SAR remote sensing monitoring of the Yushu Earthquake disaster situation and the information service system

Earthquake is one of most serious natural disasters in the world.It has wide geographic coverage,huge damage,and long time influence for recovery.The earthquake happened in Wenchuan on May 12,2008 caused great damage in 42 counties in Sichuan province,23 counties in Gansu province,and 19 counties in Shaanxi province.In addition,it also has much influence on Chongqing,Yunnan,Shanxi,Guizhou,and Hubei provinces.Because of the severely destroyed infrastructures,complicated topography and bad weather condition after the earthquake,the disaster situation assessment from ground investigation is very difficult to undertake.In this situation,feasible approaches should be investigated.In this paper,we take the remote sensing monitoring and assessment of the Wenchuan Earthquake disaster situation as a case study and discuss the technical approaches and methods on application of space and airborne remote sensing technology for earthquake disaster situation monitoring and assessment.Firstly,by integrating multi-platform multi-sensor data,we defined the earthquake disaster situation monitoring indexes according to two different disaster severity levels.For areas with high-level disaster loss,aerial photos and high-resolution satellite images with less than 1 meter resolution are used as the major data sources,where four major categories with detailed subclasses are classified,i.e.,1) urban and rural residential areas;2) urban and rural infrastructures such as industrial and mining lands,highways,railways,bridges,tunnels,electric facilities,telecommunication facilities,channels,dikes,reservoirs,and dams;3) geological and environmental change information such as earthquake lakes,rock slumps,landslides,and turbidities;and 4) destroyed farmlands such as croplands and forest lands.For areas with low-level disaster loss,high and medium resolution optical and SAR satellite images before and after the earthquake are used as the major data sources,where four major categories with less detailed subclasses are classified,i.e.,1) urban and rural residential areas;2) urban and rural infrastructures such as industrial and mining lands,highways,railways,and large reservoirs;3) geological and environmental change information such as earthquake lakes,rock slumps,landslides,and turbidities;and 4) destroyed farmlands such as croplands and forest lands.By combining the multi-temporal,multi-source data before and after the earthquake,we establish the technical flows for quick geometric processing,quick data quality analysis and assessment,quick change detection,quick target interpretation,quick spatial risk assessment for landslides induced by earthquake,and the synthesis of these methods for disaster monitoring.For geometric processing,the ImageInfo software module PixelGrid is used.For image fusion,the data fusion module of ImageInfo is used.For interpretation of different area of images,the ArcGIS software is used.Additionally,the SINMAP module under ArcGIS software is also used for the validation of the extracted geological risk areas.The approach has been successfully applied in monitoring,mapping,and statistical assessment of the earthquake disaster situation.In addition,we also develope an application system which could provide functionalities for disaster information management,visualization,and statistical analysis.It utilize 2D WebGIS user interface and 3D virtual simulation environment to manage the disaster database and visualize the monitored results as 2D maps,statistic tables,graphs,and 3D models,and provide functionalities for measure and analysis.Finally,we also addressed and discussed some practical problems when applying this approach that should be well justified in the future,including the development of new geometric correction algorithm without control points,and the standardization of the workflow described in this paper for better accuracy.