[S18-1] Inner core structure and dynamics

[S18-1-03] Temporal change of seismic data associated with the Earth's inner core: inner core super-rotation or temporal change of inner core surface?

^○Lianxing Wen^{1, 2}, Jiaoyuan Yao² (1.Stony Brook University, 2.University of Science and Technology of China)

Seismic evidence has shown that seismic compressional waves that are refracted (PKIKP) and reflected (PKiKP) off the inner core exhibit temporal changes. Two explanations have been put forward to account for the observed temporal change of the seismic data: inner core super-rotation and temporal change of inner core surface. In this presentation, we present observations of temporal change of seismic data based on global earthquake doublets found in the last 20 years and discuss the plausibility of their interpretations in the context of inner core super-rotation and temporal change of inner core surface. We show that inner core super-rotation is not required by the seismic data, cannot consistently explain the seismic data sampling different regions of the inner core and fail to track the presumed seismic scatterers appeared between some time intervals of the doublets, while temporal change of inner core surface can explain all the seismic data without requirement of inner core differential rotation. Accordingly, we present a global map of temporal change of inner core surface in the last 20 years, and discuss its implications to thermocompositional conditions near the inner core surface and driven forces of geodynamo.