Title: Co-seisimic Surface Rupture and Dextral-slip Oblique Thrusting of the M_S 8.0 Wenchuan Earthquake
Abstract:At 2:28 pm, 12 May 2008, the MS 8.0 Wenchuan earthquake struck the Longmenshan area, the eastern margin of the Tibetan Plateau in Sichuan, China. Besides the huge casualties and property losses, a mos...At 2:28 pm, 12 May 2008, the MS 8.0 Wenchuan earthquake struck the Longmenshan area, the eastern margin of the Tibetan Plateau in Sichuan, China. Besides the huge casualties and property losses, a most complicated yet longest thrust-type co-seismic surface rupture zone was developed in the quake-hit area. Field surveys indicate that the Wenchuan earthquake produced at least two NE-trending NW-dipping surface rupture faults on the Longmenshan fault: Yingxiu-Beichuan fault and Guanxian-Anxian faults. The former about 275 km of surface rupture is characterized by dextral-slip thrusting, with a maximum vertical displacement of 11 m and a dextral-slip displacement of 12 m. The latter about 80 km of surface rupture is characterized by pure thrusting, with a maximum vertical displacement of 4 m. Furthermore, the earthquake also produced a 6 km-long NW-trending Xiaoyudong rupture zone, located at the Yingxiu-Beichuan and the Hanwang rupture zones, and characterized by sinistral-slip thrusting. Surface ruptures occur generally along the previous active faults and raise the elevated landforms again, indicating that earthquakes in the Longmenshan region had repeatedly occurred on the same fault belt and accumulation of numerous earthquakes including strong events like the MS 8.0 Wenchuan earthquake result in the formation of the present Longmenshan Mountains. The analysis of the co-seismic fault planes and striation reveals the Wenchuan earthquake is the compound result of two rupture processes. Thrusting and dextral strike-slip dominates the early and later stages, and this is in agreement with the results of seismic wave inversion (Chen et al., 2008; Ji, 2008; Wang et al., 2008). The southern segment of the surface rupture zone (Yingxiu-Qingping segment) suggests two different processes, while the northern only reflects the second event. By comparing the long-term slip rate with the co-seismic displacement, it is estimated that the recurrence intervals of great earthquakes like the MS 8.0 Wenchuan earthquake can be 3000~6000 years. The comparative researches on the West Kunlun, the Altun, the East Kunlun and the Longmenshan Mountains reveal that the similar transpressional structural features -the oblique thrusting -is the dominative mechanism for uplift of surrounding mountains in the Tibetan Plateau.Read More
Publication Year: 2008
Publication Date: 2008-01-01
Language: en
Type: article
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Cited By Count: 26
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