Abstract Earth tides, the response of the earth’s crust to global gravity forces, have generally been detected as changes in tilt and strain and as changes in groundwater potential. Changes in volume strain due to earth tides are believed to be responsible for some types of fluid flow in porous materials and rock fractures of the subsurface environment. The focus of the presented work is on the study of micro-temperature variations associated with fluid flow, in observation wells drilled at the campus of the University of Gottingen, Germany. According to the results obtained by long-term and high precision temperature measurements in the subsurface indicate transient heat flow components of different origins. The diurnal and seasonal changes as well as long-term variations in temperature at ground surface propagate into the subsurface. Temperature perturbations by fluid flow, induced by the deformation of the earth’s crust following tectonic and earth tidal stress changes, are found to be superimposed on thermal effects of heat flow of the earth’s interior. Periodic micro-temperature variations with peak to peak amplitudes of ca. 2 mK were identified in the recorded data by time series analysis. At larger depths (>30 m) the conductive penetration of the annual surface temperature variation does not exceed 1 mK, but fluid flow mainly in fractured rock aquifers have been found to be capable of contributing to transient heat flow components with temperature effects of magnitudes larger than 1 mK. Such temperature variations have been attributed to changes in volume strain induced by earth tides. Earth tidal signals can be identified in the frequency spectra of long-term thermal time series, recorded in observation wells.

中文翻译：

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地下微温测量揭示的地球潮汐

摘要 地球潮汐是地壳对全球重力的响应，通常被检测为倾斜和应变的变化以及地下水势的变化。地球潮汐引起的体积应变变化被认为是多孔材料中某些类型的流体流动和地下环境的岩石破裂的原因。所介绍工作的重点是在德国哥廷根大学校园钻探的观测井中研究与流体流动相关的微观温度变化。根据地下长期高精度温度测量结果表明不同来源的瞬态热流分量。地表的昼夜和季节变化以及温度的长期变化会传播到地下。流体流动引起的温度扰动由地壳随构造和地球潮汐应力变化引起的变形引起，被发现叠加在地球内部热流的热效应上。周期性微温度变化，峰峰值幅度约为 通过时间序列分析在记录的数据中鉴定了 2 mK。在较大的深度（> 30 m），年地表温度变化的传导穿透不超过 1 mK，但已发现主要在裂隙岩石含水层中的流体流动能够促成瞬态热流分量，其温度效应的量级更大大于 1 mK。这种温度变化归因于地球潮汐引起的体积应变的变化。