The Inner Core Translational Triplet and the Density Near Earth's Center

• Published in: Science (American Association for the Advancement of Science) Vol. 255; no. 5052; pp. 1678 - 1682
• Main Author: Smylie, D. E.
• Format: Journal Article
• Language: English
• Published: United States American Society for the Advancement of Science 27-03-1992; American Association for the Advancement of Science; The American Association for the Advancement of Science
• Subjects: Axial modes; Core; Core (Geology); Degrees of freedom; Density; Earth; Earth core; Gravimeters; Inner cores; Noise spectra; Outer cores; Parametric models; Research Article; Resonance; Rotation; Specific gravity; Spectral energy distribution
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.255.5052.1678

Four long records from superconducting gravimeters yield evidence of the triplet of translational oscillations of the solid inner core about its central position. Calculations of core oscillation modes allow identification of the three translational resonances at periods of 3.5820 ± 0.0008, 3.7677 ± 0.0006, and 4.015 ± 0.001 hours by their rotational splitting. Each resonance is defined by approximately 20 successive spectral estimates. A new Earth model brings the computed periods into agreement with observation. It has a central density of 12.960 grams per cubic centimeter, inner core radius of 1221.1 kilometers, and a density jump at the inner core boundary of 0.407 grams per cubic centimeter.