Abstract
Abstract. Because of over-exploration of groundwater for a long time, Jiaxing region, northeast of Zhejiang province has suffering serious ground subsidence during the past several decades. In this paper, we investigate the time series InSAR technique for the generation of subsidence maps over Jiaxing region. 25 ENVISAT ASAR images acquired from Jan 2006 to Aug 2010 are used. The results show that serious subsidence has taken place in Xiuzhou district, Jiashan county, Pinghu county and Haiyan county. 4 subsidence centers, namely Huanggu town in Pinghu, Wangjiangting town in Xiuzhou, Tianning townin Jiashan, and Wuyuan town in Haiyan. 3 obvious subsidence belts are distributed in Jiaxing. Meanwhile in Tongxiang county, Haining county and Nanhu district, there is relatively seldom subsidence. The results are compared with 35 levelling measurements. The standard deviation of the error between the two data is 4.25 mm/year, which demonstrate that time series InSAR technique has good accuracy for subsidence monitoring in Zhejiang province, southeast of China, covered with lots of vegetation and waters.
Highlights
Ground subsidence of Jiaxing began in the urban area in 1964 and it experienced a stage of formation and slow, remarkable and dramatic development
The land area of Jiaxing city is 3915 square kilometers, while as of 2009, the subsidence area has more than 3300 square kilometers with accumulative subsidence above 100 mm. subsidence center has been transferred from Jiaxing old urban area to Wuyuan town, Haiyan county
For long term deformation, conventional 2-pass or 3pass differential interferometric SAR (DInSAR) can be affected by temporal or geometric de-correlation which degrades the interferometric phase and makes it difficult to extract useful information (Ferretti 1999). Some advances in this field have been introduced based on point target analysis, including permanent scatterers (PS) method (Ferretti 2000 and 2001, Vilardo 2009, Zhang 2011), small baseline subsets (SBAS) method (Berardino 2002, Casu 2008) and coherent points (CP) method (Mora 2003, Wu 2011, Zhang 2012)
Summary
Ground subsidence of Jiaxing began in the urban area in 1964 and it experienced a stage of formation and slow, remarkable and dramatic development. Traditional ways of monitoring ground deformation are leveling and GPS measurement They have the advantage of high accuracy. For long term deformation, conventional 2-pass or 3pass DInSAR can be affected by temporal or geometric de-correlation which degrades the interferometric phase and makes it difficult to extract useful information (Ferretti 1999). To solve this problem, some advances in this field have been introduced based on point target analysis, including permanent scatterers (PS) method (Ferretti 2000 and 2001, Vilardo 2009, Zhang 2011), small baseline subsets (SBAS) method (Berardino 2002, Casu 2008) and coherent points (CP) method (Mora 2003, Wu 2011, Zhang 2012). We investigate the small baseline time series InSAR technique for the generation of deformation maps of this city. 25 ENVISAT ASAR images acquired from Jan 2006 to Aug 2010 are used
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