## 1 Introduction  
The Leizhou Peninsula (LZP), one of the three largest peninsulas in China, is located in the southwest of Guangdong province, China, covering an area of 8500 km\({}^{2}\)[1] (see Figure 1). It plays an important role in the economic development of Guangdong province with its considerable agriculture contributions. However, over the past two decades the fast growing economy has accelerated groundwater over-pumping, causing large scale land subsidence and other geological hazards. Until 2001, the subsidence area in Zhanjiang city reached 220 km\({}^{2}\), with the maximum cumulative subsidence up to 17.9 cm [2]. Subsidence induced geological hazards have resulted in substantial property damage every year. For example, in 2006 only, the loss in Zhanjiang city was greater than 90 million RMB [3]. However, large-scale land subsidence measurement is still scarce in the LZP apart from a few leveling measurements carried out in the urban area of Zhanjiang city in 1984, 1989, 1999, and 2001, whose results indicated that the surface subsidence increased by \(>\)10 mm/year [2,4]. A surface deformation map presenting the temporal-spatial pattern of land subsidence of the whole peninsula is urgently needed to help the government make the right decisions in geological disaster prevention and mitigation, as well as to understand the mechanism of land subsidence caused by over-pumping groundwater.  
Interferometric Synthetic Aperture Radar (InSAR), a satellite based technique, offers high precision (cm even to mm), high spatial resolution, and wide coverage measurements of surface deformation, reducing the use of in-situ traditional techniques [5; 6]. Furthermore, with the development of the SAR satellite missions, more and more newly acquired TerraSAR, COSMO-SkyMed, Sentinel-1, ALOS-2 and archived SAR data (ERS1/2, JERS-1, ENVISAT, ALOS1) can be used to analyze the spatial-temporal characteristics of large area surface deformation with the temporal InSAR technique [7]. Therefore, the InSAR technique can serve as a good option in mapping the surface deformation of a large-scale area. Actually, it has been widely used and its superiorities shown in detecting time-series surface deformation over many peninsulas and delta areas, such as the Mexico City [8], Shanghai [9], and Indonesia [10]. Traditional temporal InSAR methods, such as Persistent Scatterer Interferometry (PS-InSAR), IPTA (Interferometric Point Target Analysis), and Small Baseline Subset (SBAS-InSAR) have been applied in detecting surface deformation, but they need abundant SAR images in data processing [11; 12; 13]. As the datasets are very limited in our study area, we used a modified stacking method to measure the surface deformation evolution over the whole LZP with three kinds of SAR images (JERS, ENVISAT and ALOS1) acquired from 1992 to 2010. Based on those results, the reasons and mechanisms of land subsidence can be explained and are investigated in this study.  
Here, we map the surface deformation of three different sensor platforms and illustrate the spatial-temporal evolution patterns in urban and agriculture areas. Based on the surface hydrogeological and land use, we analyze the reason for land subsidence. The consequences and implications of our land subsidence measurement are discussed in the last section.