S1-PSINSAR MONITORING AND HYPERBOLIC MODELING OF NONLINEAR GROUND SUBSIDENCE IN NAGA CITY, CEBU ISLAND IN THE PHILIPPINES
Keywords:Sentinel-1 PSInSAR, Ground deformation monitoring, Hyperbolic model, Coastal city, Cebu Island
Human activities are increasingly altering subsurface conditions leading to unwanted ground deformations. Excessive ground deformations endanger buildings, linear systems, underground facilities, and, ultimately, people’s safety. Thus, mapping and monitoring ground deformation are critical in managing disaster risk and mitigating socio-economic damage from possible geohazards. Accessible and archived satellite data and the continual development of advanced remote sensing technologies can now provide valuable information about the earth’s surface for various applications. This study applied the descending Sentinel-1 Persistent Scatterer Interferometric Synthetic Aperture Radar (S1-PSInSAR) technique for long-term remote ground deformation monitoring over the coastal city of Naga in Cebu Island in the Philippines. The S1-PSInSAR technique provided relatively dense ground monitoring points, specifically over built-up areas. The maximum ground subsidence along the radar line-of-sight (LOS) estimated throughout the monitoring period from October 2014 to September 2018 exceeds –50 mm, whereas the LOS mean displacement velocity exceeds –15 mm/yr. The two-parameter hyperbolic model well fitted the S1-PSInSAR results to describe the ground deformation’s non-uniform and nonlinear behavior. Ground deformation over the coastal city continues to evolve, and stabilization is yet to occur. This study suggests that the S1-PSInSAR technique and the hyperbolic function can provide technical support in mapping, monitoring, and (or) forecasting ground deformation over vast areas with less human labor and efficient cost.