Understanding Temporal Variations in Fault-Controlled Fluid Flow
The role of faults in subsurface transport of heat and fluids has implications in many socially and economically important areas, such as petroleum and geothermal reservoir engineering, CO2 sequestration, nuclear waste disposal, and ore deposition. Although a large body of work suggests that thermal, hydrochemical, and pressure distributions in faults may be driven by seismic activity and thermal-convective instability, establishing definite relationships between these factors has proven difficult, largely due to inability to observe subsurface processes directly. In this study, we will test the hypothesis that temperature and geochemical variability observed in fault-controlled springs are the result of a combination of seismic activity, thermal-convective instability, and environmental forcing (i.e., diurnal and seasonal atmospheric temperature changes). To test this hypothesis, we are gathering temperature data at 15 minute intervals from 18 geothermal springs that are in direct hydraulic contact with the Borax Lake fault, an active normal fault in the Alvord Basin of southeast Oregon. This temperature data will be analyzed using discrete Fourier analysis to establish the influence of periodic/quasi-periodic (i.e., environmental forcing) and seismic driving forces on spring temperatures. Residual variability in the time-series data not related to environmental and seismic drivers will be examined for evidence of non-linear deterministic behavior (i.e., "chaos") that may arise from unstable convection or complex variations in the stress-field of the fault. Apart from its scientific/technical merits, this research will further graduate education in the geosciences, and enhance educational opportunities for undergraduates from non-PhD granting institutions by providing internships and/or summer research projects.