Slow-slip events frequently occur, but regular earthquakes are much less active on the H2O fluid-rich subduction interface at depths of ~ 40 km. The characteristic duration for silent earthquakes, which are categorized as the great slow-slip events, is more than five orders of magnitude longer than that for regular earthquakes. Such phenomena are often attributed to the slippage of the softer part of the subduction interface, but the impact of H2O fluid on aseismic slip is still unsolved. Here, we conduct deformation experiments on water-saturated harzburgite at pressures of 1.2 to 3.0 GPa and temperatures of 770 to 1250 K, corresponding to the conditions of the lower part of the overriding plate just above the subduction interface. We observe deformation of the harzburgite followed by silent faulting at a significantly low stress level down to 0.3 GPa under fluid-bearing conditions, even though many acoustic emissions are generated at the onset of faulting in fluid-free harzburgite. We find that the observed silent faulting is caused by the detachment of asperity contacts by high pore pressures and lubrication of the fault plane by a hydration reaction. We therefore propose that H2O fluid may prevent the occurrence of regular intraslab earthquakes, but trigger silent earthquakes.

中文翻译：

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在上地幔压力下由 H2O 流体诱导的菱镁矿从地震断层转变为无声滑动

慢滑事件经常发生，但在约 40 公里深度的富含 H2O 流体的俯冲界面上，常规地震的活动要少得多。被归类为大慢滑事件的无声地震的特征持续时间比常规地震长五个数量级以上。这种现象通常归因于俯冲界面较软部分的滑移，但H2O流体对抗震滑移的影响仍未得到解决。在这里，我们在 1.2 到 3.0 GPa 的压力和 770 到 1250 K 的温度下对水饱和的斜方辉石进行变形实验，对应于俯冲界面正上方的上覆板块下部的条件。我们观察到菱镁矿的变形，然后是在低至 0 的显着低应力水平下无声断层。在含流体条件下为 3 GPa，尽管在无流体的菱镁矿中在断层开始时会产生许多声发射。我们发现观察到的无声断层是由高孔隙压力引起的粗糙接触分离和水化反应对断层平面的润滑引起的。因此，我们提出 H2O 流体可能会阻止常规板内地震的发生，但会引发无声地震。