Several evidential layers calculated from a compilation of gravity data from the national-scale gravity anomaly map of the conterminous United States (Phillips and others, 1993), Alaska (Saltus and others, 2006) and Canada (Geological Survey of Canada, 2017) are presented here. This directory includes GeoTIFF grids of Bouguer gravity, the horizontal gradient magnitude of the Bouguer gravity, the Bouguer gravity upward continued 30 km, and the horizontal gradient magnitude of the upward continued gravity, The directory also includes shapefiles of locations that trace the maxima of the horizontal gradient magnitude of the gravity and of the maxima of the horizontal gradient magnitude of the upward continued gravity. Otherwise known as “worms”, the points tracking the maxima mark the edges of shallow density sources (in the case of the Bouguer gravity) and deeper density sources (calculated from the upward continued gravity). The shapefile of worms also includes attribute fields related to the steepness of the gradient and to the trend or strike of the gradient. The reader is encouraged to read the metadata provided in the zip file that is specific to each data layer for details related to the calculation and derivation of each gravity grid and derivative products.

References Geological Survey of Canada, 2017, Canada-gravity data compilation: Natural Resources Canada, https://open.canada.ca/data/en/dataset/5a4e46fe-3e52-57ce-9335-832b5e79fecc.

Phillips, J.D., Duval, J.S., and Ambroziak, R.A., 1993, National geophysical data grids; gamma-ray, gravity, magnetic, and topographic data for the conterminous United States: U.S. Geological Survey Data Series 9, https://doi.org/10.3133/ds9.

Saltus, R.W., Brown, P.J. II, Morin, R.L., and Hill, P.L., 2008, 2006 compilation of Alaska gravity data and historical reports: U.S. Geological Survey Data Series 264, https://doi.org/10.3133/ds264.