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Science China Earth Sciences

, Volume 63, Issue 1, pp 121–131 | Cite as

Dynamic mechanisms controlling the topography of Longmenshan area

  • Yuan Xie
  • Yongdong Li
  • Xiong XiongEmail author
Research Paper
  • 37 Downloads

Abstract

The Longmenshan fault, which defines the eastern edge of the Tibetan Plateau, is one of the steepest margins of the plateau with a sharp elevation drop of about 4 km over a distance less than 100 km across the Longmenshan fault. The mechanism which is responsible for controlling and maintaining the elevation difference is highly debated. Using multiple observations including seismic velocity model, Moho depth, effective elastic thickness of the lithosphere, we conducted a quantitative study for elucidating the contributions from crust and lithospheric mantle by an integrated analysis of lithospheric isostasy and flexure. It is shown that the topography of the Longmenshan fault is supported by both lithospheric isostasy and flexure statically, and lower crustal channel flow and mantle convection dynamically. Different mechanisms have different weights for contribution to the topography of the Songpan-Ganzi block and the Sichuan Basin. The static and dynamic support contribute roughly the same to the topographic difference of ~4 km between the two sides of the Longmenshan fault. The static topographic difference of ~2 km is mainly resulted from the lithospheric isostasy, while the dynamic one of ~2 km is contributed by the uprising of the accumulated material in the lower crust beneath the Songpan-Ganzi block and the downward drag force caused by the upper mantle convection under the Sichuan Basin. It is thus suggested that the lower crustal flow and upper mantle convection are dynamic forces which should be taken into account in the studies on the dynamics in the Longmenshan and surrounding regions.

Keywords

Topography Longmenshan fault zone Lithospheric isostasy Lithospheric flexure Dynamic topography 

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Notes

Acknowledgements

We thank Dr. Weisen Shen of University of Colorado at Boulder for the seismic tomography data set, and anonymous reviewers for their insightful review and thoughtful comments. We thank Ms. Yashan Feng for editing the English version of the manuscript. Most figures were prepared with the Generic Mapping Tools (Wessel and Smith, 1998). This work was supported by the National Key R & D Program of China (Grant No. 2017YFC1500305) and the National Natural Science Foundation of China (Grant Nos. 41731072 & 41574095).

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Copyright information

© Science China Press and Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Hubei Subsurface Multi-Scale Imaging Key Laboratory, Institute of Geophysics and GeomaticsChina University of GeosciencesWuhanChina

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