The role of solid Earth tide in fault reactivation has significant implications for understanding earthquake triggering, carbon sequestration, and the global carbon budget. Despite extensive research on this topic, the relationship between Earth tide and fault reactivation remains unclear. In this study, we investigate the influence of solid Earth tide on the reactivation of sub-seabed faults, which may lead to the release of methane. We monitored the sub-seabed temperature and pore-fluid pressure at two sites on a fault system located in the Black Sea. Two sets of data obtained from distinct periods revealed inconsistent results. For the first set of data and despite the distance between the two sites (∼790 m), the responses in terms of temperature and pore pressure changes were synchronous (September 2021). We showed from these data that the presence of over-pressured fluid promotes fault reactivation under Earth tide cycles, resulting in synchronized degassing events. For the second set of data recorded from the same two sites (September 2021–May 2023), we did not identify any concomitance between Earth tides and the monitored parameters. Our analyses show that discrepancies in observations could be related to the fluid discharge/recharge process. The fluid discharge observed during the first period resulted in a decrease in excess pore-pressure, making the fault insensitive to Earth tides during the subsequent recharge period. Our data also sheds light on conflicting literature results, suggesting that the interaction between faults and Earth tides primarily depends on fluid pore pressure, a parameter rarely measured.

中文翻译：

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地潮在重新激活浅层断层和触发海底甲烷排放中的作用


固体地球潮汐在断层再激活中的作用对于理解地震触发、碳封存和全球碳收支具有重要意义。尽管对这一主题进行了广泛的研究，但地球潮汐与断层再激活之间的关系仍不清楚。在这项研究中，我们研究了固体地球潮汐对海底断层重新激活的影响，这可能导致甲烷的释放。我们在位于黑海的断层系统上监测了两个地点的海底温度和孔隙流体压力。从不同时期获得的两组数据揭示了不一致的结果。对于第一组数据，尽管两个站点之间的距离 （∼790 m），但温度和孔隙压力变化方面的响应是同步的（2021 年 9 月）。我们从这些数据中表明，在地球潮汐循环下，过压流体的存在会促进故障重新激活，从而导致同步脱气事件。对于从同一两个站点（2021 年 9 月至 2023 年 5 月）记录的第二组数据，我们没有发现地球潮汐与监测参数之间存在任何伴随关系。我们的分析表明，观察结果的差异可能与液体排放/补给过程有关。在第一阶段观察到的流体排放导致超孔隙压力降低，使断层在随后的补给期间对地球潮汐不敏感。我们的数据还揭示了相互矛盾的文献结果，表明断层和地球潮汐之间的相互作用主要取决于流体孔隙压力，而这个参数很少被测量。