Study of land subsidence by radar interferometry and hot spot analysis techniques in the Peshawar Basin, Pakistan

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Land subsidence caused by anthropogenic activities is frequently reported in many megacities worldwide, affecting over 500 million residents. For the first time, this work is reporting substantial ground subsidence in the fifth largest city of Pakistan. Observation of surface deformation using the Small Baseline Subset (SBAS), Interferometric Synthetic Aperture Radar (InSAR) technique on Sentinel-1A datasets from 2015 to 2019 show subsidence up to 3.23 cm. Geologically, this region is going through active deformation associated with Himalayan orogeny. From August 1973 till December 2018, around ten thousand low- to moderate-magnitude earthquakes are reported.We used the emerging hot spot analysis on InSAR and earthquake data to assess the role of seismicity on subsidence. Four variables were analyzed; ground displacement measured by InSAR, earthquake count, earthquake depth, and earthquake magnitude. Analysis of InSAR data indicates that the vast majority of the area is subsiding. This investigation also reveals that earthquake activity near Peshawar is decreasing. In contrast, the earthquake activity is unstable but high in the direction of Tarbela Dam, which is the world's largest earth-filled dam.No systematic groundwater monitoring program has been implemented, and limited published data suggest that the water demand quadrupled in the last decade. A decline in the water table is also reported. Optimized hot spot analysis of water pumping data for 2017 shows a few isolated mild hot spots in the urban center. Excessive groundwater demand and Land-use change from agriculture to urban may have played a significant role in land subsidence in this region.