Upper mantle anisotropy and crust-mantle deformation pattern beneath the Chinese mainland

Wang, Chun-Yong; Chang, Ling; Ding, Zhongli; Liu, QiongLin; Liao, Wulin; Flesch, L. M.

doi:10.1007/s11430-013-4675-5

Cited by 18 publications

(10 citation statements)

References 71 publications

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“…The average delay time beneath the northeastern Ordos block and eastern IMSZ is nearly 1.2 s, slightly larger than that measured beneath eastern and central China (0.92 s, Wang, Chang, et al, 2014). Another notable feature is the obvious change in fast-wave polarization direction from NW-SE beneath the Yinshan Belt and Inner Mongolia Suture Zone to nearly W-E and NEE-SWW beneath the TNCO.…”

Section: Resultsmentioning

confidence: 59%

Shear Wave Splitting Evidence for Keel‐Deflected Mantle Flow at the Northern Margin of the Ordos Block and Its Implications for the Ongoing Modification of Craton Lithosphere

Guo

Chen

et al. 2020

JGR Solid Earth

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We use 123 temporary seismic stations to determine shear wave splitting patterns beneath the northern Ordos block and its surrounding areas. The mapped pattern of anisotropy shows a dramatic arc-shaped anisotropy contrast beneath the northeastern Ordos block that closely follows the lateral fast/slow-velocity interface seen in a recent surface tomographic model at~140 km depth. Both seismic anisotropy and velocity appear to demarcate the current boundary of cratonic lithosphere in the upper mantle at this depth, located >150 km south of the geological surface boundary of cratonic crust. We suggest that the craton's keel in the northeastern corner of Ordos block has already been eroded and replaced by warmer asthenospheric mantle, while the cratonic crust above this "missing" keel has yet to be destroyed by deformation and/or crustal metamorphism, thus creating the keel divot at the northeastern corner of the Ordos block. The fast polarization direction of anisotropy tends to wrap around the northeastern margin of the Ordos block, changing from predominantly NW-SE beneath the western part of the margin to nearly E-W beneath the east. We suggest this pattern reflects that plate motion-related asthenosphere flow is being deflected by the cratonic keel of the Ordos block. Such keel-deflected asthenospheric flow could enhance the erosion of the craton's keel, leading to the observed lithospheric reworking beneath this region.

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Section: Resultsmentioning

confidence: 59%

Shear Wave Splitting Evidence for Keel‐Deflected Mantle Flow at the Northern Margin of the Ordos Block and Its Implications for the Ongoing Modification of Craton Lithosphere

Guo

Chen

et al. 2020

JGR Solid Earth

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“…The FVDs of P wave azimuthal anisotropy in east China (including northeast China, north China, and southeast China) are very complex (Figure ), showing considerable variations in different regions (Figure ). The P wave result is in strong contrast with the pattern of SKS splitting measurements which show robust FVDs of NW‐SE to NWW‐SEE from northeast China to south China [e.g., Chang et al , ; Huang et al , ; Wang et al , ]. Thus, the SKS splitting observed in east China is not mainly caused by the anisotropy in the lithosphere.…”

Section: Discussionmentioning

confidence: 83%

“…Shear wave splitting measurements with long‐period core phases such as SKS generally reflect the anisotropy in the crust and upper mantle under the seismograph stations. So far, many researchers have used SKS splitting measurements to study seismic anisotropy beneath China and its adjacent regions [e.g., Huang et al , ; Wang et al , ] (Figure ). In particular, seismic anisotropy in and around the Tibetan Plateau has attracted special attention [e.g., Wang et al , ; Chen et al , ; Wei et al , ].…”

Section: Introductionmentioning

confidence: 99%

Three‐dimensional P wave azimuthal anisotropy in the lithosphere beneath China

et al. 2014

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Seismic anisotropy in the upper mantle beneath East Asia has been studied extensively using shear wave (SKS) splitting measurements, which have provided important information on mantle dynamics in this region. However, SKS measurements have poor vertical resolution, and so their interpretations are usually not unique. In this work we use a large number of traveltime data from 34,036 local earthquakes recorded by 1563 seismic stations to determine the first model of 3-D P wave azimuthal anisotropy in the lithosphere beneath China. Our results show that the fast velocity directions (FVDs) are generally correlated with the surface geologic features, such as the strikes of the orogens, active faults, and tectonic boundaries. The FVDs in the upper crust are normal to the maximal horizontal stress (σ H ) in regions with extensive compression such as the Tibetan Plateau, whereas they are subparallel to σ H in strike-slip shear zones such as the western and eastern Himalayan syntax. The comparison of the FVDs of P wave anisotropy with SKS splitting measurements indicates that beneath the Tibetan Plateau the seismic anisotropy in the lithosphere contributes significantly to the SKS splitting observations. In contrast, in east China the P wave FVDs in the lithosphere are different from the SKS splitting measurements, suggesting that the SKS splitting is mainly caused by the anisotropy in the deeper mantle such as the asthenosphere and the mantle transition zone under east China. These novel results provide important new information on the lithospheric deformation and mantle dynamics in East Asia.

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“…These weak material regions are dominated by strongly positive radial anisotropy (V SH > V SV ), indicating that they are subjected by intense horizontal strain, which makes them possible to flow on a geological time scale. According to our model, the shear wave traveltime in a 120 km thick lithosphere is about 26.7 s (the average S-wave velocity is ~ 4.5 km/s) associated with the 4% anisotropy, then the traveltime delay between the fast and low S-wave is ~ 1.1 s. The average time delay of SKS wave splitting in the central-eastern part of North China is ~ 1.0 s with the NW–SE fast S-wave direction (Liu et al 86 ; Wang et al 87 ; Zhu and Ma 88 ), which support our claim of horizontal mantle flow. Moreover, GPS measurements show that the current crust of the North China region is moving in the direction of NW–SE (Wang et al 89 ), which is also the direction of subduction and retreat of the Western Pacific slab.…”

Section: Resultsmentioning

confidence: 99%

Adjoint traveltime tomography unravels a scenario of horizontal mantle flow beneath the North China craton

Dong

Yang

Niu

et al. 2021

Sci Rep

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The North China craton (NCC) was dominated by tectonic extension from late Cretaceous to Cenozoic, yet seismic studies on the relationship between crust extension and lithospheric mantle deformation are scarce. Here we present a three dimensional radially anisotropic model of NCC derived from adjoint traveltime tomography to address this issue. We find a prominent low S-wave velocity anomaly at lithospheric mantle depths beneath the Taihang Mountains, which extends eastward with a gradually decreasing amplitude. The horizontally elongated low-velocity anomaly is also featured by a distinctive positive radial anisotropy (VSH > VSV). Combining geodetic and other seismic measurements, we speculate the presence of a horizontal mantle flow beneath central and eastern NCC, which led to the extension of the overlying crust. We suggest that the rollback of Western Pacific slab likely played a pivotal role in generating the horizontal mantle flow at lithospheric depth beneath the central and eastern NCC.

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Upper mantle anisotropy and crust-mantle deformation pattern beneath the Chinese mainland

Cited by 18 publications

References 71 publications

Shear Wave Splitting Evidence for Keel‐Deflected Mantle Flow at the Northern Margin of the Ordos Block and Its Implications for the Ongoing Modification of Craton Lithosphere

Shear Wave Splitting Evidence for Keel‐Deflected Mantle Flow at the Northern Margin of the Ordos Block and Its Implications for the Ongoing Modification of Craton Lithosphere

Three‐dimensional P wave azimuthal anisotropy in the lithosphere beneath China

Adjoint traveltime tomography unravels a scenario of horizontal mantle flow beneath the North China craton

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