The Longmenshan Fault is a thrust fault

Thrust fault

A thrust fault is a type of fault, or break in the Earth's crust across which there has been relative movement, in which rocks of lower stratigraphic position are pushed up and over higher strata. They are often recognized because they place older rocks above younger...

 which runs along the base of the Longmen Mountains

Longmen Mountains

The Longmen Mountains , also tautologically referred to in English-language publications as the Longmenshan Mountains, are a mountain range in Sichuan province in southwestern China.-Geography:...

 in Sichuan

Sichuan

' , known formerly in the West by its postal map spellings of Szechwan or Szechuan is a province in Southwest China with its capital in Chengdu...

 province in southwestern China

China

Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

. The strike of the fault plane is approximately NE.
Motion on this fault is responsible for the uplift of the mountains relative to the lowlands of the Sichuan Basin

Sichuan basin

The Sichuan Basin is a lowland region in southwestern China. Despite its historical name, it is not only synonymous to Sichuan province, comprising its central and eastern portions as well as part of Chongqing Municipality...

 to the east. Representing the eastern boundary of the Qinghai-Tibet Plateau

Tibetan Plateau

The Tibetan Plateau , also known as the Qinghai–Tibetan Plateau is a vast, elevated plateau in Central Asia covering most of the Tibet Autonomous Region and Qinghai, in addition to smaller portions of western Sichuan, southwestern Gansu, and northern Yunnan in Western China and Ladakh in...

, it is a border formation between the Bayan Kola block in the Plateau and the South China block in the Eurasian Plate

Eurasian Plate

The Eurasian Plate is a tectonic plate which includes most of the continent of Eurasia , with the notable exceptions of the Indian subcontinent, the Arabian subcontinent, and the area east of the Chersky Range in East Siberia...

. The 2008 Wenchuan earthquake

2008 Sichuan earthquake

The 2008 Sichuan earthquake or the Great Sichuan Earthquake was a deadly earthquake that measured at 8.0 Msand 7.9 Mw occurred at 14:28:01 CST...

 occurred along this fault.

A study by China Earthquake Administration (CEA) states:

"The late-Cenozoic deformations in this fault (that caused the 2008 Wenchuan earthquake) are concentrated in the Guanxian-Jiangyou

Jiangyou

Jiangyou is a Chinese county-level city located in Mianyang, Sichuan. The city proper is subdivided into four urban districts and has jurisdiction over 21 towns, and 19 rural townships...

 fracture (hill-front fracture), Yingxiu-Beichuan fracture (mid-fracture), Wenchuan-Mao County

Mao County

Mao County is a county in Ngawa Prefecture, Sichuan Province, China.It has an area of 3,903 and a population of 106,700 as of 2006. 88.9% of the population are Qiang people...

 fracture (hill-back fracture), and their related folds. The recent M_s 8.0 earthquake occurred on the Yingxiu-Beichuan fracture, as a result of Longmenshan thrust pushing southeastward combined with clockwise shears.

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."

Morphology

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

Tibetan Plateau

The Tibetan Plateau , also known as the Qinghai–Tibetan Plateau is a vast, elevated plateau in Central Asia covering most of the Tibet Autonomous Region and Qinghai, in addition to smaller portions of western Sichuan, southwestern Gansu, and northern Yunnan in Western China and Ladakh in...

 is one of the world's most remarkable continental escarpments. Elevations rise from circa 600 m in the southern Sichuan Basin

Sichuan basin

The Sichuan Basin is a lowland region in southwestern China. Despite its historical name, it is not only synonymous to Sichuan province, comprising its central and eastern portions as well as part of Chongqing Municipality...

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."

External links

• Map of faults in SW China - MIT
• University of Arizona
• Simplified geologic map of the Longmen Shan region of the eastern margin of the Tibetan Plateau.
• China Virtual Museum of Earthquakes, map charting the Five Seismic Belts in China