Probing the Earth's Core

9506708 SONG This research is to model recordings of seismic waves travelling through the earth's core to recover its detailed structure. The inner core, from earlier work, is confirmed to be anisotropic, possessing a cylindrical symmetry around the earth spin axis with the N-S direction 3% faster in P-wave velocity than the E-W direction. The very top 60 km of the inner core appears not to be anisotropic with the interval from 60 to 150 km being a transition region. Several questions remain including the details of the anisotropy and the nature of the isotropic region near the inner core boundary. The theoretically possible, but undetected, phase PKJKP will be sought again in light of the new information on anisotropy. The answer to these questions bear on the nature of the earth's magnetic field, and the composition and physics of the core's material. ***