Provided herein are methods for identifying a region of a geologic area comprising a fault or other feature associated with a pressure loss. Such methods can comprise (1) subjecting rock samples from separated sites in an area to condition(s) that can cause the release of carbon dioxide (CO2), one or more volatile carbon dioxide-related, or both, if present, while not causing the release of a significant amount of CO2 or the one or more CO2-related compounds associated with the crystalline structure of the material, (2) measuring the amount of CO2, the one or more related compounds, or both, and (3) identifying regions in the geologic area associated with a relatively low CO2, related compounds, or both, or similar or alternative methods involving the analysis of such compositions associated with materials provided here.