Inner core structure - probing the African hemisphere boundary

The inner core is Earth's deepest region and many of its properties still remain elusive - the exact composition of the iron-nickel alloy of which is it formed, the crystalline phase or phases present and its age and dynamical history. One of the more mysterious properties of the inner core is the presence of a seismologically observable hemispherical structure in the inner core, which persists through at least half if its depth. Hemispherical inner core structure requires that there be parts of the inner core where either a gradual or rapid transition between the two hemispheres takes place. A sharp boundary has been observed in the uppermost 100km of the inner core; here I investigate the nature of the boundary under Africa. By using PKPbc-PKPdf differential travel times, I am able to seismologically image the nature of the hemisphere boundary region under Africa. Core sensitive waves generated by earthquakes in the Americas, the polar regions, Asia and the Indian Ocean are used to discern the perturbations to PKPdf travel times though the inner core. The PKPdf waves used sample the inner core under Africa with a range of ray angles, permitting the investigation of the variations present in both anisotropic and isotropic P-wave velocity in the inner core. The PKPdf waves are sensitive to the upper 360km of the inner core, allowing us to image a region which could have been growing for hundreds of millions of years. A stronger understanding of the seismological properties of the inner core will help us to better distinguish between possible mechanisms for the formation of both hemispherical structure and anisotropic texture in the inner core.