Tsunami waveform inversion including dispersive waves: the 2004 earthquake off Kii Peninsula, Japan
Tsunami waveform inversion including dispersive waves: the 2004 earthquake off Kii Peninsula, Japan
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DOI：
10.1029/2009jb006884
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发表时间：
2010-06-03
影响因子：
3.9
通讯作者：
Furumura, Takashi
中科院分区：
文献类型：
--
作者：
Saito, Tatsuhiko;Satake, Kenji;Furumura, Takashi
长波通常被认为是海啸的模型，但大的海底地震产生的初始水高分布的波长，特别是在垂直于断层走向的方向上，有时并不比水深大多少。由此产生的海啸可能具有一种色散特征，无法用传统的长波近似来模拟。2004年日本南部海岸的纪井半岛地震（里氏7.4级）确实产生了分散的海啸，四国附近的两个监测站都记录到了这一点。而对于7.1级前震，这些台站没有识别出主要的弥散性海啸。由于频散波对断层走向有很强的方向性依赖，上述差异表明主震和前震的走向不同。基于弥散海啸方程进行了海啸波形反演分析，估算了主震初始水高分布。估算的初始水高分布与余震区重叠，表明断层走向垂直于槽轴，总排水量为1.7 ~ 2.0 × 10(9) m(3)。当我们使用传统的长波近似时，估计的初始水高分布大大超出了余震区，因为在余震区之外需要人工震源来再现观测到的色散波。
Long waves are often assumed to model tsunamis, but the wavelength of the initial water height distribution produced by a large submarine earthquake, particularly in the direction perpendicular to the fault strike, is sometimes not much greater than the water depth. The resulting tsunami may have a dispersive character that cannot be simulated based on a conventional long-wave approximation. The 2004 earthquake off Kii Peninsula (M 7.4) on the southern coast of Japan indeed produced a dispersive tsunami that was recorded at two stations located off Shikoku. For the foreshock (M 7.1), on the contrary, a dominant dispersive tsunami was not recognized at these stations. Because dispersive waves show strong directional dependence with respect to the fault strike, the above difference indicates that the strikes of the main shock and the foreshock were different. We conducted a tsunami waveform inversion analysis based on the dispersive tsunami equations to estimate the initial water height distribution of the main shock. The estimated initial water height distribution overlapped with the aftershock region, suggesting that the fault strike was perpendicular to the trough axis, and the total displaced water volume was 1.7 - 2.0 x 10(9) m(3). When we used the conventional long - wave approximation, the estimated initial water height distribution extended considerably from the aftershock area, because artificial sources were needed outside the aftershock area to reproduce the observed dispersive waves.