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首页> 外文期刊>Pure and Applied Geophysics >Normal Mode Energetics for Far-field Tsunamis Generated by Dislocations and Landslides
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Normal Mode Energetics for Far-field Tsunamis Generated by Dislocations and Landslides

机译：位错和滑坡产生的远场海啸的普通模式能量学

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— We apply the normal mode representation of tsunami waves, as introduced by Ward (1980) to the systematic study of the excitation of far-field tsunamis by both dislocation sources (represented by double-couples of moment M 0), and landslides (represented by single forces). Using asymptotic representations of the continuation of the tsunami eigenfunction into the solid Earth, we derive analytical expressions of the spectral amplitude generated by both systems. We show that the quadrupolar corrections defined by Dahlen (1993) in the case of landslides can result in an increase of 1 to 2 orders of magnitude of the effective force. Even so, the spectrum of tsunami waves generated by landslides is found to be offset significantly to relatively high frequencies (10 mHz), where dispersion becomes important and eventually diminishes time-domain amplitudes. We proceed to calculate the total energy delivered into the tsunami modes by integrating the energy of multiplets for an average source geometry. In the case of dislocation sources, and taking into account the corner frequency of the source, we reproduce the scaling with M 0 4/3 which was derived from purely static arguments by Kajiura (1981). We compare the directivity patterns of far-field tsunami waves by dislocations and landslides, and conclude that the latter cannot give rise to pronounced lobes of directivity for physically acceptable values of the velocity of the slide. Directivity thus constitutes a robust discriminant of the nature of the source which, when applied to the 1946 Aleutian tsunami in the far-field, requires generation by a dislocative source.
机译：—我们将Ward（1980）引入的海啸波的正态模态表示法用于两种位错源（以矩M 0的双偶数表示）对远场海啸激发的系统研究，和滑坡（由单力代表）。使用将海啸本征函数延续到固体地球的渐近表示，我们得出了两个系统产生的频谱幅度的解析表达式。我们表明，Dahlen（1993）在滑坡的情况下定义的四极校正可导致有效力增加1到2个数量级。即使这样，发现由滑坡产生的海啸波的频谱也被明显地偏移到了相对较高的频率（10 mHz），在该频率上色散变得很重要，并最终减小了时域振幅。我们通过对平均源几何形状的多重能量进行积分来计算向海啸模式输送的总能量。对于位错源，并考虑到源的转折频率，我们用Kajiura（1981）的纯静态论证再现了M 0 4/3 的缩放比例。我们通过位错和滑坡比较了远场海啸波的方向性模式，并得出结论，对于滑坡速度的物理可接受值，后者不能引起明显的方向性波瓣。因此，方向性构成了震源性质的强有力的判别力，当应用于远场的1946年阿留申海啸时，需要由易位震源产生。

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