In February 2023, Mw 7.8 and Mw 7.7 earthquakes struck southeastern Turkey. Generating a coseismic 3D deformation field that can directly reflect the characteristics of surface deformation is important for revealing the movement mode of a seismogenic fault and analyzing the focal mechanism. Optical image sub-pixel correlation (SPC) only captures deformation in the horizontal direction, and SAR image pixel offset tracking (POT) obtains range deformation that is not sensitive to north–south deformation signals. Thus, neither of them can capture the complete 3D deformation alone. Combining them may be able to allow the monitoring of 3D deformation. In this study, we used Sentinel-2 optical images to obtain the horizontal deformation (east–west and north–south) and Sentinel-1 and ALOS-2 data to extract the range and azimuth offsets. The least-squares method was used to fuse the optical and SAR offsets to obtain the 3D deformation field of the 2023 Turkey earthquake sequence, which indicates that the two events were both left-lateral strike-slip earthquakes. The surface deformation caused by the two large earthquakes is mainly in the east–west direction. In the vertical direction, the two earthquakes caused a small-magnitude uplift and subsidence. The findings in this paper can be used as a reference for the study of coseismic 3D deformation.

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This study monitors the land subsidence of the whole Pearl River Delta (PRD) (area: ~40,000 km2) in China using the ALOS1/PALSAR data (2006-2011) and the SBAS-InSAR method. We also analyze the relationship between the subsidence and the coastline change, river distribution, geological survey data as well as the geomorphology data. The results show that (1) the land subsidence with the average velocity of 50 mm/year occurred in the low elevation area in the front part of the delta and the coastal area; (2) the areas along rivers also suffered from surface subsidence, due to the fragile geological structure and frequent human interference; (3) the geological evolution is the intrinsic factor of the surface subsidence in the PRD, but human interference (reclamation, ground water extraction and urban construction) extend the subsiding area and accelerate the subsiding rate. This study would provide technique supports for the surface deformation and disaster warning in delta regions.

This study monitors the land subsidence of the whole Pearl River Delta (PRD) (area: ~40,000 km2) in China using the ALOS1/PALSAR data (2006-2011) through the SBAS-InSAR method. We also analyze the relationship between the subsidence and the coastline change, river distribution, geological structure as well as the local terrain. The results show that (1) the land subsidence with the average velocity of 50 mm/year occurred in the low elevation area in the front part of the delta and the coastal area, and the area of the regions subsiding fast than 30 mm/year between 2006 and 2011 is larger than 122 km2; (2) the subsidence order and area estimated in this study are both much larger than that measured in previous studies; (3) the areas along rivers suffered from surface subsidence, due to the thick soft soil layer and frequent human interference; (4) the geological evolution is the intrinsic factor of the surface subsidence in the PRD, but human interference (reclamation, ground water extraction and urban construction) extends the subsiding area and increases the subsiding rate.