Post-processing of InSAR persistent scatterer time-series to investigate deformational processes induced by subsurface excavation

Abstract

Over the past 30 years, space-based geodetic measurements have become mainstream by applying Interferometric Synthetic Aperture Radar (InSAR). Standard InSAR time-series analyses can extract phase-based measurements of surface deformation with sub-centimeter, in some cases even sub-millimeter, accuracy. However, the standard analyses can only make measurements within a single viewing geometry, i.e., the Line Of Sight (LOS) of the sensor. Additionally, these analyses can be impacted by noise when applied to vegetated areas or tropical areas subject to turbulent atmospheric changes. The research projects described in this dissertation are designed to take advantage of a new generation of temporally dense, multi-angle InSAR measurements by developing novel post-processing algorithms to reduce remaining data noise and resolve tunneling-induced subsidence in three dimensions. Findings from these projects are organized into the following three chapters: (1) Application of a novel 4-D filtering algorithm, designed to remove phase noise from InSAR data acquired in highly vegetated, tropical locations, to a widespread subsidence event in the highlands of Sri Lanka. (2) Adaptation of previously published algorithms that resolve satellite InSAR measurements into vertical and horizontal motion through a case study of subsidence events in Seattle, Washington, USA to reveal heterogeneous rebound and additionally delayed subsidence. (3) A novel modification to the minimum-acceleration algorithm allowing it to combine multiplatform SAR data, especially to ingest airborne InSAR data, and produce true 3D (Vertical, East-West, and North-South) deformation time series of a small magnitude, spatially acute tunneling-induced subsidence event in Los Angeles, California, USA. Algorithm results are shown to produce accurate and precise data, and results provide new insights into deformation processes induced by tunneling activities.