Short wavelength topography on the inner-core boundary

Aimin Cao , Yder J. Masson (1) , Barbara Romanowicz (2)

1 EPS - Department of Earth and Planetary Science [UC Berkeley]
2 Seismological Laboratory [Berkeley]

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

Domaines: Géophysique [physics.geo-ph]

Aimin Cao, Yder J. Masson, Barbara Romanowicz. Short wavelength topography on the inner-core boundary. Proceedings of the National Academy of Sciences of the United States of America, 2007, 104 (1), pp.31 - 35. ⟨10.1073/pnas.0609810104⟩. ⟨hal-01653919⟩