avalanches, landslides and quake lakes induced by the
Wenchuan Earthquake on May 12, 2008
Zhaoyin Wang1)
(Professsor, State Key Lab of Hydroscience and Engineering, Tsinghua University,
Beijing 100084, China, Email: zywang@tsinghua.edu.cn)
1. Wenchuan earthquake
A great earthquake measured at 8.0 Ms according to the China Seismological Bureau occurred at Wenchuan (31°01′16″N, 103°22′01″E ) at 14:28 May 12, 2008 (Beijing time), 80 km northwest of Chengdu, the capital of Sichuan, with a depth of 19 km. The epicenter is at Yingxiu of the Wenchuan county. According to a report by the state government of China on July 31, 2008, the earthquake killed 68,197 people, injured 374,176 people and left 18,222 missing. According to the British Geological Survey, seismicity in the region is caused by the northward movement of the Indian Plate at a rate of 5 cm/year and its collision with the Eurasian Plate, resulting in the uplift of the Himalaya and the Qinghai–Tibetan plateau and associated earthquake activity (Wikipedia, 2008). This deformation also results in the extrusion of crustal material from the high plateau in the west towards the Sichuan Basin and southeastern China. The earthquake was felt as far away as Beijing (1,500 km) and Shanghai (1,700 km). The earthquake occurred as a result of motion of the Qinghai–Tibet plateau at Longmenshan Mountain along the Yingxiu–Qingchuan fault, as shown in Fig. 1. More than 100 major aftershocks, ranging in magnitude from 4.0 to 6.1, were recorded. The quake-hit area is about 440,000 km2.
There are many streams in the quake-hit area, which deeply cut the mountains. Figure 1 shows the streams on the east margin of the Qinghai–Tibet Plateau and the locations of 33 quake lakes created by landslides during the Wenchuan earthquake. The Minjiang, Tuojiang, Fujiang and Jialing Rivers are tributaries of the Yangtze River. Other streams are tributaries of the four rivers. The quake lakes are mostly on these streams. Because the Qinghai–Tibet plateau is rising, most of the tributaries flow into the four major rivers from the west side (right side). The Longmenshan fracture belt consists of three faults: in the middle is the major Longmenshan fault, where the Wenchuan earthquake occurred, extends from Yingxiu to Qingchuan, on the left side there are two broken faults called the back fault, and on the right side there are two broken faults called the front fault. The streams in the area are incised channels and the bank slopes are so steep that slope failures readily occur during rainstorm and earthquake events.
.....
FULL PAPER (pdf file, 1.0 MB)