Journal: |
Earth and Planetary Science Letters 2009 No.9
clicks:835 |
Title:
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Author:
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J. Liu-Zeng , Z. Zhang, L. Wena, P. Tapponnier, J. Suna, X. Xing, G. Hu, Q. Xu, L. Zeng, L. Ding, C. Ji, K.W. Hudnut, J. van der Woerd |
Adress: |
Key Laboratory of Continental Collision and Plateau uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, 18 Shuang Qing Road, Beijing 100085, China |
Abstract:
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The Ms 8.0, Wenchuan earthquake, which devastated the mountainous western rim of the Sichuan basin in central China, produced a surface rupture over 200 km-long with oblique thrust/dextral slip and maximum scarp heights of ~ 10 m. It thus ranks as one of the world's largest continental mega-thrust events in the last 150 yrs. Field investigation shows clear surface breaks along two of the main branches of the NE-trending Longmen Shan thrust fault system. The principal rupture, on the NW-dipping Beichuan fault, displays nearly equal amounts of thrust and right-lateral slip. Basin-ward of this rupture, another continuous surface break is observed for over 70 km on the parallel, more shallowly NW-dipping Pengguan fault. Slip on this latter fault was pure thrusting, with a maximum scarp height of ~ 3.5 m. This is one of the very few reported instances of crustal-scale co-seismic slip partitioning on parallel thrusts. This out-of-sequence event, with distributed surface breaks on crustal mega-thrusts, highlights regional, ~ EW-directed, present day crustal shortening oblique to the Longmen Shan margin of Tibet. The long rupture and large offsets with strong horizontal shortening that characterize the Wenchuan earthquake herald a re-evaluation of tectonic models anticipating little or no active shortening of the upper crust along this edge of the plateau, and require a re-assessment of seismic hazard along potentially under-rated active faults across the densely populated western Sichuan basin and mountains.
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