ABSTRACT

A strong earthquake of Ms 8.0 happened on 12 May 2008 in Wenchuan, Sichuan Province, China. The secondary geologic hazards were very serious. Wenchuan geohazards investigation team organized by Chinese academy of sciences entered into Wenchuan to carry out the post-earthquake geohazards investigation in October 2008. Based on the investigation, the paper discusses the geological background of Wenchuan earthquake, the basic characteristics of secondary geohazard and its development trend. Some suggestions are put forward for the postearthquake reconstruction in disaster area.

1 INTRODUCTION

A strong earthquake of Ms 8.0 happened on 12 May 2008 in Wenchuan, Sichuan Province, China. The secondary geohazards were so serious that it damaged not only the huge amounts of buildings, farmlands, traffic and casualties, but also hindered Chinese urgent rescue work. It is noteworthy that collapse hazard was one of the most widely distributed geological disasters. It distributed widely and had the different scale. Whenever the latent collapse incidents may happen because of the fragmentation of mountains triggered by the earthquake. It is very necessary and urgent to strengthen the scientific research on the forming mechanism and dynamic process of collapse triggered by the earthquake.

Our China is a multi-earthquake country. There were many strong earthquakes occurring in history. The earthquake which is one of the severest natural disaster threats is in seismic active period. Also our China is a mountainous country, in which hilly and mountainous areas account for two-thirds of the whole land areas. There is massive earthquake fault zone development in most areas and the most active seismic zones are in the alpine gorges, such as Longmenshan frature. So it is very outstanding of the secondary geological hazards triggered by the earthquake. Wenchuan geohazards investigation team organized by Chinese academy of sciences entered into Wenchuan to carry out the post-earthquake geohazards investigation in October 2008.

2 GEOLOGICAL BACKGROUND AND BASIC CHARACTERISTICS OF WENCHUAN EARTHQUAKE

The basic generation reason of Wenchuan strong earthquake is that the strong broaching force transferred to Longmen mountain fault zone in the west of Sichuan basin from Tibetan plateau because of the sustained broaching effect between Indian plate and Eurasia plate. The sustained accumulation of stress and energy producing in this area was finally more than the affordability of central main fracture in Longmenshan fault zone. So that the long-term strain energy accumulation formed the huge earthquake (Runqiu Huang, 2008). The structural deformation of continental lithosphere is a kind of kinetic formulation of bidirectional extension deformation from crustal derm to deep extension and from crust-mantle transition zone to upper crust (Xuelin Cai, 2008).

The earthquake hazards brought out great damage mainly because that seismogenic zone is located in mountain area in the west of Sichuan basin, in which there are extremely vulnerable geological environment, large height difference terrain and relative dense population. The hazards were triggered on the one hand by the earthquake, on the other hand by geohazards

(Plate in full paper)

It is found that the intense activity of secondary geohazards further intensified the risk.

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