Horizontal Strain Rate estimation from InSAR Observations and the Strapdown Method

Alexandru Mihai Lapadat, Ramon Hanssen 

Interferometric Synthetic Aperture Radar (InSAR) is able to estimate ground-surface displacements, but interpreting deformation mechanisms and infrastructure risk requires analysis of spatial displacement gradients. The recently introduced strapdown method enables three-dimensional displacement velocities to be estimated from InSAR observations alone, including the east and north components required for horizontal strain-rate analysis. Here, we present an approach that inverts these east and north velocity components using a finite-element framework to estimate a continuous horizontal velocity field and subsequently derive the horizontal strain-rate tensor and other deformation metrics with quantified uncertainties. Applied to Jakarta, these results show that horizontal strain-rate analysis can distinguish between two distinctly different mechanisms driving subsidence and identify regions of differential deformation relevant to infrastructure risk. The method enables horizontal deformation to be quantified from InSAR observations alone without requiring external geodetic velocity constraints.