ELECTRICAL IMAGING OF A SUBSIDING ABANDONED COAL MINE IN SUMMIT COUNTY, OHIO

Ground penetrating radar and multi-channel electrical resistivity were found to be effective methods for imaging a previously undocumented, subsiding coalmine in northeast Ohio. Subsidence of the mine resulted in a surface void that was confirmed to be associated with an abandoned mine by coring by the Ohio Department of Natural Resources. Ground penetrating radar data were collected in a 1m by 1m grid that covered a 20m by 80m area. This was done in order to determine the spatial extent of the mine and to image subsurface structures. Electrical resistivity data were also collected in a 1m by 1m grid over the same 20m by 80m area for comparison of the two methods. The radar results show a strong reflection located at 10m depth throughout the entire survey area, along with several localized disturbances in the nearly horizontal layers of the subsurface. The resistivity data show a highly resistive zone at approximately 10 meters depth in all of the profiles. This zone of high resistivity correlates well with the strong linear reflection in the radar data. These features are characteristic of a void in the subsurface, and may represent the abandoned mine. Such abandoned coalmines may subside and pose a significant threat to homeowners in Ohio and elsewhere. More study is needed to document the geophysical characteristics of these mines so they can be located to mitigate potential losses associated with their structural failure.