How Groundwater Level Fluctuations and Geotechnical Properties Lead to Asymmetric Subsidence: A PSInSAR Analysis of Land Deformation over a Transit Corridor in the Los Angeles Metropolitan Area

Abstract

Los Angeles has experienced ground deformations during the past decades. These ground displacements can be destructive for infrastructure and can reduce the land capacity for groundwater storage. Therefore, this paper seeks to evaluate the existing ground displacement patterns along a new metro tunnel in Los Angeles, known as the Sepulveda Transit Corridor. The goal is to find the most crucial areas suffering from subsidence or uplift and to enhance the previous reports in this metropolitan area. For this purpose, we applied a Persistent Scatterer Interferometric Synthetic Aperture Radar using 29 Sentinel-1A acquisitions from June 2017 to May 2018 to estimate the deformation rate. The assessment procedure demonstrated a high rate of subsidence in the Inglewood field that is near the study area of the Sepulveda Transit Corridor with a maximum deformation rate of 30 mm/yr. Finally, data derived from in situ instruments as groundwater level variations, GPS observations, and soil properties were collected and analyzed to interpret the results. Investigation of geotechnical boreholes indicates layers of fine-grained soils in some parts of the area and this observation confirms the necessity of more detailed geotechnical investigations for future constructions in the region. Results of investigating line-of-sight displacement rates showed asymmetric subsidence along the corridor and hence we proposed a new framework to evaluate the asymmetric subsidence index that can help the designers and decision makers of the project to consider solutions to control the current subsidence.

Evaluation of deformations in the urban area of Olsztyn using Sentinel-1 SAR interferometry

“…However, in the building area, most average vertical motion rates range from -0.5 to 0.5 mm/yr. Khorrami et al (2019) in their work used 29 Sentinel-1A acquisitions from June 2017 to May 2018 to estimate the deformation rate in Los Angeles between -30 to 10 mm/yr. Vertical movements of the earth's crust occurring in Poland have been studied mainly based on leveling data, which in some works was analyzed together with data from mareograph so far.…”

“…Interferometric SAR can detect surface movements with an accuracy of a few millimeters per year and can provide an accurate tool for monitoring of land subsidence, structural damage and underground construction to improve safety and reduce economic loss (ESA Standard Document, 2013). Research that was conducted in various urban areas: Berlin, Leipzig (Haghighi and Motagh, 2017), Rome (Delgado Blasco et al, 2019), London (Bischoff et al, 2019), Paris (Koudogbo et al, 2019) and Los Angeles (Khorrami et al, 2019) have demonstrated the capability and great potential of Sentinel-1A/B (S-1) TOPS, TerraSAR-X and method PSI for monitoring slow deformation, including ground, single buildings and infrastructures. Using the StaMPS algorithm in Berlin, Haghighi and Motagh (2017), determined that from during October 2014 to January 2017 the deformation in the south-eastern part of Berlin was from -4 to 1 mm/yr.…”

Spatial Analysis of Land Subsidence in the San Luis Potosi Valley Induced by Aquifer Overexploitation Using the Coherent Pixels Technique (CPT) and Sentinel-1 InSAR Observation

“…Currently, there are several methods to measure ground deformations, from the most classical ones that involve the calculation of the variations of pore pressures and topographic variations on surfaces, to the most modern techniques including Global Navigation Satellite System (GNSS) and remote sensing methods [31]. Differential Interferometric Synthetic Aperture Radar (DInSAR) is a remote sensing technology that can provide high resolution, day and night, weather independent, wide-coverage, and high accuracy measurements of the earth's surface changes [32]. Thus, this technique can detect and monitor regional-scale surface subsidence at low cost with centimeter to millimeter accuracy [9,[32][33][34][35].…”

“…Differential Interferometric Synthetic Aperture Radar (DInSAR) is a remote sensing technology that can provide high resolution, day and night, weather independent, wide-coverage, and high accuracy measurements of the earth's surface changes [32]. Thus, this technique can detect and monitor regional-scale surface subsidence at low cost with centimeter to millimeter accuracy [9,[32][33][34][35]. DInSAR has been used to study settlements as a consequence of groundwater withdrawal around the world, especially in places where the population mostly depends on groundwater reserves, and as a consequence the exploitation of the available aquifers has taken place.…”

Editorial for the Special Issue “Urban Deformation Monitoring using Persistent Scatterer Interferometry and SAR Tomography”

“…The papers related to PSI describe methodological and application-oriented research work. In reference [8], the authors assess the deformations associated with the construction of a new metro tunnel. In reference [9], PSI results are used as a key input for geological and geomorphological analyses in urban areas.…”