New normal mode constraints on bulk inner core velocities and density

Publication date: Available online 6 September 2019Source: Physics of the Earth and Planetary InteriorsAuthor(s): Alexander J.S. Robson, Barbara RomanowiczAbstractInner core elastic parameters Vp, Vs and density (ρ) inform both experimental and theoretical studies of inner core composition and potential light element candidates. Meanwhile, constraints on the density jump at the inner core boundary offer much-needed observational insight into the processes powering the geodynamo. Thus, obtaining accurate observational constraints on the elastic structure of the inner core is key to gaining better understanding of its composition and dynamics.While body wave phases provide information on inner core P velocity and anisotropy structure, constraining shear velocity and density currently relies predominantly on core-sensitive normal mode observations. Since the construction of the Preliminary Reference Earth Model (Dziewonski and Anderson, 1981), which was largely based on such data, the database of observed normal modes has become both larger and more accurate, and new model exploration methodologies have become computationally feasible.Here we use recent normal mode center-frequency catalogues to simultaneously explore average shear (Vs) and compressional (Vp) velocities, as well as density (ρ), in the inner core via a Monte Carlo parameter-space search.We find best-fitting Vp values (11,160–11,180 m/s) in good agreement with PREM, while Vs values (3560–3590 m/s) favor ...
Source: Physics of the Earth and Planetary Interiors - Category: Physics Source Type: research