Mantle transition zone topography and structure beneath the central Tien Shan orogenic belt

Tian, Xiaobo; Zhao, Dapeng; Zhang, Hongshuang; Tian, You; Zhang, Zhongjie

doi:10.1029/2008jb006229

Cited by 56 publications

(37 citation statements)

References 74 publications

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“…Receiver function analyses showed a crustal thickness of ~60 km beneath the most parts of the Tienshan orogenic belt with variations of ~20 km under the adjacent platforms (Bump and Sheehan, 1998;Oreshin et al, 2002;Vinnik et al, 2004;Kumar et al, 2005). Tian et al (2010) suggested that the detached lithosphere may have descended to the bottom of the mantle transition zone and small-scale upwelling may have ascended from the lower mantle beneath the central Tienshan and adjacent regions. Bouguer gravity anomalies showed that large negative values beneath the Tienshan are attributed to the thickening of lithosphere and downwelling of material beneath the range (Burov et al, 1990).…”

Section: Introductionmentioning

confidence: 98%

Pn anisotropic tomography under the entire Tienshan orogenic belt

Zhou¹,

Lei²

2015

Journal of Asian Earth Sciences

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Section: Introductionmentioning

confidence: 98%

Pn anisotropic tomography under the entire Tienshan orogenic belt

Zhou¹,

Lei²

2015

Journal of Asian Earth Sciences

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“…Receiver-function analysis is an effective tool to map the Moho, 410-and 660-km discontinuities, as well as the subducting slab boundary (e.g., Ai et al, 2005;Shiomi et al, 2006;Kawakatsu and Watada, 2007;Tonegawa et al, 2008;Tian et al, 2010). A combination of receiver-function and tomography methods may enable us to estimate simultaneously velocity discontinuities and 3-D velocity variations (e.g., Hirahara, 2006).…”

Section: Advent Of Subduction-zone Tomographymentioning

confidence: 99%

Tomography and Dynamics of Western-Pacific Subduction Zones

Zhao¹

2012

Monogr. Environ. Earth Planets

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We review the significant recent results of multiscale seismic tomography of the Western-Pacific subduction zones and discuss their implications for seismotectonics, magmatism, and subduction dynamics, with an emphasis on the Japan Islands. Many important new findings are obtained due to technical advances in tomography, such as the handling of complex-shaped velocity discontinuities, the use of various later phases, the joint inversion of local and teleseismic data, tomographic imaging outside a seismic network, and P-wave anisotropy tomography. Prominent low-velocity (low-V ) and high-attenuation (low-Q) zones are revealed in the crust and uppermost mantle beneath active arc and back-arc volcanoes and they extend to the deeper portion of the mantle wedge, indicating that the low-V /low-Q zones form the sources of arc magmatism and volcanism, and the arc magmatic system is related to deep processes such as convective circulation in the mantle wedge and dehydration reactions in the subducting slab. Seismic anisotropy seems to exist in all portions of the Northeast Japan subduction zone, including the upper and lower crust, the mantle wedge and the subducting Pacific slab. Multilayer anisotropies with different orientations may have caused the apparently weak shear-wave splitting observed so far, whereas recent results show a greater effect of crustal anisotropy than previously thought. Deep subduction of the Philippine Sea slab and deep dehydration of the Pacific slab are revealed beneath Southwest Japan. Significant structural heterogeneities are imaged in the source areas of large earthquakes in the crust, subducting slab and interplate megathrust zone, which may reflect fluids and/or magma originating from slab dehydration that affected the rupture nucleation of large earthquakes. These results suggest that large earthquakes do not strike anywhere, but in only anomalous areas that may be detected with geophysical methods. The occurrence of deep earthquakes under the Japan Sea and the East Asia margin may be related to a metastable olivine wedge in the subducting Pacific slab. The Pacific slab becomes stagnant in the mantle transition zone under East Asia, and a big mantle wedge (BMW) has formed above the stagnant slab. Convective circulations and fluid and magmatic processes in the BMW may have caused intraplate volcanism (e.g., Changbai and Wudalianchi), reactivation of the North China craton, large earthquakes, and other active tectonics in East Asia. Deep subduction and dehydration of continental plates (such as the Eurasian plate, Indian plate and Burma microplate) are also found, which have caused intraplate magmatism (e.g., Tengchong) and geothermal anomalies above the subducted continental plates. Under Kamchatka, the subducting Pacific slab shortens toward the north and terminates near the Aleutian-Kamchatka junction. The slab loss was induced by friction with the surrounding asthenosphere, as the Pacific plate rotated clockwise 30 Ma ago, and then it was enlarged by the slab-edge pinch-off b...

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“…At the base of the subducted high velocity anomalies, the clearly identified narrow anomalous zone expands gradually from a depth of about 70 km to the middle crust where it finally merges with the low velocity anomalies beneath the Tianshan Mountains. We suggest that part of the lower crust, as featured by low velocity anomalies [40,41] represents a zone of weakness caused by the crust there being heated by heat transfer from the upper mantle. This may help us to understand the mechanism of Tianshan Mountains reactivation associated with the Indian-Eurasian convergence since about 50 Ma.…”

Section: Discussionmentioning

confidence: 97%

S-wave velocity of the crust around Tianshan Mountains inverted from seismic ambient noise tomography

et al. 2010

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We process ambient noise data from seismic stations deployed in central Asia to determine the crustal shear wave velocity structure beneath the Tianshan Mountians and surrounding area. About 748 inter-station Rayleigh wave empirical Green's functions have been recovered to estimate the phase velocity dispersions over periods from 6 to 50 s using the image transformation technique. Results show that for short periods (6-20 s), the distribution of Rayleigh wave phase velocities is generally consistent with surface geology, with high velocities corresponding to mountain ranges and low velocities to sedimentary basins. Along two profiles, which trend from NE-SW and NW-SE, the shear wave velocity shows a pair of high velocity anomalies dipping in opposite directions beneath the Tianshan Mountains. At shallow depths, those high velocity anomalies roughly correlate with areas where the mountain front and the surrounding basin are connected. The profiles also show a narrow zone beneath the Tianshan Mountains, which may represent a route for the upwelling from upper mantle. Those observations suggest that the underthrusting of the Tarim Basin and Kazakh Shield combine with the weakness of the crust, which is heated by the upwelling from upper mantle, may play an important role on the reactivation of the Tianshan Mountains associated with the India-Eurasia collision. ambient noise tomography, Tianshan Mountains, crustal structure, upper mantle upwelling Citation: Guo Z, Gao X, Wang W M, et al. S-wave velocity of the crust around Tianshan Mountains inverted from seismic ambient noise tomography.

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Mantle transition zone topography and structure beneath the central Tien Shan orogenic belt

Cited by 56 publications

References 74 publications

Pn anisotropic tomography under the entire Tienshan orogenic belt

Pn anisotropic tomography under the entire Tienshan orogenic belt

Tomography and Dynamics of Western-Pacific Subduction Zones

S-wave velocity of the crust around Tianshan Mountains inverted from seismic ambient noise tomography

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