An Alternative Approach for Constraining 3D‐Displacements With InSAR, Applied to a Fault‐Bounded Groundwater Entrainment Field in California

Abstract

Interferometric Synthetic Aperture Radar (InSAR) observations constrain displacement of the Earth's surface toward or away from the satellite, and are inherently a one-dimensional observation defined by the projection of the true, 3-dimensional (3-D) ground displacement field onto the orientation of the line-of-sight (LOS) vector between the satellite and the ground (e.g., Bürgmann et al., 2000). However, interpretations of the deformation within a given region usually benefit from constraints on the full 3-D displacement field (e.g., Fialko et al., 2001;Funning et al., 2005;Wright et al., 2004) or require well-characterized physical models of the processes driving the deformation (e.g., fault source geometry, aquifer characteristics, crustal rigidity). These models are not always available or well understood and the Earth is far more complex in reality than its representation in models (e.g., Caricchi et al., 2014;Chester & Chester, 2000;Hearn & Bürgmann, 2005). To address this limitation, researchers have combined measurements from multiple observation geometries (particularly from ascending and descending satellite paths) as well as other products derived from the Synthetic Aperture Radar (SAR) imagery (described below) to infer the 3-D displacement field and its variations over time (e.g.

Enhanced Kinematic Inversion of 3‐D Displacements, Geometry, and Hydraulic Properties of a North‐South Slow‐Moving Landslide in Three Gorges Reservoir

“…The displacement of the neighboring points on the landslide can be linked by some geophysical relationships. An example of this is the elastically coupled solution in which the connection between horizontal subsurface forces and displacement is built to improve the performance of deriving groundwater‐induced 3‐D deformations (Murray et al., 2021). The strain tensor is another connection that describes the strain constraints of the 3‐D deformations among the neighboring points and had been implemented in the study of landslides (Handwerger et al., 2019).…”

“…Even if more than three independent InSAR measurements are available, for the north‐south slope, the ill‐posed problem could reduce the reliability of the derived 3‐D movements (J. Hu, Li, et al., 2014). Deriving 3‐D deformations constrained by some models is the optimal solution for specific geophysical events, which can significantly reduce the requirement of datasets and has been implemented in many fields, associated with volcanoes (J. Hu et al., 2017), glaciers (Samsonov, 2019), and subsidence (Murray et al., 2021; Yang et al., 2017). The surface‐parallel flow (SPF) constraint, as the primary geo‐prior‐based method for deriving landslide movements, estimates the 3‐D movements of slow‐moving landslides by establishing the relationship between vertical and horizontal deformations based on the gradient of aspect and slope (Joughin et al., 1998; Samsonov, 2019).…”

Improving the Understanding of Landslide Development in Alpine Forest Regions Using the InSAR Technique: A Case Study in Xiaojin County China

“…However, considering the spatial variation in the geological conditions and the failure mechanism of landslides, the DRTs may vary among different regions and cannot be defined by a fixed rule. Nevertheless, the deformation of the landslide body is controlled by the failure mechanism and is continuously distributed in space but cut off at the landslide boundary [42]. This suggests that, from the spatial statistic viewpoint, the deformation would cluster in the landslide body.…”

“…SAR satellites have various advantages, such as being able to penetrate vegetation, continuously observe the earth surface with all-day and all-weather capability, and collect high-resolution SAR images with a short time interval [34]. With continuous SAR images, Interferometric SAR (InSAR) techniques, including Differential InSAR (D-InSAR) [35,36], Permanent Scatterer (PS) InSAR [37,38], and Small Baselines Subset (SBAS) InSAR [39,40], can be applied to analyze ground deformation and identify potential landslides with high precision, especially in alpine forest regions [41,42]. For example, Bianchini et al [43] identified 1012 active landslides and 64 new potential landslides within an area of 4470 km 2 in the Calabria region, south Italy, using ENVISAT data.…”

Space Geodetic Views on the 2021 Central Greece Earthquake Sequence: 2D Deformation Maps Decomposed From Multi-Track and Multi-Temporal Sentinel-1 InSAR Data

“…When earthquakes do not rupture the surface, it is hard to identify fault trace and even the dipping direction from a " visually deceptive" 1D displacement because reported cases revealed that different mechanisms can cause the same 1D LOS displacements [7,8]. The issues mentioned above can be potentially solved using multidimensional deformations [9][10][11][12][13]. Integrating ascending and descending track InSAR measurements with different viewing geometries can generate 2D (East-West and Up-Down) deformations to avoid visual fraud in parameters determination [14].…”