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已有 3022 次阅读 2013-8-18 22:49 |系统分类:论文交流| 四川盆地, 地震灾害, 龙门山褶皱带, 断层相关褶皱

Structural geometry and deformation mechanism of the Longquan anticline inthe Longmen Shan fold-and-thrust belt, eastern Tibet

Zhigang Li, Dong Jia, Wei Chen

The 2008 Mw 7.9 Wenchuan earthquake is a consequence of ongoing India-Tibet collision and reflects the growth of the Longmen Shan fold-and-thrust belt. In this paper, we present new constraints on the deformation mechanism of the Longmen Shan fold-and-thrust belt, by comparing the physical models to the example of the Longmen Shan fold-and-thrust belt. The result indicates that the deformation mechanism of the belt is mainly dominated by the pre-Sinian layer, whereas locally is controlled by the Lower Triassic layer, such as the Longquan anticline. In addition, we discuss the deformation style of the Longquan anticline various along strike, based on the seismic reflection data, interpretations of structural cross-sections and field observations, as well as physical modeling. The sandbox modeling suggests thatthe deformation of the central segmentof Longquan anticline is likely controlled by higher displacement rate, higher erosion and lower sedimentation, which is incontrast with the southern and northern segment. Moreover, the structural geometry of the central segment of Longquan anticline is more complex than the end-member models of fault-related folds,which is mainly controlled by pure-shear wedge fault-bend fold and bounded by west-verging thrust fault.

Combining the studies of the structural geometry, deformation mechanism, and previous studies, we infer that the Longquan anticline is active and potentially seismogenic. Therefore, a quantitative re-evaluation of seismic hazard in Longquan anticline and adjacent area directly beneath the densely populated Sichuan basin is urgently needed.






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