elasticity tensors and their expression in receiver functions

S-Wave Velocity Images of the Crust in the Southeast Margin of Tibet Revealed by Receiver Functions

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