Differential PKiKP Travel Times and the Radius of the Inner Core

A value for the radius of the inner core is computed from differential PKiKP (PKiKP minus PcP) arrival time data and current Earth models. The data support an inner core radius of 1220–1230 km, the exact value depending on the model P velocity near the inner core boundary. For a model incorporating a decrease in the velocity gradient just above the boundary, in the transition zone of the core, the best value for the inner core radius is 1227.4±0.6 km. Comparison of pulse shapes and pulse durations for P, PcP, and PKiKP phases suggest that the core boundaries are sharp discontinuities relative to 1-s period waves. Complexity in explosion-related PKiKP signals is attributed to source effects.