GEOPHYSICAL INVESTIGATION OF FLOOD-INDUCED SINKHOLE COLLAPSES IN SOUTHEASTERN NEW MEXICO

Following flooding in September 2013, several areas in northern Eddy County, New Mexico were damaged by multiple sinkhole collapses. We conducted electrical resistivity (ER) surveys for subsurface cavities parallel to roads within and near the community of Lakewood, NM to guide road repairs. ER surveys attained a maximum exploration depth of 55 to 62 m. Subsurface stratigraphy, including clay-rich floodplain sediments, and mudstone and gypsum of the underlying Seven Rivers Formation, can be identified by vertical and lateral variations in electrical resistivity. The irregular bedrock surface of the Seven Rivers Formation reflects paleotopography developed on that surface prior to its burial by floodplain sediment. Some of the negative paleotopographic features are probably filled sinkholes, which may be associated with shallower karstic features not imaged on the profiles.