SEISMOLOGICAL EVIDENCE FOR DIFFERENTIAL ROTATION OF THE EARTHS INNER-CORE

The travel times of seismic waves that traverse the Earth's inner core show a small but systematic variation over the past three decades. Th is variation is best explained by a rotation of the inner core that mo ves the symmetry axis of its known seismic anisotropy. The inferred ro tation rate is on the order of 1 degrees per year faster than the dail y rotation of the mantle and crust.