Understanding Temporal Variations in Fault-Controlled Fluid Flow

Fairley 0511061断层在地下热量和流体传输中的作用在许多社会和经济重要领域都有影响，如石油和地热油藏工程、二氧化碳封存、核废料处理和矿石沉积。尽管大量工作表明断层中的热、水化学和压力分布可能是由地震活动和热对流不稳定性驱动的，但事实证明，很难在这些因素之间建立明确的关系，这主要是因为无法直接观察地下过程。在这项研究中，我们将检验这样一种假设，即在断层控制的泉水中观察到的温度和地球化学变异性是地震活动、热对流不稳定和环境强迫(即大气温度的昼夜和季节变化)共同作用的结果。为了验证这一假设，我们每隔15分钟收集18个地热泉水的温度数据，这些温泉与俄勒冈州东南部阿尔沃德盆地的一条活动正断层Borax Lake断层有直接的水力接触。这些温度数据将使用离散傅立叶分析进行分析，以确定周期/准周期(即环境强迫)和地震驱动力对春季温度的影响。将检查与环境和地震驱动因素无关的时间序列数据中的残差变异性，以寻找可能由不稳定对流或断层应力场的复杂变化引起的非线性确定性行为(即“混沌”)的证据。除了科学/技术方面的优点外，这项研究还将通过提供实习和/或暑期研究项目，进一步促进地球科学研究生教育，并增加非博士授予机构的本科生接受教育的机会。

FAIRLEY 0511061The 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.