The current set of reference models for the radial variation of Earth structure have been in use for several decades, and provide a good representation of many aspects of the seismic wavefield. Nevertheless, strong constraints from the differential times between pairs of SmKS phases indicate the need to modify the P wave speed profile in the upper part of the outer core. In order to incorporate such a change and maintain the representation of the full suite of seismic phases compensatory adjustments have to be made, dominantly in the mantle. Using multi-objective optimization, a new preferred radial model ek137 has been generated that provides a good representation of the traveltimes of all core phases. An adiabatic profile can be maintained through most of the outer core, but departures are needed at the base, as in the ak135 model. The latest estimates for inner core shear wave speed are included in ek137.

中文翻译：

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重访径向地球模型

当前用于地球结构径向变化的参考模型集已经使用了几十年，并且很好地表示了地震波场的许多方面。尽管如此，成对的SmKS相之间的差分时间的强烈约束表明需要修改外芯上部的P波速度剖面。为了纳入这样的变化并保持整套地震相的表示，必须在地幔中进行补偿性调整。使用多目标优化，新的首选径向模型ek137已生成，可以很好地表示所有核心阶段的行程时间。绝热轮廓可以通过大多数外核得以维持，但与ak135模型一样，需要在底座上进行偏离。内芯剪切波速度的最新估计值包括在ek137中。