Tsunami signals from the 2006 and 2007 Kuril earthquakes detected at a seafloor geomagnetic observatory
Tsunami signals from the 2006 and 2007 Kuril earthquakes detected at a seafloor geomagnetic observatory
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DOI：
10.1029/2010jb007873
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发表时间：
2011-02-24
影响因子：
3.9
通讯作者：
Goto, Tadanori
中科院分区：
文献类型：
--
作者：
Toh, Hiroaki;Satake, Kenji;Goto, Tadanori
西北太平洋海底地磁观测站探测到了与沿着千岛海沟发生的两次地震的海啸通道相关的明显电磁（EM）变化。以往的地震学分析表明，2006年11月15日发生的8.3级地震是海沟向陆坡上的俯冲型地震，而2007年1月13日发生的8.1级地震是海沟向海一侧的正断层型地震。电磁测量能够精确监测海啸传播方向以及海水的粒子运动。2006年和2007年的海啸，在初始运动和分散的字符，是一致的水动力学模拟结果的水平水速度的估计显着不同。也就是说，海啸引起的水平地磁分量显示出相反的符号的上升和撤退波从“电流壁假说”的预期。“2007年的海啸地震的分散效应更为显著，其海啸地震的震源区较小。因此，2007年的海啸倾向于违反长波近似。在我们的数值模拟中，需要Boussinesq近似来再现2007年事件的色散特征。在海啸预报方面，EM传感器相对于传统海啸传感器（如海底压力计）的一个重要优势是它们的矢量测量能力：除了它们监测粒子运动的能力之外，向下磁分量的第一个峰值总是先于海啸峰值，这表明如果矢量EM传感器集成到现有系统中，全球海啸预警系统将得到显着改善。
A seafloor geomagnetic observatory in the northwest Pacific detected clear electromagnetic (EM) variations associated with tsunami passage from two earthquakes that occurred along the Kuril Trench. Previous seismological analyses indicated that the M8.3 earthquake on 15 November 2006 was an underthrust type on the landward slope of the trench, while the M8.1 earthquake on 13 January 2007 was a normal fault type on the seaward side. The EM measurements enabled precise monitoring of the tsunami propagation direction as well as particle motion of the seawater. The estimated horizontal water velocity differs significantly for the 2006 and 2007 tsunamis, in terms of initial motion and dispersive characters, being consistent with the hydrodynamic simulation results of the tsunamis. Namely, the tsunami-induced horizontal geomagnetic components showed opposite signs for the rise and retreat waves as expected from the "electric current wall hypothesis." The dispersion effect is more remarkable in the 2007 event with a smaller source region of its tsunamigenic earthquake. The 2007 tsunamis, therefore, tend to violate the long-wave approximation. The Boussinesq approximation was required to reproduce the dispersive character of the 2007 event in our numerical simulation. In terms of tsunami forecast, an important advantage of EM sensors over conventional tsunami sensors, such as seafloor pressure gauges, is their capability of vector measurements: in addition to their ability to monitor particle motions, the first peak of the downward magnetic component always precedes the tsunami peak, suggesting a significant improvement in global tsunami warning systems if vector EM sensors are integrated into the existing systems.