THE INFLUENCE OF A DENSITY STRATIFICATION AND OF AN INCOMPRESSIBILITYMODULUS ON THE SPECTRUM OF CORE MODES

The concept of a deformation of a simple, non-rotating, spherically sy mmetric earth model with a fluid outer core, although it is a highly a rtificial physical situation, provides a useful computational algorith m that allows one to determine analytically modes of vibration without any Love-number theory. In particular, on these analytically determin ed modes, we impose regularity conditions at the centre and boundary c onditions at the surface, as well as conditions of continuity at the i nner-core-outer-core boundary and at the core-mantle boundary. They le ad to an eigenvalue equation for the frequency of oscillation. The ran ge of frequencies obtained in this way for different earth models give s an indication of the influence of compressibility and non-homogeneit y on the spectrum of eigenfrequencies.