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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Seismic evidence of fluid migration in northeastern Japan after the 2011 Tohoku-Oki earthquake
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Seismic evidence of fluid migration in northeastern Japan after the 2011 Tohoku-Oki earthquake

机译：2011年东北东北地震后日本东北部流动迁移的地震证据

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摘要

We use ambient-noise-based seismic monitoring to detect an anomalous seismic velocity decrease (similar to 0.01%) widely distributed in Honshu that arose about 1 year after the 2011 M-w 9.0 Tohoku-Oki earthquake. The anomaly is located along the central quaternary volcanic axis, and it suggests that the changes are related to volcanic processes. After correction for possible external environmental forcing-related velocity changes, the anomaly in the seismic velocity remains, which implies that it is associated with some internal physical process. We show a general strong positive correlation between the seismic velocity changes and the intensity of ground motion derived from the daily cumulative seismic moment. However, the lack of correlation during the anomaly itself reveals that this reduction is not directly caused by earthquake shaking. Tiltmeter low-pass observations show temporal variations that are correlated with the velocity changes. These observations strengthen the hypothesis of actual physical deformation. A previously reported decrease in fault strength (similar to 10%) for the same period as the velocity anomaly further supports a physical property change in the upper crust. We also note a simultaneous increase in activity of low-frequency events in the volcanic area, which suggests an increase in pore pressure in the upper crust. We propose that the observed anomalous seismic velocity decrease in early 2012 is due to an increase in pore pressure induced by an upward fluid migration, which at the same time triggered the increase in fluid-driven swarm seismicity and low-frequency events. We recall the depth-dependent seismic velocity changes in Honshu and derive an average diffusion of 1 m(2)/s over around 11 months after the Tohoku-Oki earthquake. (C) 2021 Elsevier B.V. All rights reserved.
机译：我们使用基于环境噪声的地震监测来检测广泛分布在本州的异常地震速度下降（类似于0.01%），这是在2011年东北奥基9.0级M-w地震后约一年发生的。该异常位于中央第四纪火山轴上，表明其变化与火山作用有关。在对可能的外部环境强迫相关速度变化进行校正后，地震速度中的异常仍然存在，这意味着它与某些内部物理过程有关。我们展示了地震速度变化与由每日累积地震矩得出的地面运动强度之间的强正相关。然而，异常本身缺乏相关性表明，这种减少并不是由地震震动直接造成的。倾斜仪的低通观测显示了与速度变化相关的时间变化。这些观察结果加强了实际物理变形的假设。与速度异常同期，先前报告的断层强度下降（类似于10%）进一步支持了上地壳的物理性质变化。我们还注意到火山区低频事件的活动同时增加，这表明上地壳的孔隙压力增加。我们认为，2012年初观测到的异常地震速度下降是由于流体向上迁移引起的孔隙压力增加，同时触发了流体驱动的群体地震活动和低频事件的增加。我们回顾了本州与深度相关的地震速度变化，并得出了东北奥基地震后大约11个月的平均扩散速度为1m（2）/s。（c）2021爱思唯尔B.V.保留所有权利。

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