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The 2008 Sichuan earthquake (Chinese: 四川大地震; pinyin: Sìchuān dà dìzhèn), at a magnitude 7.9 Mw, occurred at 14:28:01.42 CST (06:28:01.42 UTC) on 12 May 2008 in Sichuan province of China. In China, it was named the Wenchuan earthquake (Chinese: 汶川大地震; pinyin: Wènchuān dà dìzhèn), after the earthquake's epicenter in Wenchuan County in Sichuan province. The epicenter was 90 kilometres (56 mi) west-northwest of Chengdu, the capital of Sichuan, with a depth of 19 kilometres (12 mi).[2] The earthquake was felt as far away as Beijing (1,500 km away) and Shanghai (1,700 km away), where office buildings swayed with the tremor.[3] The earthquake was also felt in nearby countries.
Official figures (as of 16 May) state that 22,069 are confirmed dead, including 21,577 in Sichuan province.[1][4] The Chinese government warned that the death toll could soar to 50,000.[5] Tens of thousands are missing, many of them buried, and eight provinces were affected.[6][7] It was the deadliest and strongest earthquake to hit China since the 1976 Tangshan earthquake, which killed over 250,000 people.[8]
Earthquake details
The earthquake had a magnitude of 7.8 Ms according to the State Seismological Bureau of China and 7.9 Mw according to the United States Geological Survey. The epicenter was in Wenchuan County (Chinese: 汶川县; Pinyin: Wènchuān Xiàn), Ngawa Prefecture, 75 km west/northwest of Chengdu, with its main tremor occurring at 14:28:01.42 CST (06:28:01.42 UTC), on Monday 12 May 2008.
Fifty-two major aftershocks, ranging in magnitude from 4.4 to 6.0, were recorded within 72 hours of the main tremor.[9] Preliminary rupture models of the earthquake indicated displacement of up to 9 meters along a fault approximately 240 km long by 20 km deep.[10] The earthquake generated deformations of the surface greater than 3 meters[11] and increased the stress (and probability of occurrence of future events) at the northeastern and southwestern ends of the fault.[11]
Office workers in Chengdu reported a "continuous shaking for about two or three minutes", and many people rushed outside.[12]
Tremors felt in different places
China (mainland): All regions except Xinjiang, Jilin and Heilongjiang were affected by the quake.[13]
Bangladesh: Tremors were felt eight and a half minutes after the quake in all parts of Bangladesh.[14]
Hong Kong: Tremors were felt approximately three minutes after the quake, continuing for about half a minute. This was also the farthest distance from the epicentre felt in Hong Kong's record.[15][16][14][17]
India: Tremors were felt approximately nine minutes after the earthquake in parts of India.[14][18]
Japan: Tremors were felt in Tokyo.[18]
Macau: Tremors were felt approximately three minutes after the quake.[19]
Mongolia: Tremors were felt approximately eight minutes after the earthquake in parts of Mongolia.[14]
Nepal: Tremors were felt approximately eight and a half minutes after the quake.[14]
Pakistan: In parts of Northern Pakistan tremors were felt ten minutes after the quake.[14]
Russia: Tremors were felt in Tuva, no casualties reported.[14]
Taiwan: It took about eight minutes for the quake to reach Taiwan, then the tremors continued for one to two minutes; no damage or injuries were reported.[20]
Thailand: In parts of Thailand tremors were felt six minutes after the quake, continuing for 7 to 8 minutes.[18]
Vietnam: Tremors were felt approximately five minutes after the earthquake in Northern parts of Vietnam.[21][22][18]
Tectonics
According to the United States Geological Survey:[23]
The earthquake occurred as the result of motion on a northeast striking reverse fault or thrust fault on the northwestern margin of the Sichuan Basin. The earthquake’s epicenter and focal-mechanism are consistent with it having occurred as the result of movement on the Longmenshan fault or a tectonically related fault. The earthquake reflects tectonic stresses resulting from the convergence of crustal material slowly moving from the high Tibetan Plateau, to the west, against strong crust underlying the Sichuan Basin and southeastern China.
On a continental scale, the seismicity of central and eastern Asia is a result of northward convergence of the Indian Plate against the Eurasian Plate with a velocity of about 50 mm/y. The convergence of the two plates is broadly accommodated by the uplift of the Asian highlands and by the motion of crustal material to the east away from the uplifted Tibetan Plateau. The northwestern margin of the Sichuan Basin has previously experienced destructive earthquakes. The magnitude 7.5 earthquake of August 25, 1933 killed more than 9,300 people.
According to the British Geological Survey:[24]
The earthquake occurred 92 km northwest of the city of Chengdu in eastern Sichuan province and over 1500 km from Beijing, where it was also strongly felt. Earthquakes of this size have the potential to cause extensive damage and loss of life. The epicentre was in the mountains of the Eastern Margin of Qing-Tibet Plateau at the northwest margin of the Sichuan Basin. The earthquake occurred as a result of motion on a northeast striking thrust fault that runs along the margin of the basin. The seismicity of central and eastern Asia is caused by the northward movement of the India plate at a rate of 5cm/year and its collision with Eurasia, resulting in the uplift of the Himalaya and Tibetan plateau and associated earthquake activity. This deformation also results in the extrusion of crustal material from the high Tibetan Plateau in the west towards the Sichuan Basin and southeastern China. China frequently suffers large and deadly earthquakes. In August 1933 a magnitude 7.5 earthquake about 90 km notheast of today's earthquake destroyed the town of Diexi and surrounding villages, and caused many landslides, some of which dammed the rivers.
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