Short wavelength topography on the inner-core boundary

• Published in: Proceedings of the National Academy of Sciences
• Main Authors: Cao, Aimin, Masson, Yder J., Romanowicz, Barbara
• Other Authors: Department of Earth and Planetary Science UC Berkeley (EPS), University of California Berkeley (UC Berkeley), University of California (UC)-University of California (UC), Seismological Laboratory Berkeley
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2007
• Subjects: [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]; Sandwich Islands; South Sandwich Islands; Yellowknife
• Online Access: https://hal.archives-ouvertes.fr/hal-01653919; https://hal.archives-ouvertes.fr/hal-01653919/document; https://hal.archives-ouvertes.fr/hal-01653919/file/cao_pnas07.pdf; https://doi.org/10.1073/pnas.0609810104

International audience Constraining the topography of the ICB is important for studies of core-mantle coupling and the generation of the geodynamo. We present evidence for significant temporal variability in the amplitude of the inner core reflected phase PKiKP for an exceptionally high quality earthquake doublet, observed post-critically at the short period Yellowknife seismic array (YK), which occurred in the South Sandwich Islands within a ten year interval (1993/2003). This observation, complemented by data from several other dou-blets, indicates the presence of topography at the inner-core boundary, with a horizontal wavelength on the order of 10 km. Such topography could be sustained by small scale convection at the top of the inner core, and is compatible with a rate of super-rotation of the inner core of ∼0.1-0.15 deg/year. In the absence of inner core rotation, decadal scale temporal changes in the ICB topography would provide an upper bound on the viscosity at the top of the inner core. Inner Core | Topography | PKiKP | Super Rotation