We measured inner core normal mode pair ₁₀S₂-₁₁S₂, which cross-couples strongly for 1D structure and is sensitive to shear wave velocity, and find that our measurements agree with a strongly attenuating inner core. In the past, this mode pair has been used to try to resolve the debate on whether the inner core is strongly or weakly attenuating. Its large spectral amplitude in observed data, possible through the apparent low attenuation of ₁₀S₂, has been explained as evidence of a weakly attenuating inner core. However, this contradicted body waves and other normal modes studies, which resulted in this pair of modes being excluded from inner core modelling. Modes ₁₀S₂ and ₁₁S₂ are difficult to measure and interpret because they depend strongly on the underlying 1D model used. This strong dependence makes these modes change both their oscillation characteristics and attenuation values under a small 1D perturbation to the inner core model. Here, we include this effect by allowing the pair of modes to cross-couple or resonate through 1D structure and treat them as one hybrid mode. We find that, unlike previously thought, the source of ₁₀S₂ visibility is its strong cross-coupling to ₁₁S₂ for both 1D elastic and anelastic structure. We also observe that the required 1D perturbation is much smaller than the 2% v_s perturbation previously suggested (Andrews et al. 2006), because we simultaneously measure 3D structure in addition to 1D structure. Only a 0.5% increase in inner core v_s or a 0.5% decrease in inner core radius is required to explain ₁₀S₂-₁₁S₂ observations and a weakly attenuating inner core is not needed. In addition, the 3D structure measurements of mode ₁₀S₂ and its cross-coupling to ₁₁S₂ show the typical strong zonal splitting pattern attributed to inner core cylindrical anisotropy, allowing us to add further constrains to deeper regions of the inner core.

中文翻译：

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通过测量强耦合正常模式对来约束一维内核衰减

我们测量内芯正常模式对₁₀ š ₂ - ₁₁小号₂，该交叉耦合极力为1D结构，并且是剪切波速度敏感的，并且发现，我们的测量同意用强衰减的内芯。过去，使用这种模式对来解决有关内核是强衰减还是弱衰减的争论。通过观察到的₁₀ S ₂的明显低衰减，它在观测数据中的大光谱振幅已被解释为内核弱衰减的证据。但是，这与体波和其他正常模式研究相矛盾，导致这对模式被排除在内核模型之外。模式₁₀S ₂和₁₁ S ₂很难测量和解释，因为它们很大程度上取决于所使用的基础一维模型。这种强烈的依赖性​​使得这些模式在对内芯模型的一维微扰下，既可以改变其振荡特性，又可以改变衰减值。在这里，我们通过允许一对模式通过一维结构交叉耦合或共振并将它们视为一个混合模式来包括这种效果。我们发现，与以前的想法不同，对于1D弹性和非弹性结构，₁₀ S ₂可见性的来源是其与₁₁ S _2的强交叉耦合。我们还观察到，所需的一维扰动远小于2％v _s摄动先前建议（Andrews等人2006），因为除了1D结构外，我们还同时测量3D结构。仅在内侧芯增加了0.5％v_小号或内芯半径的0.5％的降低是必需的来解释₁₀小号₂ - ₁₁ s ^ _2周的观察和不需要弱衰减内芯。此外，模式₁₀ S ₂的3D结构测量及其与₁₁ S _2的交叉耦合显示了归因于内芯圆柱各向异性的典型强区域分裂图案，这使我们可以对内芯的较深区域添加更多约束。