Geo-hazards in Wenchuan quake-hit area: fresh scars,future perils and reconstruction challenges
On Monday, 12 May 2008, a devastating megaearthquake of magnitude 8.0 struck the Wenchuan area, northwestern Sichuan province, China. Fatalities approaching a total 15 thousand occurred, with a significant number resulting from four types of seismically triggered geohazards--rock avalanches and landslides, landslide-dammed lakes (earthquakelakes), and debris flows. China Geological Survey has identified 4 970 potentially risky sites, 1 701 landslides, 1 844 rock avalanches, 515 debris-flows and 1 093 unstable slopes. Rock avalanches and landslides caused many fatalities directly and disrupted the transportation system, extensively disrupting rescue efforts and thereby causing additional fatalities. Landslide-dammed lakes not only flooded human habitats in upstream areas but also posed threats to potentially inundated downstream areas with large populations. Debris flows become the most remarkable geo-hazards featured by increasing number, high frequency, and of low triggering rainfall. Earthquake-triggered geohazards sequentially induced and transformed to additional hazards. For example, debris flows occurred on rock avalanches and landslides, followed by landslide-dammed lakes, and then by additional breakouts of the landslide-dammed lakes and downstream flooding. Earthquake-induced geohazards occurred mainly along the fault zone and decreased sharply with distance from fault. It can be anticipated that post-earthquake geohazards, particularly for debris flows, will continue for 5-10 years and even for as long as 20 years. The 3 key points, regional hazard assessment, individual risk identification and reasonable strategy for disaster mitigation, should be understood before or during reconstruction. Based on the data of remote sensing interpretation, field investigation, disaster survey and digital maps, a hazard degree index model for assessing geo-hazards is established according to disaster-forming factors and seismic parameters. The results show that the high risky zone covers 20 counties and 90 villages and towns with the area of 7691.64km2, accounting for 10.5% of the severely-affected areas; and the moderate risky zone covers 20 counties and 205 villages and towns with the area of 20385.2km2, accounting for 27.7% of the severely-affected areas. The risky assessment can serve for the post-quake reconstruction. An integrated strategy of reconstruction is required. The lesson from Wenchuan earthquake is that the resulted geohazards may appear in large number in active fault regions. A plan for geohazard prevention in the earthquakeactive mountainous areas is needed in advance.
Peng Cui Xiao-qing Chen Yong-shun Hang Jian-qi Zhuang
The Key Laboratory of Mountain Hazards and Earth Surface Process,CAS,Chengdu,China Institute of Mountain Hazards and Environment,CAS,Chengdu,China
国际会议
International Symposium and The 7th Asian Regional Conference of IAEG(国际工程地质与环境协会年会暨第七届亚洲工程地质会议)
成都
英文
113-123
2009-09-09（万方平台首次上网日期，不代表论文的发表时间）