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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Seismicity induced by seasonal groundwater recharge at Mt. Hood, Oregon
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Seismicity induced by seasonal groundwater recharge at Mt. Hood, Oregon

机译：山顶季节性地下水补给引起的地震作用。俄勒冈胡德

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Groundwater recharge at Mt. Hood, Oregon, is dominated by spring snow melt which provides a natural largeamplitude and narrow-width pore-fluid pressure signal. Time delays between this seasonal groundwater recharge and seismicity triggered by groundwater recharge can thus be used to estimate large-scale hydraulic diffusivities and the state of stress in the crust. We approximate seasonal variations in groundwater recharge with discharge in runoff-dominated streams at high elevations. We interpolate the time series of number of earthquakes, N, seismic moment, M_o, and stream discharge, Q, and determine cross-correlation coefficients at equivalent frequency bands between Q and both N and M_o. We find statistically significant correlation coefficients at a mean time lag of about 151 days. This time lag and a mean earthquake depth of about 4.5 km are used in the solution to the pressure diffusion equation, under periodic (1 year) boundary conditions, to estimate a hydraulic diffusivity of k ≈ 10~(-1) m~2/s, a hydraulic conductivity of about k_h ≈ 10~(-7) m/s, and a permeability of about k ≈ 10~(-15) m~2. Periodic boundary conditions also allow us to determine a critical pore-fluid pressure fraction, P'/P_0 ≈ 0.1, of the applied near-surface pore-fluid pressure perturbation, P_0 ≈ 0.1 MPa, that has to be reached at the mean earthquake depth to cause hydroseismicity. The low magnitude of P' ≈ 0.01 MPa is consistent with other studies that propose 0.01 ≤ P' ≤ 0.1 MPa and suggests that the state of stress in the crust near Mt. Hood could be near critical for failure. Therefore, we conclude that, while earthquakes occur throughout the year at Mt. Hood, elevated seismicity levels along pre-existing faults south of Mt. Hood during summer months are hydrologically induced by a reduction in effective stress.
机译：富士山的地下水补给俄勒冈州的胡德市以春季融雪为主，后者提供了自然的大振幅和窄宽度的孔隙流体压力信号。因此，该季节性地下水补给与由地下水补给触发的地震活动之间的时间延迟可以用来估算大规模的水力扩散率和地壳中的应力状态。我们用高海拔地区径流为主的河流中的流量来估算地下水补给量的季节性变化。我们对地震数N，地震矩M_o和水流流量Q的时间序列进行插值，并确定在Q与N和M_o之间的等效频带处的互相关系数。我们发现平均时间滞后约151天具有统计学意义的相关系数。在周期性（1年）边界条件下，该时滞和平均地震深度约为4.5 km，用于求解压力扩散方程，以估计k≈10〜（-1）m〜2 /的水力扩散率。 s时，水力传导率约为k_h≈10〜（-7）m / s，渗透率约为k≈10〜（-15）m〜2。周期性边界条件还使我们能够确定在平均地震深度必须达到的所施加的近表面孔隙流体压力扰动P_0 /≈0.1 MPa的临界孔隙流体压力分数P'/ P_0≈0.1引起水震。 P'≈0.01 MPa的低值与提出0.01≤P'≤0.1 MPa的其他研究一致，并暗示了Mt附近地壳的应力状态。胡德可能对失败至关重要。因此，我们得出的结论是，尽管全年发生山地震。胡德山沿南部先前存在的断层的地震活动水平升高。有效压力的减少会在水文上诱导夏季的抽烟。

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