Evidence for inner core super-rotation from time-dependent differential PKP traveltimes observed at Beijing Seismic Network

• Main Authors: Xiaoxia Xu, Xiaodong Song
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Sandwich Islands; South Sandwich Islands
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.210.8362; http://www.geology.illinois.edu/people/xsong/Sites/papers/xusong03_gji.pdf

In an effort to confirm and constrain inner core rotation, we examine earthquakes from the South Sandwich Islands recorded at the Beijing Seismic Network. We obtained a total of 109 high-quality measurements of PKP(BC)-PKP(DF) differential traveltimes by waveform cross-correlations from earthquakes spanning over 30 years. The results show robust temporal changes in PKP(BC)-PKP(DF) residuals along this pathway, providing new support for the differential inner core hypothesis. We also observed evidence for a lateral velocity gradient in this part of the inner core. Assuming that the temporal changes result from a shift of a lateral structure due to an inner core rotation, we estimate the inner core rotation rate to be about 0.41 ± 0.12 ◦ yr−1 faster than the mantle. Key words: Beijing Seismic Network, inner core rotation, PKP.