The presence of pressurized fluids influences the mechanical behavior of faults. To test the roles of normal stress and fluid pressure on shear strength and localization behavior of calcite gouges, we conducted a series of rotary‐shear experiments with pore fluid pressures up to 10.5 MPa and difference between normal stress and fluid pressure up to 11.2 MPa. Calcite gouges were sheared for displacements of 0.3 m to several meters at slip rates of 1 mm/s and 1 m/s. Drainage conditions in experiments were constrained from estimates of the hydraulic diffusivity. Gouges were found to be drained at 1 mm/s, but possibly partially undrained during sliding at 1 m/s. Shear strength obeys an effective‐stress law with an effective‐stress coefficient close to unity with a friction coefficient of ~0.7 that decreases to 0.19 due to dynamic weakening. The degree of comminution and slip localization constrained from experimental microstructures depends on the effective normal stress. Slip localization in calcite gouges does not occur at low effective normal stress. The presence of pore fluids lowers the shear strength of gouges sheared at 1 mm/s and causes an accelerated weakening at 1 m/s compared to dry gouges, possibly due to enhanced subcritical crack growth and intergranular lubrication. Thermal pressurization occurs only after dynamic weakening when friction is generally low and relatively independent of normal stress and therefore unaffected by thermal pressurization. The experimental results are consistent with the view that the presence of pressurized fluid in carbonate‐bearing faults can facilitate earthquake nucleation.

中文翻译：

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有效应力和孔隙流体压力对碳酸盐岩滑动带断层强度和滑动定位的影响

加压流体的存在会影响断层的机械行为。为了测试正应力和流体压力对方解石凿的抗剪强度和定位行为的影响，我们进行了一系列旋转剪切实验，孔隙流体压力高达10.5 MPa，正应力和流体压力之差高达11.2 MPa。方解石切碎机以1 mm / s和1 m / s的滑移速度剪切0.3 m至数米的位移。实验中的排水条件受水力扩散率的估计约束。发现凿子以1 mm / s的速度排水，但在滑动过程中以1 m / s的速度可能部分排水。剪切强度服从有效应力定律，有效应力系数接近于一，摩擦系数为〜0.7，由于动力减弱而减小至0.19。受实验微观结构限制的粉碎程度和滑移定位程度取决于有效法向应力。在低有效法向应力下不会发生方解石凿中的滑移定位。孔隙流体的存在降低了以1 mm / s剪切的切槽的剪切强度，与干切槽相比，以1 m / s的速度导致了加速减弱，这可能是由于亚临界裂纹扩展和晶间润滑的缘故。仅当动力通常减弱且摩擦力通常较低且相对独立于法向应力且因此不受热加压影响时，才在动态减弱之后发生热加压。实验结果与以下观点一致：在含碳酸盐岩断层中存在加压流体可以促进地震成核。