We document the arrival of seismic energy in the core shadow zone up to large distances beyond 150° more than 100 s prior to the core phases. Numerical simulations of the energy transport in an established heterogeneity model show that scattering throughout the entire mantle explains these observations. Diffraction at the core-mantle boundary is unlikely in our 1–2 Hz frequency band and is not required indicating misleading terminology with reference to P_diff for the scattered P∗P-energy. Records of the largest deep earthquakes at low-noise stations are key to the observation of the faint precursory signal which changes appearance with increasing distance from a coda-like decay over a constant amplitude level around 130° to an emergent wave train. According to our simulations, different depth layers in the mantle dominate different time-distance windows of the scattered wave train, providing the opportunity to improve the depth resolution of mantle heterogeneity models.

中文翻译：

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P 波在整个地幔中的散射如何模拟高频 Pdiff 及其尾波


我们记录了地震能量在岩心阶段之前 100 秒以上到达岩心阴影区的远距离（超过 150°）。在已建立的异质性模型中对能量传输的数值模拟表明，整个地幔的散射解释了这些观察结果。在我们的 1-2 Hz 频段中，核幔边界处的衍射不太可能出现，并且不需要指示关于散射 P*P 能量的 P _diff 的误导性术语。低噪声台站最大深部地震的记录是观察微弱前兆信号的关键，该前兆信号的外观随着距离的增加而变化，从大约 130° 恒定振幅水平的尾波衰变到出现的波列。根据我们的模拟，地幔中的不同深度层主导着散射波列的不同时间-距离窗口，为提高地幔非均质性模型的深度分辨率提供了机会。