Precise Monitoring of Pore Pressure at Boreholes Around Nankai Trough Toward Early Detecting Crustal Deformation
Precise Monitoring of Pore Pressure at Boreholes Around Nankai Trough Toward Early Detecting Crustal Deformation
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DOI：
10.3389/feart.2021.717696
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发表时间：
2021-08
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通讯作者：
K. Ariyoshi;T. Kimura;Y. Miyazawa;S. Varlamov;T. Iinuma;A. Nagano;J. Gomberg;E. Araki;T. Miyama;K. Sueki;S. Yada;T. Hori;N. Takahashi;S. Kodaira
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作者：
K. Ariyoshi;T. Kimura;Y. Miyazawa;S. Varlamov;T. Iinuma;A. Nagano;J. Gomberg;E. Araki;T. Miyama;K. Sueki;S. Yada;T. Hori;N. Takahashi;S. Kodaira
在我们最近的研究中，我们在2020年3月在两个钻孔站（C0002和C0010）发现了由于慢速滑移事件（SSE）引起的孔隙压力变化，在那里，另一个井眼（C0006）接近南卡槽，似乎并不是因为在海底上引用压力的仪器漂移，以消除潮汐和海洋波动之类的非密封性变形。为了克服这个问题，我们使用电缆网络密集的海底网络系统的海底压力表进行地震和海啸（捐赠）站附近的钻孔站，而不是通过引入它们之间的时间滞后。我们确认时间滞后是从理论潮汐模式的叠加中解释的。通过将此方法应用于SSE期间的孔隙压力，我们发现C0006的孔隙压力变化约为0.6 hpa。我们还研究了海底因海洋波动而根据海洋建模而对海底压力的影响，这表明，从黑鲁道蜿蜒曲折地解释了从发作到终止SSE终止的有效正常应力的减少，并可能促进更新的滑移迁移，并促进更新如在Hikurangi俯冲带中观察到的，短期海洋波动的有效正常应力增加可能终止SSE。
In our recent study, we detected the pore pressure change due to the slow slip event (SSE) in March 2020 at the two borehole stations (C0002 and C0010), where the other borehole (C0006) close to the Nankai Trough seems not because of instrumental drift for the reference pressure on the seafloor to remove non-crustal deformation such as tidal and oceanic fluctuations. To overcome this problem, we use the seafloor pressure gauges of cabled network Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET) stations nearby boreholes instead of the reference by introducing time lag between them. We confirm that the time lag is explained from superposition of theoretical tide modes. By applying this method to the pore pressure during the SSE, we find pore pressure change at C0006 about 0.6 hPa. We also investigate the impact of seafloor pressure due to ocean fluctuation on the basis of ocean modeling, which suggests that the decrease of effective normal stress from the onset to the termination of the SSE is explained by Kuroshio meander and may promote updip slip migration, and that the increase of effective normal stress for the short-term ocean fluctuation may terminate the SSE as observed in the Hikurangi subduction zone.