Analysis of the geometry of surface deformations caused by induced tremors in the area of underground copper mining

Abstract

Induced seismicity by human operations such as mining is usually unpredictable due to the sudden and unexpected character of this phenomenon. The effects of seismic events on the surface, i.e. ground deformation had been difficult to measure with traditional geodetic methods, which are based on discrete point observations and are carried out at temporal intervals and in fixed locations (e.g. levelling lines). Development of radar remote sensing (InSAR) techniques and proliferation of open satellite radar data such as Sentinel-1 mission provides means that can now be successfully applied to investigate areas and ground movements affected by seismicity induced by mining. In this paper four induced seismic events with magnitudes from 4.5 to 4.8 that occurred between 16 December 2016 and 15 September 2018 in the Rudna underground copper mine area in SW Poland have been investigated with differential satellite radar interferometry (DInSAR). Based on the results of processing of 37 pairs of Sentinel-1 data captured before and after each of these events, deformation areas have been spatially localised and vertical displacement and extent of deformation have been calculated. The mean maximum vertical displacements range from −70-mm for the 4.5 magnitude tremor to −94-mm for the 4.8 magnitude event. Whereas, mean extent ranges from 1.5-km to 1.9-km in the W-E direction and from 1.8-km to 2.1-km in the N-S direction. A linear relation between magnitude of induced tremor and increase in vertical displacement and extent of the ground deformation has been established. Moreover, the results of this study indicate that InSAR is adequately accurate technique to analyse ground displacements caused by mining induced tremors and provides continuous field data on the geometry of the resulting deformation areas.