The Preliminary Result on Persistent Scatters and Corner Reflectors Differential Interferometry in Three Gorges Area

Qiming Zeng(1) , Jingfa Zhang(2) , Zhuxi Ouyang(3) , Huaiping Xue(4) , Jan-Peter Muller(5) , and Zhenhong Li(5)

(1) Peking University, Beijing, 100871, China
(2) China Seismological Bureau, Beijing, 100871, China
(3) China Seismological Bureau, Beijing, 100871, China
(4) Chinese Academy of Science, Wuhan, 430000, China
(5) University College London, Gower Street, London - WC1E 6BT, United Kingdom

Abstract

The Three Gorges Dam is the biggest hydraulic engineering on the world, which is started to fill water since June of 2003 up to water level of 135 meter, and will finish in 2007, the full water level is designed up to 175 meter. The reservoir of the Three Gorges with length over 600 kilometers and average width of 1100 meters appears, the total area of the reservoir is about 1084 square kilometers. In this area, along with rise of water level, the hydrogeological and stress condition is changing, the earthquakes and landslides frequently occur. The records of observation indicate there are more than 1000 small earthquakes (less than Ms 2) in this area in past two years. Just in 2004, there are over 16 landslides has been predicted by local traditional observation network and GPS monitoring network in the area. These methods have disadvantages of low spatial and temporal resolution, human power and money consume. Differential Interferometry SAR (DInSAR) has capability of high spatial and temporal resolution to measure small surface deformation. However, in Three Gorges Area, steep topography, dense vegetation cover and frequent stochastic changing cloud would be great challenge to DInSAR. Persistent Scatters (PS) InSAR is a promising method to measure slow and small subsistence in urban area, which explore high density PS points (about 40~120 points per square kilometer) in at least 30 SAR images. It is difficult to find out enough PS point in this area. We have setup 30 traditional trihedral corner reflectors (CR) to complement natural PSs in 2003. This paper would like to report preliminary result of Dragon Project “Monitoring Landslides in the Three Gorges Area Using Corner Reflector Differential SAR Interferometry” (Dragon Project ID 2558). Following the methods of PS InSAR, we have identified some natural PS point in two test areas, and combined with CRs recognized, and differential phase for these points have been retrieved and analysis. With the help of MERIS data synchronous acquired, we have made atmospheric phase correction to obtain pure deformation phase for these points.

 

 

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