Detecting Groundwater Change Within the Jackson Purchase Region, Kentucky, with the CLIMBS Seismic Array: Project Design, Instrument Evaluation, and First Observations

Abstract The aquifer system of the northern Mississippi Embayment (NME) supports the water needs of agriculture, industry, and an increasing population in a large region in the central United States. Groundwater usage in Kentucky’s part of the NME, the Jackson Purchase Region (JPR), is experiencing increasing demand, motivating improved monitoring of this currently sparsely monitored resource. Seismic interferometry has successfully monitored groundwater change in areas where long-term recordings of ambient seismic noise are available. However, the JPR, which hosts multiple aquifers from the surface to depths greater than 500 m, is insufficiently instrumented for such monitoring. Thus, we are conducting an approximately four-year interferometric investigation of the JPR using a deployment of 35 densely arranged (∼10 km spacing) seismometers. The array was installed in the winter of 2025–2026, and data collection is ongoing. Here, we present an overview of the project, including the hydrogeological targets, ongoing groundwater and meteorological monitoring in the JPR, and the CLIMBS seismic array. We also present results of our evaluations of cost-effective instruments, as well as initial cross-correlation functions (CCFs) and short-term (two months) velocity-change (dv/v) estimations determined from those CCFs. Our preliminary CCFs demonstrate stable seasonal variations in the coda waves. The preliminary dv/v suggest groundwater level influences seismic velocity variation in the JPR’s unconfined aquifer. In contrast, the relationship between dv/v and groundwater elevation in the confined aquifers is unclear. These observations suggest complex dv/v responses in the project area, and we anticipate identifying the main influencers of dv/v with longer-term array observations. We identified challenges in our initial analyses yet anticipate addressing them and yielding the first high-resolution, regional-scale assessment of groundwater fluctuations within the JPR.