From the site: "A reference map of systematic coal-fracture trends, fracture domain, and Mississippian shale, sandstone, and limestone fractures in the Allegheny Plateau published by the WV Geological and Economic Survey in 1980.

In May/June 2007, two hardcopy map sheets of the 1980 Fracture Trends in the Allegheny Plateau of West Virginia were scanned at 300 dpi 8-bit color by the WV GIS Technical Center. The scanned TIFs were converted to index color mode, and resampled to 150 dpi. The map sections were then mosaicked together and georeferenced to a 15-minute Longitude/Latitude grid."