This presentation will focus on a recent case study from southwestern Pennsylvania relating to the inexplicable submergence of a surface stream. Using the method described above, investigators were able to map the stream’s subsurface flow through a fractured terrain.

Because different subsurface materials (granite, shale, limestone, etc.) have different levels of electrical conductivity, when the injected current passes from an area dominated by one material to an area dominated by another, the change in conductivity will effect a change in the emitted magnetic field—thus sending vital geological information to the investigators at the surface.  In the case study considered here, this method facilitated a clear definition of the location and orientation of a boundary between a sandstone region and a shale region running perpendicular to the streambed.  It also revealed that the primary groundwater channel diverged from the stream path at the stream’s intersection with this boundary and indicated the recent development of a fault line along the shale-sandstone boundary.

In this case and others, this method demonstrated the ability to generate vital information about a fractured site. This paper will discuss both the theoretical science behind this method and the lessons learned from its recent applications.