The application of satellite radar interferometry to the study of land subsidence over developed aquifer systems

This dissertation investigates the application of interferometric synthetic aperture radar (InSAR) to measuring and interpreting surface displacements over developed aquifer systems. These widely observed displacements result from elastic and inelastic deformation of water-bearing material at depth due to pore-fluid pressure changes. InSAR satellite data can map surface displacements over extensive areas at millimeter precision and high spatial detail. This work uses InSAR to investigate time-dependent deformation processes in aquifer systems. InSAR-derived displacements have not previously been employed to estimate heterogeneous aquifer system parameters. Where applicable, InSAR provides a powerful tool for characterizing aquifer systems, which often are an important resource to local communities.; I have used InSAR to map the recent time-varying surface displacement fields over the Las Vegas Valley, Nevada and Antelope Valley, California aquifer systems, obtaining detailed and spatially complete characterizations of the heterogeneous displacement fields. The structure of the displacement fields often reflects known or previously unknown subsurface structure such as faults or changing sediment thicknesses, emphasizing the value of InSAR in delineating subsurface units. A comparison of displacements measured with different viewing geometries indicated primarily vertical surface displacements in Antelope Valley. This has been a widely used, albeit hitherto generally untested assumption in basin-scale studies of land subsidence.; The observed displacement fields reflect effects of both seasonal fluctuations and long-term stress trends in the aquifer system. Combining InSAR observations with other information on these stress variations I estimated heterogeneous storage parameters for the aquifer systems. In Las Vegas Valley, the estimated aquifer system elastic skeletal storage coefficients range from 4.2 · 10−4 to 3.4 · 10−3. In Antelope Valley, since the drainage of thick low-conductivity units is delayed with respect to aquifer drawdowns, subsidence continues for decades after the hydraulic head declines have ceased. Here I estimated inelastic skeletal storage coefficients up to 0.09 and compaction time constants for interbed compaction ranging from 3 to 285 years in a three-dimensional groundwater flow and subsidence (MODFLOW) model.; Numerical simulations show that the accuracy and frequency of InSAR observations are sufficient to constrain storage parameter estimations. However, unreliable drawdown estimates in regional aquifer systems severely limit these analyses.