Changes of Event Size Distribution During Episodes of Shallow Tectonic Tremor, Nankai Trough
Changes of Event Size Distribution During Episodes of Shallow Tectonic Tremor, Nankai Trough
复制标题
南海海槽浅层构造震发作期间事件大小分布的变化
DOI：
10.1029/2020gl092011
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发表时间：
2021
影响因子：
5.2
通讯作者：
Yabe Suguru
中科院分区：
文献类型：
--
作者：
Nakano Masaru;Yabe Suguru
慢震遵循幂律大小分布，最大地震呈指数锥形分布。我们研究了南开海槽两次长时间地震活动（bbb10 - 1个月）中浅层构造地震事件的大小分布变化，发现随着地震活动的减弱，每次地震活动的后期，大小分布的斜率增大，而截止震级减小。用二维慢震概率元胞自动机模型解释这些变化，我们发现滑动过程中事件点火概率的降低或能量耗散的增加可以定性地解释观测到的变化。这些变化表明，每次地震发生时，断层界面上的累积应力或孔隙流体压力都有所减少。由于震源在一次地震中有迁移，震源大小分布参数的变化可归因于震源特征的空间变化或时间变化。
Slow earthquakes follow a power‐law size distribution with an exponential taper for the largest events. We investigated changes in the size distribution of shallow tectonic tremor events during two prolonged tremor episodes (>1 month) along the Nankai trough and found that the slope of the size distributions increased while the cut‐off magnitudes decreased late during each episode, as tremor activity waned. Interpreting these changes with the two‐dimensional probabilistic cell automaton model of slow earthquakes, we found that a decrease in event ignition probability or an increase in energy dissipation during slip can qualitatively explain the observed changes. These changes imply that a decrease in accumulated stress or pore‐fluid pressure on the fault interface occurred during each tremor episode. Because the tremor source migrates during an episode, the changes in the size distribution parameters can be attributed to spatial variations or temporal changes in the source characteristics.