Two Searches for Observational Evidence of Inner Core Rotation

这个项目将开发和应用两种地震学方法来改进对地心相对于固体地球其余部分的旋转速率的估计。首先，研究人员应在相关的源区域寻找重态，以便能够非常精确地测量指示内核旋转的差分旅行时间。(双重地震，是在不同时间发生但几乎完全相同地点的一对地震。差分传播时间是同一地震记录上两个信号之间的时间。其次，他们应寻找从震源（地震或核爆炸）到对跖点几乎垂直在地球上传播的地震波的传播时间变化的迹象。通过研究已经深入到内核深处的地震波的例子，因此对内核的各向异性和非均质性的影响更加敏感，研究人员将能够更好地理解引起走时变化的基本机制。

RichardsEAR-0125691This project will develop and apply two seismological methods for improving estimates of the inner core's rate of rotation with respect to the rest of the solid Earth. First, the investigators shall search for doublets in pertinent source regions, to enable very precise measurement of differential travel times that are indicative of inner core rotation. (A doublet, is a pair of earthquakes occurring at different times but in almost exactly the same location. A differential travel time is the time between two signals on the same seismogram.) Second, they shall search for indications of travel time change in seismic waves that have traveled almost vertically in the Earth, from a seismic source (an earthquake, or a nuclear explosion) to its antipode. By working with examples of seismic waves that have passed very deeply into the inner core, and are thus more sensitive to effects of anisotropy and inhomogeneity in the inner core, the investigators will be better able to understand the basic mechanism causing travel time changes.