High-resolution lithospheric structure beneath Mainland China from ambient noise and earthquake surface-wave tomography

Bao, Xuewei; Song, Xiaodong; Li, Jiangtao

doi:10.1016/j.epsl.2015.02.024

Cited by 214 publications

(201 citation statements)

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“…A continuous low velocity anomaly in the QOB, an area between the Haiyuan fault and the east Kunlun fault, is generally imaged at periods from 20 to 100 s (Figures a–e). The observation of this low velocity anomaly is consistent with previous Rayleigh wave tomography models (Bao, Song, & Li, ; Li et al, ), while it is partially different from a relatively high velocity in the north QOB obtained from previous Rayleigh and Love wave tomography study (Li et al, , ), which has limited station coverage and crossing ray paths there. The Songpan‐Ganzi terrane (SGT) is characterized by low velocity anomaly at periods less than 50 s (Figures a and b) and relatively high velocity compared with the QOB at periods of 59–100 s. Another interesting feature is the sharp velocity contrast between high phase velocities in the Ordos block (OB) and low phase velocities in the Alxa block (AB) at intermediate‐long periods (>45 s) (Figures c–e).…”

Section: Resultssupporting

confidence: 89%

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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Section: Resultssupporting

confidence: 89%

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

Xiao

2019

JGR Solid Earth

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“…The most striking feature of our tomographic results is that obvious low‐ V anomalies exist widely in the lower crust beneath the Qilian Orogenic Belt and Western Qinling (Figures , , and ), which have been also revealed by the previous seismic studies [e.g., Tian et al , ; Wang et al , ; J. Wang et al , ; Zhang et al , ; Bao et al , ]. However, the details of our tomographic images are different from those obtained by the previous studies, perhaps due to the higher resolution of our tomographic model.…”

Section: Interpretation and Discussionmentioning

confidence: 97%

Seismic tomography and anisotropy of the Helan‐Liupan tectonic belt: Insight into lower crustal flow and seismotectonics

et al. 2016

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We determined detailed 3‐D P and S wave velocities (Vp and Vs) and Poisson's ratio (σ) images as well as P wave azimuthal anisotropy in the crust and uppermost mantle beneath the Helan‐Liupan tectonic belt (HLTB) and adjacent regions. The data set used in this study consists of 38,880 P wave and 35,117 S wave arrival times from 5028 local earthquakes recorded by 66 seismic stations in the study area during 1980 to 2014. Obvious low‐Vp and low‐σ anomalies are revealed in the lower crust beneath the Qilian Orogenic Belt and Western Qinling, which we interpret as a weakened zone mainly caused by water and capable of ductile flow on a geological timescale. Our P wave anisotropy results suggest that the flow direction in the lower crust is nearly parallel to the direction of the geodetic crustal motion and that of the upper mantle flow beneath the study region. Most of the 26 large historical earthquakes (1125–1954) in the study region occurred in the boundary zones where Vp, Vs, and σ change drastically over a short distance. Beneath the source areas of the large historical earthquakes, fluid‐related low‐velocity zones exist widely in the lower crust. The fluids result from dehydration of hydrous minerals in the deeper crust and uppermost mantle beneath the northeastern Tibetan Plateau. When the fluids migrate upward to the active faults, the fault zone friction is reduced and so large crustal earthquakes can be triggered. Our present results shed new light on the seismogenesis and geodynamics of the northeastern Tibetan Plateau and adjacent areas.

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“…The depositional thickness decreases southeastward in the Ordos block (Figure ), suggesting that the extensional effect caused by the mantle convection decreased southeastward [ Zhang et al ., ]. The relatively low velocity in the upper mantle beneath the northern Ordos block (Figures g–h) may represent upwelling of asthenospheric material and may indicate that the northern Ordos block experienced lithospheric modification during the Cenozoic [e.g., Bao et al ., ; Wei et al ., ]. Thus, the modification of the lithosphere beneath the Ordos block may also be associated with the mantle flow.…”

Section: Discussionmentioning

confidence: 99%

Three‐dimensional lithospheric S wave velocity model of the NE Tibetan Plateau and western North China Craton

Xingchen

Ding

et al. 2017

JGR Solid Earth

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We present a new 3‐D lithospheric Vs model for the NE Tibetan Plateau (NETP) and the western North China Craton (NCC). First, high‐frequency receiver functions (RFs) were inverted using the neighborhood algorithm to estimate the sedimentary structure beneath each station. Then a 3D Vs model with unprecedented resolution was constructed by jointly inverting RFs and Rayleigh wave dispersions. A low‐velocity sedimentary layer with thicknesses varying from 2 to 10 km is present in the Yinchuan‐Hetao graben, Ordos block, and western Alxa block. Velocities from the middle‐lower crust to the uppermost mantle are generally high in the Ordos block and low in the Alxa block, indicating that the Alxa block is not part of the NCC. The thickened crust in southwestern Ordos block and western Alxa block suggests that they have been modified. Two crustal low‐velocity zones (LVZs) were detected beneath the Kunlun Fault (KF) zone and western Qilian Terrane (QLT). The origin of the LVZ beneath the KF zone may be the combined effect of shear heating, localized asthenosphere upwelling, and crustal radioactivity. The LVZ in the western QLT, representing an early stage of the LVZ that has developed in the KF zone, acts as a decollement to decouple the deformation between the upper and lower crust and plays a key role in seismogenesis. We propose that the crustal deformation beneath the NETP is accommodated by a combination of shear motion, thickening of the upper‐middle crust, and removal of lower crust.

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High-resolution lithospheric structure beneath Mainland China from ambient noise and earthquake surface-wave tomography

Cited by 214 publications

References 50 publications

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

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

Seismic tomography and anisotropy of the Helan‐Liupan tectonic belt: Insight into lower crustal flow and seismotectonics

Three‐dimensional lithospheric S wave velocity model of the NE Tibetan Plateau and western North China Craton

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