Mapping crustal structure beneath southern Tibet: Seismic evidence for continental crustal underthrusting

Xu, Qiang; Zhao, Junmeng; Yuan, Xiaohui; Liu, Hongbing; Pei, Shunping

doi:10.1016/j.gr.2014.01.006

Cited by 70 publications

(66 citation statements)

References 43 publications

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“…As the most effective and practical geophysical methods, seismic imaging (Gao et al 2013;Karplus et al 2011;Kind et al 2002;Nabelek et al 2009;Nabelek and Nabelek 2014;Xu et al 2015a, b;Zhang et al 2011Zhang et al , 2013Zhao et al 2011Zhao et al , 2014aZhao and Nelson 1993) and magnetotelluric (MT) data modeling (Chen et al 1996;Le Pape et al 2012;Unsworth et al 2004Unsworth et al , 2005Wei et al 2001) have been widely applied to study the deep evolution and tectonic processes of the plateau over the past decades. Results of previous seismological studies have revealed some details for the extension Liang et al 2016;Tian et al 2015;Xu et al 2015a;Zhang et al 2015Zhang et al , 2016Zhang et al , 2011Zhao et al 2014b) and we believe that MT data can provide some indirect information to obtain a more comprehensive model. In this paper, we reprocessed previous MT data that were deployed in southern Tibet (Fig.…”

Section: Introductionmentioning

confidence: 75%

“…Seismic studies show the variation of the Moho depth in both N-S and east-west (E-W) directions and the Moho step under the main sutures. Along the N-S direction, the Moho depth shows a trend of gradually thinning from the southern part to the northern part beneath Tibet and the maximum thickness (~ 75-80 km) is located in the Lhasa terrane along the Yarlung-Zangbo sutures (YZS) (Kind et al 2002;Xu et al 2015a;Zhang et al 2011). In the E-W direction, the western part of the plateau has a thicker crust than the eastern part and the possible Moho step is imaged under the main sutures (Gao et al 2009).…”

Section: Introductionmentioning

confidence: 99%

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Varying Indian crustal front in the southern Tibetan Plateau as revealed by magnetotelluric data

Xie

Jin

Wei

et al. 2017

Earth Planets Space

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In the southern Tibetan plateau, which is considered to be the ongoing India-Eurasia continental collision zone, tracing of the Indian crustal front beneath Tibet is still controversial. We conducted deep subsurface electrical modeling in southern Tibet and discuss the geometry of the front of the Indian crust. Three areas along the Yarlung-Zangbo river zone for which previous magnetotelluric (MT) data are available were inverted independently using a three-dimensional MT inversion algorithm ModEM. Electrical horizontal slices at different depths and north-south oriented cross sections at different longitudes were obtained to provide a geoelectrical perspective for deep processes beneath the Tethyan Himalaya and Lhasa terrane. Horizontal slices at depths greater than − 15 km show that the upper crust is covered with resistive layers. Below a depth of − 20 km, discontinuous conductive distributions are primarily concentrated north of the Yarlung-Zangbo sutures (YZS) and could be imaged from mid-to lower crust. The results show that the maximum depth to which the resistive layers extend is over − 20 km, while the mid-to lower crustal conductive zones extend to depths greater than − 50 km. The results indicate that the conductive region in the mid-to lower crust can be imaged primarily from the YZS to south of the Bangong-Nujiang sutures in western Tibet and to ~ 31°N in eastern Tibet. The northern front of the conductive zones appears as an irregular barrier to the Indian crust from west to east. We suggest that a relatively less conductive subsurface in the northern portion of the barrier indicates a relatively cold and strong crust and that the front of the Indian crust might be halted in the south of the barrier. We suggest that the Indian crustal front varies from west to east and has at least reached: ~ 33.5°N at ~ 80°E, ~ 31°N at ~ 85°E, and ~ 30.5°N at ~ 87°E and ~ 92°E.

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Section: Introductionmentioning

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Varying Indian crustal front in the southern Tibetan Plateau as revealed by magnetotelluric data

Xie

Jin

Wei

et al. 2017

Earth Planets Space

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“…The crustal architecture of the eastern Himalaya is revealed through images along profile D‐D

^{'}

covering the Bengal Basin to northern Tibet (up to Bangong‐Nujiang Suture Zone, BNSZ; Figure ). Earlier studies produced high‐quality migrated images of RFs from north of the MCT (Shi et al, ; Xu et al, ). Migrated images produced from south of the MCT in the eastern Himalaya are restricted to data from a few seismic stations located over Northeast India and Bengal Basin (Ramesh et al, , Singh et al, ).…”

Section: Image Of the Crustmentioning

confidence: 99%

Crustal Structure Beneath India and Tibet: New Constraints From Inversion of Receiver Functions

et al. 2017

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The Indian subcontinent comprises geological terranes of varied age and structural character. In this study, we provide new constraints to existing crustal models by inverting the P‐to‐s receiver functions (RFs) at 317 broadband seismic stations. Inversion results fill crucial gaps in existing velocity models (CRUST1.0 and SEAPS) by capturing regions which are less represented. The final model produced is much more heterogeneous and is able to capture the structural variations between closely spaced seismic stations. In comparison to the global models, major differences are seen for seismic stations located over various rift zones (e.g., Godavari, Narmada, and Cambay) and those close to the coastal regions where transition from oceanic to continental crust is expected to create drastic changes in the crustal configuration. Seismic images are produced along various profiles using 49,682 individual RFs recorded at 442 seismic stations. Lateral variations captured using migrated images across the Himalayan collisional front revealed the hitherto elusive southern extent of the Moho and intracrustal features south of the Main Central Thrust (MCT). Poisson's ratio and crustal thickness estimates obtained using H‐k stacking technique and inversion of RFs are grossly similar lending credence to the robustness of inversions. An updated crustal thickness map produced using 1,525 individual data points from controlled source seismics and RFs reveals a (a) thickened crust (>55 km) at the boundary of Dharwar Craton and Southern Granulite Terrain, (b) clear difference in crustal thickness estimates between Eastern Dharwar Craton and Western Dharwar Craton, (c) thinner crust beneath Cambay Basin between southwest Deccan Volcanic Province and Delhi‐Aravalli Fold Belt, (d) thinner crust (<35 km) beneath Bengal Basin, (e) thicker crust (>40 km) beneath paleorift zones like Narmada Son Lineament and Godavari Graben, and (f) very thick crust beneath central Tibet (>65 km) with maximum lateral variations along the Himalayan collision front.

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“…Midcrustal low‐velocity zones (LVZs) at depths of 15–40 km have been widely observed in the eastern Tibetan Plateau using diverse geophysical methods, including active source seismic experiments (Brown et al, ; Nelson et al, ), ambient noise tomography (Yang et al, ), and receiver functions (Xu et al, ). These midcrustal LVZs coincide with high‐conductivity (low resistivity) zones that have been identified by magnetotelluric (MT) studies (Wei et al, ).…”

Section: Introductionmentioning

confidence: 99%

Detailed Configuration of the Underthrusting Indian Lithosphere Beneath Western Tibet Revealed by Receiver Function Images

Zhao

Yuan

et al. 2017

JGR Solid Earth

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We analyze the teleseismic waveform data recorded by 42 temporary stations from the Y2 and ANTILOPE‐1 arrays using the P and S receiver function techniques to investigate the lithospheric structure beneath western Tibet. The Moho is reliably identified as a prominent feature at depths of 55–82 km in the stacked traces and in depth migrated images. It has a concave shape and reaches the deepest location at about 80 km north of the Indus‐Yarlung suture (IYS). An intracrustal discontinuity is observed at ~55 km depth below the southern Lhasa terrane, which could represent the upper border of the eclogitized underthrusting Indian lower crust. Underthrusting of the Indian crust has been widely observed beneath the Lhasa terrane and correlates well with the Bouguer gravity low, suggesting that the gravity anomalies in the Lhasa terrane are induced by topography of the Moho. At ~20 km depth, a midcrustal low‐velocity zone (LVZ) is observed beneath the Tethyan Himalaya and southern Lhasa terrane, suggesting a layer of partial melts that decouples the thrust/fold deformation of the upper crust from the shortening and underthrusting in the lower crust. The Sp conversions at the lithosphere‐asthenosphere boundary (LAB) can be recognized at depths of 130–200 km, showing that the Indian lithospheric mantle is underthrusting with a ramp‐flat shape beneath southern Tibet and probably is detached from the lower crust immediately under the IYS. Our observations reconstruct the configuration of the underthrusting Indian lithosphere and indicate significant along strike variations.

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Mapping crustal structure beneath southern Tibet: Seismic evidence for continental crustal underthrusting

Cited by 70 publications

References 43 publications

Varying Indian crustal front in the southern Tibetan Plateau as revealed by magnetotelluric data

Varying Indian crustal front in the southern Tibetan Plateau as revealed by magnetotelluric data

Crustal Structure Beneath India and Tibet: New Constraints From Inversion of Receiver Functions

Detailed Configuration of the Underthrusting Indian Lithosphere Beneath Western Tibet Revealed by Receiver Function Images

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