HR: 0800h
AN: S31B-1067    [Abstracts]
TI: A new method of normal mode calculation
AU: * Kobayashi, N
EM: shibata@geo.titech.ac.jp
AF: Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8551 Japan
AB: Numerical method of calculating normal modes of the Earth is classical problem in seismology and many methods have been developed, e.g. MINEOS, OBANI (Woodhouse 1989) and DISPER80 (Saito 1989). These methods are based on direct numerical integration of the governing differential equations (Runge-Kutta method). The methods are efficient for search for (real) eigenvalues of non dissipative cases but have some trouble to seek complex eigenvalues of dissipative or leaky oscillations. On the other hand, in solar seismology, the Henyey type relaxation method is used to calculate acoustic and gravity modes of the sun and stars (e.g. Unno et al. 1989). The latter method is generally more stable for eigenvalue problems of a self-gravitating gaseous body where the density and pressure vary exponentially near its surface. The efficiency of the method is, however, depends on initial guess of eigenvalues and eigenfunctions. Here we propose a new method to overcome the deficiency of the above methods. This method is formulated with the aid of the concept of the Henyey type relaxation method but does not needs initial guess of eigenfuctions and solves the problem more directly like the Runge-Hutta method. Some mumerical tests show good convergence of complex eigenvalues in our method. So the proposed method is effective to calculate solid modes, acoustic and gravity modes and ocean modes interfered with the other parts of the earth and planets.
DE: 7255 Surface waves and free oscillations
DE: 7260 Theory and modeling
DE: 7200 SEISMOLOGY
SC: Seismology [S]
MN: 2004 AGU Fall Meeting