Lg-Wave Propagation in Heterogeneous Media
Abstract
The Lg wave phase which is of considerable interest for nuclear discrimination problems is normally observed after propagation through considerable distances. This phase is dominantly guided in the crustal waveguide, which is known to be a region with very considerable horizontal variability in properties. The effect of heterogeneous crustal structures on Lg waves has been determined by using a 'coupled-mode' technique in which the local seismic wavefield in the real medium is expressed as a combination of the modal eigenfunctions of a stratified reference structure. Departures of the seismic properties in the medium from those of the reference medium lead to coupling between the amplitude coefficients in the modal expansion. The evolution of these modal weighting factors with horizontal position are described by a coupled set of ordinary differential equations. This approach provides a calculation scheme for studying guided wave propagation over extended distances, at frequencies of 1 Hz and above. The heterogeneity models which have been used are two-dimensional and calculations are carried out for one frequency at a time.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 06, 1988
- Accession Number
- ADA198920
Entities
People
- Brian L. Kennett
Organizations
- Australian National University