Solidity of the Inner Core of the Earth inferred from Normal Mode Observations

SOLIDITY of the inner core was originally inferred on the basis of the assumption that the inner core has the same composition as the surrounding material of the outer core¹. If, however, the observed increase in compressional velocity is related to a compositional change or, as suggested by Elsasser and Isenberg², to a new phase of iron with rearranged electronic orbits, then the inner core might be liquid³. It was believed that conclusive evidence of solidity of the inner core would come from observations of body waves of the type PKJKP, SKJKS or SKJKP, phases that travel through the inner core as a shear wave. But no reliable observations of these phases have been reported so far.