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34 a Location of the Zuojiazhuang Well and the epicenter of the 2011 Tohoku earthquake. b Simplified lithological profile of the borehole. (F1 is the Huangzhuang-Gaoliying fault, F2 is the Shunyi-Qianmen-Liangxiang fault, F3 is the Nanyuan-Tongxian fault, F4 is the Xiandian fault, F5 is the Changping-Fengnan fault, and F6 is the Nankou-Sunhe fault) (from Zhang-Shi et al. 2019)
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Groundwater responses to Earth tides and barometric pressure have long been reported and increasingly used in hydrogeology to advance our understanding of groundwater systems. The response of groundwater to seismic waves has also been used in recent years to study the interaction between earthquakes and fluids in the crust. These methods have gaine...
Citations
... The confined pore pressure generated by earth tide strain is a mechanical phenomenon caused by the elastic deformation of the porous matrix (Wang & Manga, 2021). The barometric pressure response model investigates three one-dimensional flow problems, unlike the earth tide response which is a direct action on the matrix. ...
Aquifer pumping tests represent a standard method for estimating hydraulic characteristics, with practitioners often focusing on late period drawdown data because these are less affected by within‐ and near‐borehole effects (e.g., borehole‐storage and skin effects). Alternatively, groundwater responses to natural forcing (e.g., barometric pressure and earth tides) provide a passive method for estimating aquifer parameters at a low cost. However, to the best of our knowledge, no studies have compared parameters calculated from different periods within a pumping test with those from passive methods. Herein, we compare the aquifer transmissivity estimated using both active and passive methods in two wells located in the Beetaloo Region of Northern Australia. The active method estimates aquifer transmissivity during three periods (i.e., the early, middle, and late periods) of an aquifer pumping test, while the passive method employs groundwater responses to barometric‐pressure and earth‐tide fluctuations. We find that the range of best‐fit aquifer transmissivity is 1.18 × 10⁻⁵–1.79 × 10⁻⁵ m²/s and 1.73 × 10⁻⁵–2.14 × 10⁻⁵ m²/s for OW1 and OW2, respectively. The transmissivity estimated from the barometric pressure response method is the largest. The aquifer transmissivity using barometric pressure responses are consistent with early‐ and middle‐period estimates. This suggests that barometric pressure responses are more sensitive to within‐ and near‐borehole effects. The scales of the tidal response method are smaller than those of the pumping test method.
... Zhu and Wang (2020) simulated a multi-layered system to study the effect of leakage through an aquitard and concluded that simplifications in the analytical model lead to overly conservative estimates of vertical flux between layers. Wang and Manga (2021) provide a summary of these works. ...
... Here, we develop a novel numerical approach for simulating the groundwater response to Earth tides. This allows a more realistic physical representation compared to the limiting assumptions of the analytical solution presented in Section 2.2 and advances the previous study by Wang & Manga (2021). The aim is to investigate and establish robustness of the analytical solution when interpreting the groundwater response to Earth tides. ...
Harmonic Earth tide components in well water levels have been used to estimate hydraulic and geomechanical subsurface properties. However, the robustness of various methods based on analytical solutions has not been established. First, we review the theory and examine the latest analytical solution used to relate well water levels to Earth tides. Second, we develop and verify a novel numerical model coupling hydraulics and geomechanics to Earth tide strains. Third, we assess subsurface conditions over depth for a range of realistic properties. Fourth, we simulate the well water level response to Earth tide strains within a 2D poroelastic layered aquifer system confined by a 100 m thick aquitard. We find that the non‐linear inversion of analytical solutions to match two observations (amplitudes and phases) to multiple unknown parameters is sensible to the initial guess. We reveal that undrained, confined conditions are necessary for the analytical solution to be valid. This occurs for the dominant M2 frequency at depths >50 m and requires specific storage at constant strain of Sϵ ≥ 10⁻⁶ m⁻¹, hydraulic conductivity of the aquitard of kl ≤ 5 ⋅ 10⁻⁵ ms⁻¹ and aquifer of ka ≥ 10⁻⁴ ms⁻¹. We further illustrate that the analytical solution is valid in unconsolidated systems, whereas consolidated systems require additional consideration of the Biot modulus. Overall, a priori knowledge of the subsurface system supports interpretation of the groundwater response. Our results improve understanding of the effect of Earth tides on groundwater systems and its interpretation for subsurface properties.
