| Interferometric Synthetic Aperture Radar, or InSAR, has proven to be an invaluable tool for ground motion studies in the geosciences. It was not until recently that InSAR has been used extensively for the delineation of aquifer system response to heavy groundwater pumping. A number of studies have demonstrated the vastly improved spatial resolution afforded by InSAR relative to traditional surveying techniques in detecting groundwater-related subsidence.;Ground subsidence related to mine dewatering is a common occurrence due to the large volumes of water that are pumped in order to lower the local groundwater table to facilitate open pit and underground mining operations. Several mines located along the Carlin Trend of Central Nevada have produced InSAR identified subsidence signals of greater aerial extent and magnitude than most municipal groundwater signals. The dewatering signal at Betze-Post shows a minimum of 45.8 cm of cumulative subsidence between June 1, 1992 and September 21, 2000. Our study has created many (>50) interferograms, allowing a better understanding of how the subsidence signal evolved in response to varied pumping rates from dewatering wells. The deformation signal correlates well with the observed groundwater drawdown characteristics. However, since the spatial resolution of the InSAR is much better than that of the monitoring well locations, the complexity of the signal is better delineated. The maximum aerial extent of the subsidence feature extends as far as 20 km away from the location of the extraction wells used for dewatering.;Of greatest interest is the fact that this subsidence signal exists mostly in areas of very shallow or exposed bedrock. Groundwater related bedrock subsidence of this scale is rarely, if ever, observed, and therefore, poorly understood. This study utilizes InSAR results to devise a simple, one dimensional bedrock subsidence model that utilizes easily obtained rock mass characteristics. |
