四川汶川大地震震害遥感调查与评估

Investigation and Assessment of Damage in Earthquake Wenchuan Sichuan Quake Based on Remote Sensing

回顾了中国应用遥感技术调查评估地震灾害的历史及其进展,经过综合论证,给出了汶川地震5种震害的分类划分标准和灾害遥感调查评估总体技术流程,总结了灾害遥感调查评估各个不同阶段,采用不同遥感信息源和不同遥感技术方法识别不同震害的效果,为汶川特大地震灾中救援和灾后重建提供了决策依据;结合遥感技术发展的趋势和地震灾害的特点,提出了震害遥感调查评估的发展趋势。

Earthquake is one of the most destructive natural disasters in China.For a long time,investigation of earthquake damage has been based on field surveys,but disadvantages of this means,such as huge workload,low efficiency,too much expense and un-visualized information,make it not practical.However,remote sensing technique can provide a rapid and effective approach for quick investigation and assessment of earthquake damage,owning to its characteristics of objectivity,real-time and macro-scope view.The history of investigation and assessment of earthquake damage based on remote sensing in China: Since mid of 1960s,institutes and departments of Chinese Academy of Sciences have done a lot of work on quake damage investigation and assessment and accumulated rich experience.Aerial photography was carred out for Xingtai quake in 1966,Haicheng earthquake in 1975,Tangshan quake in 1976 and Lancang-Gengma earthquake in 1988 and the mornitoring and mapping for earthquake damage were accomplished in different scales.All of these achievements provided important scientific basis for decision-making of the earthquake relief and reconstruction.With the development of remote sensing technique for decades,this technology supplies technical support and priori knowledge for the investigation and assessment of Wenchuan quake damage.There occurred open ended Richter 8.0 scale earthquake in the county of Wenchuan,Sichuan province on May 12th,2008,which has caused huge destructive losses.In this,the remote sensing technique is used to investigate and paper assess the situation of the earthquake damage.There are five classes of features which can be interpreted according to the remote sensing imageries:(1) the damage degree of buildings,like civilian homes,factories,schools,hospitals and so on,which is related to the safety of human life and property directly;(2) the damage degree of structures,such as television towers,chimneys,oil tanks,power houses and etc.,which can indicate the intensity of the earthquake;(3) the damage degree of the lifeline,for example,the highway,railway,bridge,power and communication supply,which are very important for disaster relief and human's life after the earthquake;(4) the field disasters of earthquake,such as landslides,debris flows,ground fissures;(5)the secondary disasters caused by field disasters,like quake lakes,emission of harmful gases.All of these five classes of features are the main data for determinating the intensity of earthquake and the degree of damage.The features can be obtained according to different spectral and spatial resolution of remote sensing imageries,through image processing and interpretation methods.Besides,other kinds of data can also be imported for assistant interpretation.The work flow includes remote sensing image processing,human-machine interactive classification,location,qualitative and quantitative information extraction,GIS-support assessment of earthquake damage,mapping of damaged objects.In this study,the radar images are used.Due to the bad weather after the earthquake,and the optical remote sensing cannot get useful information.As a result,the all-weather radar sensor can provide lots of information and the 1m spatial resolution radar images have played an important role in the investigation.Certainly,the optical remote sensing imageries also played an important role.Using kinds of remote sensing images,the abundace of landslides,collapse debris flows,the rate of building damages,the situation of quake lakes and road damage are interpreted.In conclusion,remote sensing technique can play an important role in the investigation and assessment of earthquake damage.Of course,remote sensing application in WenChuan quake shows some shortcomings,and it may be improved and developed in five aspects as follows.(1) It is important to select imageries and high spatial resolution imageries are significant.(2) The basic database is needed to be built.(3) Quick interpretation techniques should be developed.(4) It is more practical to use human-computer interactive interpretation extract earthquake information.(5) In investigation of earthquake damages,data process techniques of 3D rebuild will quickly be developed and remote sensing,GIS and GPS techniques will be combined and applied to the investigations in wider and higher level.