Asymptotic structure in torsional free oscillation data for the Earth

Abstract

THE eigenfrequencies, _nσ_l of the torsional modes, _nT_l, of a spherically symmetrical, nonrotating, elastic, isotropic Earth model, are defined, for fixed wave number k=(l+ 1/ 2 )/a, by the eigenvalue problem (where U=U(r); μ = μ(r); ρ = ρ(r); a ≤ r ≤ b) and by the (zero stress) boundary conditions where μ, denotes rigidity, ρ density, a the radius of the core and b the radius of the Earth¹.