Abstract The Earth's Inner Core may rotate at a different speed than Earth's crust–mantle. We use observations for antipodal earthquake and station pairs to examine the arrival time shift of the whispering-gallery wave which propagates tangentially along the top of the Inner Core. Observations of these waves for earthquakes which occurred at the same location reveal that travel times vary by ≥0.2 s over the past 20 years. We propose that these time shifts are caused by the interaction of a zero rigidity patch (lateral heterogeneity) at the Inner Core surface with the Inner Core differential rotation. The simplest interpretation infers a rotation rate of 0.05°/year, which is one order of magnitude smaller than those reported by previous studies. Our result may also give constraint to the provenance of a zero rigidity patch at the Inner Core surface. The Fresnel zone coverage of whispering-gallery PKIIKP+… antipodal measurements beneath the Inner Core boundary extend over ~60% of the boundary surface, in contrast to PKiKP–PKP paths which individually measure specular reflections (~1 Hz) from the top of the ICB over Fresnel zones each encompassing 0.002% of the Inner–Outer Core boundary.

中文翻译：

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从对映地震观测推断出的内核差旋转

摘要 地球内核的自转速度可能与地壳-地幔的速度不同。我们使用对映地震和台站对的观测来检查沿内核顶部切向传播的回音壁波的到达时间偏移。对发生在同一地点的地震的这些波的观测表明，在过去 20 年中，旅行时间变化≥0.2 s。我们提出这些时间偏移是由内核表面的零刚度补丁（横向异质性）与内核微分旋转的相互作用引起的。最简单的解释推断自转率为 0.05°/年，这比之前研究报告的数据小一个数量级。我们的结果也可能限制内核表面零刚度补丁的来源。内核边界下的回音壁 PKIIKP+... 对映测量的菲涅耳区覆盖范围扩展到约 60% 的边界表面，与单独测量来自 ICB 顶部的镜面反射 (~1 Hz) 的 PKiKP-PKP 路径相反在菲涅耳区域上，每个区域都包含 0.002% 的内-外核边界。