Crustal structure beneath SE Tibet from joint analysis of receiver functions and Rayleigh wave dispersion

Sun, Xiaoxiao; Bao, Xuewei; Xu, Mingjie; Eaton, David W.; Song, Xiaodong; Wang, Liangshu; Ding, Zhongli; Mi, Ning; Yu, Dan; Hua, Li

doi:10.1002/2014gl059269

Cited by 72 publications

(56 citation statements)

References 43 publications

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“…7) throughout the mid-crust in most of Tibet has also been observed in a number of previous studies (e.g. Cotte et al 1999;Rapine et al 2003;Caldwell et al 2009;Guo et al 2009;Li et al 2009;Yang et al 2012;Agius & Lebedev 2014;Jiang et al 2014;Li et al 2014;Sun et al 2014;Bao et al 2015;Deng et al 2015;Gilligan et al 2015). Our results have high resolution across the entire Tibetan Plateau and the Pamirs, whereas many previous studies have mainly focused on more restricted geographical regions.…”

Section: P O S S I B L E C Au S E O F T H E L O W V E L O C I T Y L Asupporting

confidence: 85%

Lateral variations in the crustal structure of the Indo–Eurasian collision zone

Gilligan

2018

Geophysical Journal International

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S U M M A R YThe processes involved in continental collisions remain contested, yet knowledge of these processes is crucial to improving our understanding of how some of the most dramatic features on the Earth have formed. As the largest and highest orogenic plateau on the Earth today, Tibet is an excellent natural laboratory for investigating collisional processes. To understand the development of the Tibetan Plateau, we need to understand the crustal structure beneath both Tibet and the Indian Plate. Building on previous work, we measure new group velocity dispersion curves using data from regional earthquakes (4424 paths) and ambient noise data (5696 paths), and use these to obtain new fundamental mode Rayleigh wave group velocity maps for periods from 5 to 70 s for a region including Tibet, Pakistan and India. The dense path coverage at the shortest periods, due to the inclusion of ambient noise measurements, allows features of up to 100 km scale to be resolved in some areas of the collision zone, providing one of the highest resolution models of the crust and uppermost mantle across this region. We invert the Rayleigh wave group velocity maps for shear wave velocity structure to 120 km depth and construct a 3-D velocity model for the crust and uppermost mantle of the Indo-Eurasian collision zone. We use this 3-D model to map the lateral variations in the crust and in the nature of the crust-mantle transition (Moho) across the Indo-Eurasian collision zone. The Moho occurs at lower shear velocities below northeastern Tibet than it does beneath western and southern Tibet and below India. The east-west difference across Tibet is particularly apparent in the elevated velocities observed west of 84• E at depths exceeding 90 km. This suggests that Indian lithosphere underlies the whole of the Plateau in the west, but possibly not in the east. At depths of 20-40 km our crustal model shows the existence of a pervasive mid-crustal low velocity layer (∼10% decrease in velocity, V s < 3.4 km s −1 ) throughout all of Tibet, as well as beneath the Pamirs, but not below India. The thickness of this layer, the lowest velocity in the layer and the degree of velocity reduction vary across the region. Combining our Rayleigh wave observations with previously published Love wave dispersion measurements, we find that the low velocity layer has a radial anisotropic signature with V sh > V sv . The characteristics of the low velocity layer are supportive of deformation occurring through ductile flow in the mid-crust.

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Section: P O S S I B L E C Au S E O F T H E L O W V E L O C I T Y L Asupporting

confidence: 85%

Lateral variations in the crustal structure of the Indo–Eurasian collision zone

Gilligan

2018

Geophysical Journal International

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“…The mechanically weak midlower crust has also been supported by several lines of evidence from geophysical observations, such as intra-crustal LVZs (Bao et al, 2013;Ceylan et al, 2012;Fu et al, 2010;Li et al, 2008;Xu et al, 2013a;Xu and Song, 2010;Yang et al, 2012;Yao et al, 2008), low electrical resistivity in the mid-lower crust (Bai et al, 2010;Unsworth et al, 2005;Wei et al, 2001), high V p /V s ratios (Sun et al, 2014;Xu et al, 2007), high heat flow (Hu et al, 2000), and strong attenuation (Bao et al, 2011a;Zhao et al, 2013), indicating the existence of partial melt and viscosity reduction in the mid-lower crust and thus the possibility of crustal flow. In addition, strong positive radial anisotropy with faster horizontally polarized shear wave further suggests sub-horizontal alignment of mica and/or amphiboles in the crust due to ductile flow beneath SE Tibet (Huang et al, 2010;Shapiro et al, 2004;Xie et al, 2013).…”

Section: Implications For the Deformation Of Se Tibetmentioning

confidence: 70%

“…Recent studies suggest that there may exist two channels of crustal flow in SE Tibet (Bai et al, 2010;Sun et al, 2014;Zhao et al, 2013). On the basis of magnetotelluric images, Bai et al (2010) observed two channels of high conductivity at depths of 20-40 km in east Tibet, which they interpreted as distinct channels of crustal flow.…”

Section: Implications For the Deformation Of Se Tibetmentioning

confidence: 99%

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Two crustal low-velocity channels beneath SE Tibet revealed by joint inversion of Rayleigh wave dispersion and receiver functions

Bao

Sun

et al. 2015

Earth and Planetary Science Letters

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268

233

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“…The P wave tomography conducted by Lei and Zhao found that broad high-V anomalies are visible from the Burma arc northward in the mantle transition zone (MTZ) beneath eastern Tibet, which is also the case in several other studies [45][46][47], and it has been inferred that they may represent the eastward subduction of the Indian slab along the Burmese arc. That our high-D anomalies are at a depth of 400-500 km (the depth of the MTZ) provides additional evidence for eastward subduction.…”

Section: Discussionmentioning

confidence: 67%

Crustal and Upper Mantle Density Structure Beneath the Qinghai-Tibet Plateau and Surrounding Areas Derived from EGM2008 Geoid Anomalies

Fang

2016

IJGI

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Abstract:As the most active plateau on the Earth, the Qinghai-Tibet Plateau (TP) has a complex crust-mantle structure. Knowledge of the distribution of such a structure provides information for understanding the underlying geodynamic processes. We obtain a three-dimensional model of the density of the crust and the upper mantle beneath the TP and surrounding areas from height anomalies using the Earth Gravitational Model 2008 (EGM2008). We refine the estimated density in the model iteratively using an initial density contrast model. We confirm that the EGM2008 products can be used to constrain the crust-mantle density structures. Our major findings are: (1) At a depth of 300-400 km, high-D(ensity) anomalies terminate around the Jinsha River Suture (JRS) in the central TP, which suggests that the Indian Plate has reached across the Bangong Nujiang Suture (BNS) and almost reaches the JRS. (2) On the eastern TP, low-D(ensity) anomalies at a depth of 0-300 km and with high-D anomalies at 400-670 km further verified the current eastward subduction of the Indian Plate. The ongoing subduction process provides force that results in frequent earthquakes and volcanoes. (3) At a depth of 600 km, low-D anomalies inside the TP illustrate the presence of hot weak material beneath it, which contribute to the inward thrusting of external material.

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Crustal structure beneath SE Tibet from joint analysis of receiver functions and Rayleigh wave dispersion

Cited by 72 publications

References 43 publications

Lateral variations in the crustal structure of the Indo–Eurasian collision zone

Lateral variations in the crustal structure of the Indo–Eurasian collision zone

Two crustal low-velocity channels beneath SE Tibet revealed by joint inversion of Rayleigh wave dispersion and receiver functions

Crustal and Upper Mantle Density Structure Beneath the Qinghai-Tibet Plateau and Surrounding Areas Derived from EGM2008 Geoid Anomalies

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