FINAL REPORT: Potential Field Surveys, Analyses, and Interpretation for Cornell’s Earth Source Heat Project
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This work was contracted to look for geological structures that might be proximal to the proposed drilling sites for Cornell University’s Earth Source Heat (ESH) project. I used geophysical gravity and magnetic (collectively: potential field or PF) surveys as the underlying data from which I primarily formed my interpretations. PF surveys offer a relatively low-cost means of identifying underground geological structures in an area of interest. While they certainly can not attain the resolution available from seismic reflection surveys, their low-cost affords a method of covering a much larger map area of interest than would be economical via 2D or 3D reflection seismic surveys. Here, I report on results and interpretations derived from two independent PF surveys. First, during July 2018 – with the help of field assistants – a gravity survey was performed in the region using a rented Scintrex CG5 gravity meter. Second, a commercial aeromagnetic survey – flown on speculation during exploration activity for the Trenton-Black River gas play in 1999 – was purchased for Tompkins county from geophysical service company EDCON-PRJ. Both of these data sets were analyzed using a Poisson wavelet multi-scale edge analysis of potential fields, informally known as the ‘worm’ technique. This technique uses gravity and magnetic fields to detect lateral contrasts (“edges”) in mass density or magnetization strength, respectively. There are several geological structures found by this work. Some of them are previously known or have been inferred, while several of them are new. The gravity survey found one strong and apparently deep structure of interest to the south of the Cornell campus. The structure strikes roughly E-W and dips about 60° to the north. The analysis of the aeromagnetic data shows another strong and deep feature in roughly the same area, with a similar strike but the opposite sense of dip. The limited precision inherent in these measurements, along with multiple possible explanations for the inferred lateral contrasts in bedrock properties, do not allow us to reach specific conclusions regarding the nature of the geologic structures present. However, these data complement the seismic reflection data to further illuminate the deep bedrock structure near the Cornell campus, and will provide context for planned cutting and core sample analysis during installation of the initial test well.
Earth Source Heat; Geothermal; Potential Fields; Gravity; Magnetics