The Pressure‐ and Temperature‐Dependence of Thermal Pressurization in Localized Faults
The Pressure‐ and Temperature‐Dependence of Thermal Pressurization in Localized Faults
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DOI：
10.1029/2023jb026558
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发表时间：
2023-08
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影响因子：
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通讯作者：
N. Badt;C. Huber;G. Hirth;T. Tullis
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作者：
N. Badt;C. Huber;G. Hirth;T. Tullis
预计热加压（TP）是地震期间重要的动摩擦减弱机制。然而，主流模型假设断层带中流体饱和岩石的物理、热和水力特性在 TP（恒定情况）期间保持恒定，这本质上涉及温度和压力的变化。我们用一维数值模型（变量情况）求解饱和断层带的压力和温度相关的物理、热力和水力参数的一般形式的 TP 控制方程。该模型考虑了平面上恒定速率的滑动，因此没有考虑动态摩擦破裂的情况。根据 Frederick 辉绿岩、Westerly 花岗岩和 Hanaore 断层泥的实验数据，我们测试了 10−22–10−16 m2 的介质渗透率和 0.5%–17% 的孔隙率。我们发现，由于流体加压系数和水力扩散率的增加，低渗透率（<10−20 m2）和低孔隙率（<1%）断层岩石的两种情况下预测的剪切应力下降和温度上升相似。两个模型之间的差异在渗透性和多孔性更强的断层岩中很明显。 TP 期间水力扩散率的增加导致扩散长度在可变情况下随 time0.7 变化。此外，我们的计算表明，重要的是应用具有环境初始条件的常量案例模型来模拟断层带，而不是旨在表示 TP 期间发生的温度和压力变化的时间平均值。
Thermal pressurization (TP) is predicted to be an important dynamic frictional weakening mechanism during earthquakes. The prevailing models, though, assume that the physical, thermal and hydraulic properties of the fluid‐saturated rock in the fault zone are constant during TP (the constant case) which inherently involves temperature and pressure changes. We solve the governing equations for TP in their general form with pressure‐ and temperature‐dependent physical, thermal and hydraulic parameters of a saturated fault zone with a one‐dimensional numerical model (the variable case). The model considers slip on a plane at a constant rate, and so does not account for dynamic frictional rupture scenario. We test a wide range of medium permeabilities of 10−22–10−16 m2 and porosities 0.5%–17%, based on experimental data for Frederick diabase, Westerly granite and the Hanaore Fault gouge. We find that the predicted shear stress drop and temperature rise is similar between the two cases for low permeability (<10−20 m2) and low porosity (<1%) fault rocks, owing to an increase in the fluid pressurization factor and hydraulic diffusivity. Differences between the two models are evident in more permeable and porous fault rocks. The increase in hydraulic diffusivity during TP results in a diffusional length which scales with time0.7 in the variable case. In addition, our calculations show that it is important to apply the constant case model with the ambient initial conditions for the modeled fault zone and not time‐averaged values that aim to represent the temperature and pressure changes that occur during TP.