Widespread seismicity excitation throughout central Japan following the 2011 M=9.0 Tohoku earthquake and its interpretation by Coulomb stress transfer
Widespread seismicity excitation throughout central Japan following the 2011 M=9.0 Tohoku earthquake and its interpretation by Coulomb stress transfer
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DOI：
10.1029/2011gl047834
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发表时间：
2011-04
影响因子：
5.2
通讯作者：
S. Toda;R. Stein;Jian Lin
中科院分区：
文献类型：
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作者：
S. Toda;R. Stein;Jian Lin
我们报告了在M=9.0的东北主震之后，日本内陆、日本海和伊豆群岛的部分地区发生的M ≥ 2级地震的地震活动率出现了前所未有的大范围增加，这些地震发生在距大逆冲断层上的高地震滑动（≥15 m）的位置425 km处。2004年苏门答腊9.1级或2010年智利8.8级地震没有出现这种增加，但它们缺乏检测这种小事件所需的地震网络。在这里，我们探讨的可能性，速率的变化是静态库仑应力转移到小断层的产品。我们使用M ≥ 3.5地震的节面作为这种小的活动断层的替代物，发现在15个平均大小为80 × 80 km的区域中，11个显示出计算的应力变化与观测到的地震活动率变化之间的正相关性，3个显示出负相关性，其中一个变化太小而无法评估。这项工作表明，地震活动可以在主震的名义应力阴影打开，只要小的几何形状不同的活动断层存在，这可能是很常见的。
We report on a broad and unprecedented increase in seismicity rate following the M=9.0 Tohoku mainshock for M ≥ 2 earthquakes over inland Japan, parts of the Japan Sea and Izu islands, at distances of up to 425 km from the locus of high (≥15 m) seismic slip on the megathrust. Such an increase was not seen for the 2004 M=9.1 Sumatra or 2010 M=8.8 Chile earthquakes, but they lacked the seismic networks necessary to detect such small events. Here we explore the possibility that the rate changes are the product of static Coulomb stress transfer to small faults. We use the nodal planes of M ≥ 3.5 earthquakes as proxies for such small active faults, and find that of fifteen regions averaging ∼80 by 80 km in size, 11 show a positive association between calculated stress changes and the observed seismicity rate change, 3 show a negative correlation, and for one the changes are too small to assess. This work demonstrates that seismicity can turn on in the nominal stress shadow of a mainshock as long as small geometrically diverse active faults exist there, which is likely quite common.