| 2011年日本MW9.0地震引发的海啸对地震背景噪声的影响 |
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| 引用本文： | 陈斐,薛梅.2011年日本MW9.0地震引发的海啸对地震背景噪声的影响[J].地震学报,2021,43(3):321-337. |
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| 作者姓名： | 陈斐 薛梅 |
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| 作者单位： | 中国上海 200092 同济大学海洋地质国家重点实验室 |
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| 基金项目： | 国家自然科学基金（42076064）资助 |
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| 摘 要： | 基于北美沿岸和内陆地震台站的连续地震波形记录，并结合沿岸台站附近布设的DART系统记录的海底压力数据以及预测潮汐数据，利用时频分析和极化分析方法对2011年3月11日日本东北部海域MW9.0大地震所激发的海啸对地震背景噪声所产生的影响予以深入分析。结果显示:海啸对高频噪声（1.3—1.5 Hz）以及短周期双频微地动噪声（0.18—0.4 Hz）的影响较小，但海啸显著增强了长周期双频微地动（0.1—0.15 Hz）、单频微地动（0.05—0.08 Hz）以及地球背景自由振荡（0.004—0.007 Hz）的振幅，且随着噪声频率的降低，这种振幅增强的影响更明显，影响的持续时间也更长；海啸到达近岸时，对附近台站的各频段噪声均有影响，成为各频段噪声的主控能量来源，且其位置在后续过程中会随时间变化。这表明海啸对噪声特征的影响与海啸传播特性有关，即海啸在传播过程中因受水深、海底地形以及近岸地形的反射、衍射等的影响，能量聚集区域随时间而变化，并非均匀地传播到海岸， 从而导致了不同频带噪声主极化方向随时间的变化。
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| 关 键 词： | 海啸 2011年日本MW9.0地震 地震背景噪声 地球背景自由振荡 微地动 |
| 收稿时间： | 2020-10-23 |
Impact of the tsunami excited by the 2011 MW9.0 Japan earthquake on seismic ambient noises |
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| Chen Fei,Xue Mei.Impact of the tsunami excited by the 2011 MW9.0 Japan earthquake on seismic ambient noises[J].Acta Seismologica Sinica,2021,43(3):321-337. |
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| Authors: | Chen Fei Xue Mei |
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| Affiliation: | State Key Laboratory of Marine Geology，Tongji University，Shanghai 200092，China |
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| Abstract: | The MW9.0 earthquake on March 11, 2011 occurred in the northeastern sea of Japan triggered a catastrophic tsunami, which had significant influences on the seismic ambient noises with ocean-lithosphere coupling. This study uses the continuous data recorded by seismic stations along the coast and inland of North America, combined with the seafloor pressure data recorded by the DART system nearby, as well as the predicted tidal data to analyze the impact of this tsunami on the seismic ambient noises by using time-frequency analysis and polarization analysis methods. The results show that this tsunami had little impact on the high-frequency noise （1.3?1.5 Hz） and short-period double-frequency microseisms （0.18?0.4 Hz）, while it significantly enhanced the amplitudes of long-period double-frequency microseisms （0.1?0.15 Hz）, single-frequency microseisms （0.05?0.08 Hz）, as well as the Earth’s background free oscillations （0.004?0.007 Hz）. Moreover, as the frequency of the ambient noise decreases, the amplitude enhancement becomes more pronounced and lasts longer. When the tsunami reaches the shore, it has an impact on the ambient noise of coastal stations nearby for all three frequency-bands of Earth’s background free oscillations, microseisms, and high-frequency noise and becomes the main energy source of seismic ambient noises at all three frequency bands. And the position of the dominant tsunami sources changes with time. All above-mentioned suggests that the influence of tsunami on seismic ambient noise is related to the propagation characteristics of tsunami, that is, due to the influence of water depth, reflections and diffractions of seafloor and inshore topography, the energy accumulation area changes with time, and the energy does not propagate uniformly to the coast, resulting in the changes of dominant polarization direction of seismic ambient noise in different frequency bands with time. By cross-disciplines of seismology and oceanography, this study is of significance for advancing studies on the coupling mechanism of ocean-lithosphere, identifying the characteristics of tsunami waves from the perspective of seismology, as well as exploring new tsunami warning mechanisms. |
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