Structure of the crust and mantle down to 700 km depth beneath the East Qaidam basin and Qilian Shan from P and S receiver functions

Feng, Min; Kumar, Prakash; Mechie, J.; Zhao, Wenjin; Kind, R.; Su, Hailin; Xue, Guangqi; Shi, Dan; Qian, Hui

doi:10.1093/gji/ggu335

Cited by 39 publications

(31 citation statements)

References 42 publications

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“…The imaged LAB at depths of 105–121 km beneath the QL is supported by the analysis of the stacked S ‐RFs, which demonstrates that the LAB beneath the QL is present at 12–14 s (i.e., depths of 105–125 km; Feng et al, ). The single stacked trace of all the S ‐RFs within the QL also indicates that the negative signal from the LAB is observed at 11 s (100 km; X.…”

Section: Discussionmentioning

confidence: 78%

Seismic Evidence for Lateral Asthenospheric Flow Beneath the Northeastern Tibetan Plateau Derived From S Receiver Functions

Pei

Yuan

et al. 2019

Geochem Geophys Geosyst

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We present detailed lithospheric images of the NE Tibetan Plateau by applying the depth migration technique to S receiver functions derived from 113 broadband stations. Our migrated images indicate that the lithosphere-asthenosphere boundary (LAB) lies at depths of 105-120 km beneath the Qilian terrane and reaches depths of 126-140 km below the Alxa and Ordos blocks. The most prominent variation in the LAB depth is the presence of LAB steps of no less than 20 km in the transition zone between the active NE Tibetan Plateau and the surrounding cratonic Alxa and Ordos blocks, which conflicts with the model of southward subduction of the Alxa and Ordos blocks. Furthermore, the marked LAB steps occur at 130 ± 10 km away from the southern surficial boundary faults between the NE Tibetan Plateau and the surrounding tectonic provinces, corresponding to the North Qilian fault and the Liupanshan fault, respectively. Therefore, we propose that these scenarios of LAB can be attributed to the delamination of fragmented mantle lithosphere in the transition zone between the NE Tibetan Plateau and the surrounding Alxa and Ordos blocks, triggered by lateral asthenospheric flow. In addition, our observations of a thin lithosphere with thickness of 107-115 km beneath the Songpan-Ganzi terrane and the west Qinlin orogen greatly facilitate the process of underlying lateral asthenospheric flow. The isostatic uplift of the plateau caused by the delamination of fragmented mantle lithosphere, together with increased horizontal compressive stress, may have led to the outward growth of the NE Tibetan Plateau.

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Section: Discussionmentioning

confidence: 78%

Seismic Evidence for Lateral Asthenospheric Flow Beneath the Northeastern Tibetan Plateau Derived From S Receiver Functions

Pei

Yuan

et al. 2019

Geochem Geophys Geosyst

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“…In this case the high Tibetan plateau may be starting to thicken southeastward into the southwestern Sichuan basin as weak, thickened lower crust of the Songpan‐Ganzi terrane is injected beneath the stronger crust of the Sichuan basin. Feng et al () show how this may occur in NE Tibet. Further to the north where there is no break in the Moho but rather just a steady increase in Moho depth in going from the Sichuan basin to the high Tibetan plateau, the lithosphere of the Sichuan basin may still be more successfully resisting the advance of the Tibetan plateau.…”

Section: Discussionmentioning

confidence: 99%

“…In doing so, the Computer Programs in Seismology package by Herrmann and Ammon () was partly utilized. Processing steps included band‐pass filtering from 2 to 20 s and rotation from the coordinate system (vertical, NS horizontal, and EW horizontal) in which the data were recorded to a ray‐based ( P , SV , SH or L, Q, T) coordinate system (see e.g., Feng et al, ; Kind et al, , ; Yuan et al, ). The rotation angles were obtained from the back azimuth angle for the horizontal angle and the covariance matrix of the vertical and radial components of the P wave group for the vertical angle (Kind et al, ).…”

Section: Data Processing and Examples And 1‐d Model For The Sichuan Bmentioning

confidence: 99%

Structure of the Crust and Mantle Down to 700 km Depth beneath the Longmenshan From P Receiver Functions

Qian

Mechie

et al. 2018

Tectonics

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Since the Ms 8.0 Wenchuan earthquake occurred in 2008 in the Longmenshan at the eastern margin of Tibet, this region has attracted much attention. In order to investigate the deep structure of the region, an analysis of P receiver functions was carried out, using data from an array of 80 broadband seismic stations operated in 2012 and 2013, and straddling the Longmenshan fault zone around the epicenter of the Wenchuan earthquake. Positive Ps conversions from 5 to 10 km depth indicate the base of the Mesozoic sediments in the Sichuan basin and the base of the Songpan-Ganzi flysch deposits in Tibet. Later positive Ps conversions represent the Moho, which occurs at 40-50 km depth below the Sichuan basin and deepens to the NW to 55-70 km depth under Tibet. An important finding of this study is that whereas in the NE, the Moho deepening from SE to NW is smooth, in the middle and SW of the region the Moho deepening is abrupt with, in some places, a possible overlap. Negative Ps conversions at stations in Tibet represent the top of low shear velocity zones in the middle and lower crusts below Tibet. Beneath the Sichuan basin, a negative phase about 1 s earlier than the Moho Ps conversion is to a large extent, almost certainly due to multiples from discontinuities in the upper crust. Finally, positive Ps conversions can be observed from the 410 and 660-km discontinuities at the top and bottom of the mantle transition zone, respectively.

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“…Present crustal thicknesses reach ~60–70 km in the Qilian Shan, contrasting with ~55 km for the interior of the Qaidam Basin and 45–50 km for the Tarim Basin and Hexi corridor to the northwest and north of the Qilian Shan [ Wang et al ., ; Tian and Zhang , ; Feng et al ., ].…”

Section: Regional Backgroundmentioning

confidence: 99%

Partitioning of oblique convergence coupled to the fault locking behavior of fold‐and‐thrust belts: Evidence from the Qilian Shan, northeastern Tibetan Plateau

et al. 2017

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Oblique plate convergence is common, but it is not clear how the obliquity is achieved by continental fold‐and‐thrust belts. We address this problem in the Qilian Shan, northeastern Tibetan Plateau, using fieldwork observations, geomorphic analysis, and elastic dislocation modeling of published geodetic data. A thrust dips SSW from the northern range front and underlies steeper thrusts in the interior. Cenozoic thrust‐related shortening across the Qilian Shan is ~155–175 km, based on two transects. Elastic dislocation modeling indicates that horizontal strain in the interseismic period is consistent with oblique slip on a single low‐angle detachment thrust below ~26 km depth, dipping SSW at ~17°. We suggest that this detachment is located above North China Block crust, originally underthrust during Paleozoic orogeny. Horizontal shear strain is localized directly above the updip limit of creep on the detachment and is coincident with the left‐lateral Haiyuan Fault. This configuration implies that oblique slip on the detachment below seismogenic depths is partitioned in the shallow crust onto separate strike‐slip and thrust faults. This is consistent with strain partitioning in oceanic subduction zones but has not previously been found by dislocation models of continental interiors. The marginal, strike‐slip, Altyn Tagh Fault influences thrusting within the Qilian Shan for 100–200 km from the fault but does not control the regional structure, where Paleozoic basement faults have been reactivated. The Qilian Shan resembles the main Tibetan Plateau in nascent form: active thrusts are marginal to an interior that is developing plateau characteristics, involving low relief, and low seismicity.

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Structure of the crust and mantle down to 700 km depth beneath the East Qaidam basin and Qilian Shan from P and S receiver functions

Abstract: Qian, H. (2014): Structure of the crust and mantle down to 700 km depth beneath the East Qaidam basin and Qilian Shan from P and S receiver functions.

Cited by 39 publications

References 42 publications

Seismic Evidence for Lateral Asthenospheric Flow Beneath the Northeastern Tibetan Plateau Derived From S Receiver Functions

Seismic Evidence for Lateral Asthenospheric Flow Beneath the Northeastern Tibetan Plateau Derived From S Receiver Functions

Structure of the Crust and Mantle Down to 700 km Depth beneath the Longmenshan From P Receiver Functions

Partitioning of oblique convergence coupled to the fault locking behavior of fold‐and‐thrust belts: Evidence from the Qilian Shan, northeastern Tibetan Plateau

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