| Summary: | Land subsidence is defined as a gradual settling or sudden sinking of the Earth's surface due to movement of earth materials. Common cause of land subsidence from human activity is groundwater extraction. In Kelantan catchment, groundwater is a vital resource for urban and rural residential, agricultural and commercial water users. Approximately 70% of the total domestic water supplies in Kelantan are from groundwater. Therefore, this study aims to monitor land subsidence due to groundwater extraction using Persistent Scatterer (PS) InSAR. The specific study areas are limited to three prominent groundwater extractions in Kelantan, i.e. Pintu Geng, Tanjung Mas and Tumpat. PSInSAR is an extension to the conventional InSAR techniques, which addresses and overcomes the major limitations of repeat pass SAR interferometry (i.e., temporal and geometrical decorrelation and variations in atmospheric conditions). PSInSAR technique requires only selective pixels which are stable in phase throughout the acquisition time period of the images. Practically, phase stable (PS) pixels are represented by the static ground object such as buildings, roads, bare rocks, bridges and so on. Stanford Method for Persistent Scatterers (StaMPS) was used to identify the PS points and extract deformation signals even in the absence of bright scatterers. This study applies 17 ERS-2 scenes in the descending tracks from April 1996 to February 2011. To verify the deformation rate of the study area, GPS measurements collected at GETI station was compared. The hydrogeological map by the Minerals and Geoscience Department Malaysia (JMG) was used to support in analysis. The results found that the land subsidence rate at Pintu Geng, Tanjung Mas and Tumpat is about -1.78 mm/yr, -2.39mm/yr and -1.87mm/yr respectively. Extensive land subsidence due to groundwater extension is existed in the study area and thus this concludes that the PSInSAR application is suitable for monitoring land subsidence.
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