Abstract
Abstract. Fast ground subsidence in southern Saskatchewan (Canada) between the city of Saskatoon and Rice Lake was observed with the RADARSAT-2 interferometric synthetic aperture radar (InSAR) during 2008–2011. We collected 23 ascending Multi-Look Fine 3 Far (MF3F) and 15 descending Standard 3 (S3) RADARSAT-2 images and performed time-series analysis utilizing Small Baseline Subset (SBAS) and Multidimensional SBAS (MSBAS) methodologies. We observed two well-defined circular regions located a few kilometers apart and subsiding with the nearly constant rate of about 10 cm yr-1. MSBAS decomposition revealed the presence of both vertical and horizontal ground displacements. For further analysis we selected two highly coherent interferograms spanning from November to December 2009 until April 2010 thanks to particularly favorable ground conditions that displayed superior coherence. We performed modeling and inversion assuming spherical and sill source models in order to determine the source location, depth and strength. The sill source model produced the smallest residual of 0.7 cm yr-1 applied to ascending interferograms and 0.9 cm yr-1 applied to descending interferograms. A residual of 1.0 cm yr-1 was achieved with the sill model when both ascending and descending interferograms were used. This model suggested sources located at 1.3 and 1.2 km depth with radius of 1.0 and 1.3 km for eastern and western areas, respectively. The spherical model suggested slightly shallower sources located at 0.9 and 0.8 km. We could not precisely identify the cause of this deformation, but the observed subsidence rate and source depth suggest mining-related origin. Topographic changes produced by this subsidence rate over a long time may produce shallow groundwater redistribution and flooding of agricultural lands.
Highlights
Ground subsidence, a downward motion of the earth surface in relation to its position at an earlier time, can be produced by natural and anthropogenic phenomena
Noise is simulated based on the estimated parameters on the full-resolution interferogram far from the deformation area, with σ = 0.50871cm yr−1, a = 0.41988 km−1, and b = 4.8e−8 km−1
Noise is simulated based on the estimated parameters on the full-resolution interferogram far from the deformation area, with σ = 0.60259cm yr−1, a = 0.024478km−1, and b = 0.06812km−1
Summary
A downward motion of the earth surface in relation to its position at an earlier time, can be produced by natural and anthropogenic phenomena. Among the natural causes are the earthquakes and more general fault motion (Beavan et al, 2010, 2011; Wen et al, 2013), volcanic thermal and pressurized sources (Samsonov and d’Oreye, 2012), karst processes (Klimchouk, 2005), consolidation of sediments (Mazzotti et al, 2009) and permafrost thawing (Short et al, 2011; Chen et al, 2012). Subsidence produced by earthquakes, mining collapse and sinkholes generated by karst processes is usually. Samsonov et al.: Modeling of ground deformation in Saskatchewan, Canada spatially and temporally localized, with no detectable preevent motion; other processes usually occur over an extended period of time and can be detected by ground-based or spaceborne measurements. The process opposite to ground subsidence, is observed but with a rare frequency and usually associated with natural volcanic activities (Biggs et al, 2010; Amelung et al, 2000; Fialko and Pearse, 2012) or anthropogenic liquid, gas or steam injection (Teatini et al, 2011; Samsonov et al, 2013a)
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