Abstract
In this paper, we investigate land motion and groundwater level change phenomena using differential interferometric synthetic aperture radar (DInSAR) over the Northumberland and Durham coalfield in the United Kingdom. The study re-visits earlier research that applied a persistent scatterers interferometry (PSI) technique to ERS (European Remote Sensing) and ENVISAT (Environmental Satellite) data. Here, the Intermittent Small Baseline Subset (ISBAS) DInSAR technique is applied to ERS, ENVISAT and Sentinel-1 SAR datasets covering the late 1990s, the 2000s and the mid-2010s, respectively, to increase spatial coverage, aid the geological interpretation and consider the latest Sentinel-1 data. The ERS data identify surface depressions in proximity to former collieries, while all three data sets ascertain broad areas are experiencing regional scale uplift, often occurring in previously mined areas. Uplift is attributed to increases in pore pressure in the overburden following the cessation of groundwater pumping after mine closure. Rising groundwater levels are found to correlate to ground motion measurements at selected monitoring sites, most notably in the surrounding area of Ashington. The area is divided by an impermeable EW fault; to the south, surface heave was identified as groundwater levels rose in the 1990s, whereas to the north, this phenomenon occurred two decades later in the 2010s. The data emphasize the complexity of the post-mining surface and subsurface environment and highlight the benefit that InSAR, utilizing the ISBAS technique, can provide in its characterization.
Highlights
High precision satellite radar interferometry is an effective and well established technique for monitoring earth surface motion [1]
Temporal gaps are common due to large deformation gradients often associated with mining subsidence [8,9] and decorrelation, the loss of coherence, which is common over coal mining areas [10]
The results demonstrated that the Intermittent Small Baseline Subset (ISBAS) technique can be used with confidence over locations where traditional ground-based survey measurements are not available
Summary
High precision satellite radar interferometry is an effective and well established technique for monitoring earth surface motion [1]. It is a cost-effective method capable of surveying extensive areas to within millimetre precision regardless of weather and illumination conditions [2]. Differential interferometric synthetic aperture radar (DInSAR) utilizes stacks of high resolution synthetic aperture radar (SAR) data acquired over time from spaceborne platforms. Temporal gaps are common due to large deformation gradients often associated with mining subsidence [8,9] and decorrelation, the loss of coherence, which is common over coal mining areas [10]
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