Surface deformation related to the 2008 Wenchuan earthquake,and mountain building of the Longmen Shan,eastern Tibetan Plateau |
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| Authors: | Bihong Fu Pilong Shi Huadong Guo Satoshi Okuyama Yoshiki Ninomiya Sarah Wright |
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| Institution: | 1. Department of Earth Sciences and Institute of Energy Sciences, Nanjing University, Nanjing 210093, China;2. Resources and Environment Institute, Southwest Petroleum University, Chengdu 610500, China;3. The Southwest Branch of SINOPEC, Chengdu 610016, China;1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Institute of Sedimentary Geology, Chengdu University of Technology, 610059 Chengdu, Sichuan, China;2. Institute of Geology, Chinese Academy of Geological Science, 100037 Beijing, China;3. Institute of Earthquake Engineering, Seismological Bureau of Sichuan Province, Chengdu 610041, Sichuan, China;1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation/Chengdu University of Technology, Chengdu, China;2. Institute für Geowissenschaften, Universität Tübingen, Tübingen, Germany;3. Geological Survey of Canada-Atlantic, Dartmouth, N.S. & Earth Science Department, Dalhousie University, Halifax, N. S., Canada |
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| Abstract: | The 12 May 2008 Ms 8.0 Wenchuan earthquake, China, was one of largest continental thrusting events worldwide. Based on interpretations of post-earthquake high-resolution remote sensing images and field surveys, we investigated the geometry, geomorphology, and kinematics of co-seismic surface ruptures, as well as seismic and geologic hazards along the Longmen Shan fold-and-thrust belt. Our results indicate that the Wenchuan earthquake occurred along the NE–SW-trending Yingxiu–Beichuan and Guanxian–Anxian faults in the Longmen Shan fold-and-thrust belt. The main surface rupture zones along the Yingxiu–Beichuan and Guanxian–Anxian fault zones are approximately 235 and 72 km in length, respectively. These sub-parallel ruptures may merge at depth. The Yingxiu–Donghekou surface rupture zone can be divided into four segments separated by discontinuities that appear as step-overs or bends in map view. Surface deformation is characterized by oblique reverse faulting with a maximum vertical displacement of approximately 10 m in areas around Beichuan County. Earthquake-related disasters (e.g., landslides) are linearly distributed along the surface rupture zones and associated river valleys.The Wenchuan earthquake provides new insights into the nature of mountain building within the Longmen Shan, eastern Tibetan Plateau. The total crustal shortening accommodated by this great earthquake was as much as 8.5 m, with a maximum vertical uplift of approximately 10 m. The present results suggest that ongoing mountain building of the Longmen Shan is driven mainly by crustal shortening and uplift related to repeated large seismic events such as the 2008 Wenchuan earthquake. Furthermore, rapid erosion within the Longmen Shan fold-and-thrust belt occurs along deep valleys and rupture zones following the occurrence of large-scale landslides triggered by earthquakes. Consequently, we suggest that crustal shortening related to repeated great seismic events, together with isostatic rebound induced by rapid erosion-related unloading, is a key component of the geodynamics that drive ongoing mountain building on the eastern Tibetan Plateau. |
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