Article abstract
Nature Geoscience 2, 718 - 724 (2009)
Published online: 27 September 2009 | doi:10.1038/ngeo636
Subject Categories: Seismology | Structural geology, tectonics and geodynamics
Slip maxima at fault junctions and rupturing of barriers during the 2008 Wenchuan earthquake
Zheng-Kang Shen1,2,3, Jianbao Sun1, Peizhen Zhang1, Yongge Wan4, Min Wang1, Roland Bürgmann5, Yuehua Zeng6, Weijun Gan1, Hua Liao7 & Qingliang Wang8
Abstract
The disastrous 12 May 2008 Wenchuan earthquake in China took the local population as well as scientists by surprise. Although the Longmen Shan fault zone—which includes the fault segments along which this earthquake nucleated—was well known, geologic and geodetic data indicate relatively low (<3 mm yr-1) deformation rates. Here we invert Global Positioning System and Interferometric Synthetic Aperture Radar data to infer fault geometry and slip distribution associated with the earthquake. Our analysis shows that the geometry of the fault changes along its length: in the southwest, the fault plane dips moderately to the northwest but becomes nearly vertical in the northeast. Associated with this is a change in the motion along the fault from predominantly thrusting to strike-slip. Peak slip along the fault occurs at the intersections of fault segments located near the towns of Yingxiu, Beichuan and Nanba, where fatalities and damage were concentrated. We suggest that these locations represent barriers that failed in a single event, enabling the rupture to cascade through several fault segments and cause a major moment magnitude (Mw) 7.9 earthquake. Using coseismic slip distribution and geodetic and geological slip rates, we estimate that the failure of barriers and rupture along multiple segments takes place approximately once in 4,000 years.
- State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, PO Box 9803, Beijing 100029, China
- Department of Geophysics, School of Earth and Space Sciences, Peking University, Beijing 100871, China
- Department of Earth and Space Sciences, University of California, Los Angeles, California 90095-1567, USA
- College of Disaster Prevention Science and Technology, Yanjiao, Sanhe, Hebei 101601, China
- Department of Earth and Planetary Science, University of California, Berkeley, California 94720-4767, USA
- Golden Office, US Geological Survey, Colorado 80401, USA
- Sichuan Seismological Bureau, Chengdu 610041, China
- Second Monitoring Center, China Earthquake Administration, Xi'an 710054, China
Correspondence to: Zheng-Kang Shen1,2,3 e-mail: zshen@ies.ac.cn; e-mail: zshen@ucla.edu
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