Co-seismic ruptures of the 12 May 2008, M-s 8.0 Wenchuan earthquake, Sichuan: East-west crustal shortening on oblique, parallel thrusts along the eastern edge of Tibet | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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  Co-seismic ruptures of the 12 May 2008, M-s 8.0 Wenchuan earthquake, Sichuan: East-west crustal shortening on oblique, parallel thrusts along the eastern edge of Tibet

Type de publication:

Journal Article

Source:

Earth and Planetary Science Letters, Volume 286, Ticket 3-4, p.355-370 (2009)

ISBN:

0012-821X

Numéro d'accès:

ISI:000271358300002

URL:

http://www.sciencedirect.com/science/article/pii/S0012821X09003914

Mots-clés:

UMR 7154 ; Tectonique ; Wenchuan earthquake; Longmen Shan thrust belt; Tibetan plateau; surface rupture; co-seismic slip partitioning; out-of-sequence thrusting earthquake

Résumé:

The M-s 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 similar to 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-clipping Pengguan fault. Slip on this latter fault was pure thrusting, with a maximum scarp height of similar to 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, similar to 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. (C) 2009 Elsevier B.V. All rights reserved.

Notes:

Liu-Zeng, J. Zhang, Z. Wen, L. Tapponnier, P. Sun, J. Xing, X. Hu, G. Xu, Q. Zeng, L. Ding, L. Ji, C. Hudnut, K. W. van der Woerd, J.