Nonlinear Modeling of Subsidence From a Decade of InSAR Time Series

We present a model of ground subsidence due to soil consolidation within coastal reclaimed land constructed in early 2001, in Busan, South Korea. We estimate 42 cm of maximum subsidence during the period of interferometric synthetic aperture radar observations, and a maximum of 1 m or more subsidence, since the end of the construction phase of the reclamation project. A hyperbolic model was used to relate the three independent time series and to estimate the nonlinear behavior of subsidence. The model estimates a maximum subsidence rate and acceleration of -5.7 cm/year and 1.1 cm/year(2), respectively. The decomposition of vertical and east-west horizontal motion using the Sentinel-1 dataset indicates relatively weak partial horizontal displacement as well as substantial vertical deformation overall. The long-term time series analysis indicates ongoing ground subsidence, although almost two decades have passed since the completion of reclamation. Plain Language Summary Ground subsidence is a process that may threaten human lives and property, and it often occurs owing to the compaction of alluvial sediments as a result of groundwater extraction or soil consolidation. In particular, coastal reclaimed land composed of soft materials such as sand or soil, rather than massive rock, is vulnerable to subsidence. We used three data sets comprising interferometric radar images from two satellites to monitor ground subsidence over time in Busan, South Korea, from 2007 to 2019. We noted not only vertical surface displacement in the overall area, which was expected, but also local displacement in the horizontal direction in specific areas. A hyperbolic model was used to estimate the vertical movement over time due to subsidence, instead of a constant subsidence model. The model results indicate ongoing ground subsidence in the study area, although almost 20 years have passed since the completion of reclamation.

Automated summary

Our study in Busan, South Korea, revealed ongoing ground subsidence in coastal reclaimed land since 2001, with a maximum subsidence rate and acceleration estimated using a hyperbolic model. Decomposition of vertical and horizontal motion indicated both weak horizontal displacement and significant vertical deformation. Despite almost two decades passing since the reclamation project completed, ground subsidence continues to occur.