Application of advanced InSAR techniques to detect vertical and horizontal displacements

Jessica Morgan1, Simit Raval2, Bruce Macdonald1, Giacomo Falorni1, Jean Pascal Iannacone3

1 - TRE Canada Inc., Canada, 2 - ACSMP, 3 - University of Modena and Reggio Emilia, Italy

The monitoring of surface subsidence is an important aspect in many underground mines. There are various ground-based methods that can be used for deformation monitoring, including optical levelling, GPS, and tiltmeters. This study proposes the use of satellite-based InSAR for the monitoring of surface movement over the Metropolitan Mine, an underground coal mine located in the Southern Coalfields of New South Wales, Australia where ground subsidence has been documented. An advanced multi-image InSAR approach, characterised by a high density of measurement points and millimetre precision, is applied to illustrate how results provide an overview of surface displacement dynamics before, during and after active mining. Two stacks of ENVISAT radar imagery (87 total images) acquired between June 2006 and August 2010 were analysed with the SqueeSAR™ algorithm to reconstruct ground movement patterns during this period. Movements were assessed on a 35-day interval (the revisitation frequency of the ENVISAT satellite), and a time series of deformation was generated for every measurement point. The use of two image stacks acquired from different viewing geometries allowed both the vertical and east–west components of ground movement over this site to be determined. Results illustrate the surface-level impact of underground mining by quantifying the spatial extent and timing of surface movement. The precision of the InSAR data were briefly assessed by comparing results with ground-based GPS survey measurements. While the timing and direction of movements were similar, the comparison was limited by the lack of both spatial and temporal overlap of the data sets. The use of a radar satellite with a higher temporal frequency is recommended for future monitoring of this site.

 

Measured surface displacement rates for the decomposed vertical (left panel) and east-west horizontal movement (righr panel), expressed in millimetres per year (Morgan et al. 2013)