~四川大地震~急~問題分數20分~

Felt Reports

At least 62,000 people killed , 23,000 was still missing and severe damage in the Dujiangyan-Mianzhu-Mianyang area. Landslides blocked roads and buried buildings in the Beichuan-Wenchuan area. Felt (VII) at Chengdu, (VI) at Xi'an and (V) at Chongqing and Lanzhou. Felt in much of central, eastern and southern China, including Beijing, Guangzhou, Nanjing, Shanghai, Tianjin, Wuhan and in Hong Kong. Also felt in parts of Bangladesh, Taiwan, Thailand and Vietnam.

Tectonic Summary

The Sichuan earthquake of May 12, 2008, 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 India plate against the Eurasia 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.