| Longmenshan Fault | |||||||||
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| Chinese | 龙门山断层 | ||||||||
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The Longmenshan Fault (Chinese: 龙门山断层) is a thrust fault which runs along the base of the Longmen Mountains in Sichuan province in southwestern China. The strike of the fault plane is approximately NE.[1] Motion on this fault is responsible for the uplift of the mountains relative to the lowlands of the Sichuan Basin to the east. Representing the eastern boundary of the Qinghai-Tibet Plateau, it is a border formation between the Bayan Kola block in the Plateau and the South China block in the Eurasian Plate. The 2008 Wenchuan earthquake occurred along this fault.[2]
A study by China Earthquake Administration (CEA) states[2]:
"The late-Cenozoic deformations in this fault (that caused the 2008 Wenchuan earthquake) are concentrated in the Guanxian-Jiangyou fracture (hill-front fracture), Yingxiu-Beichuan fracture (mid-fracture), Wenchuan-Mao County fracture (hill-back fracture), and their related folds. The recent Ms 8.0 earthquake occurred on the Yingxiu-Beichuan fracture, as a result of Longmenshan thrust pushing southeastward combined with clockwise shears.[3]
Since Holocene (10,000), Yingxiu-Beichuan fracture has had evident activities. Its long-term geological slip rate is slower than 1 mm per year. GPS observations confirm the current structural deformation of the Longmenshan formation to be characterized by thrust and right-handed shears, but with a low deformation rate. Therefore, Longmenshan formation and its internal fractures constitute a special type that has low earthquake frequences but the potential to cause super strong earthquakes.[4]"
The American Geophysical Union publication Tectonics describes the 5 km high escarpment thus:
"In the Longmen Shan region, however, the topographic margin of the Tibetan Plateau is one of the world's most remarkable continental escarpments. Elevations rise from circa 600 m in the southern Sichuan Basin to peaks exceeding 6500 m over a horizontal distance of less than 50 km. Regional topographic gradients typically exceed 10 % along this mountain front and rival any other margin of the plateau."[5]
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