The Representation of Seismic Displacements in Terms of Travelling Waves

The Poisson sum formula is used to transform the standing wave representation of seismic displacements in a radially stratified sphere into a travelling wave representation. The terms in the sum can be given a physical interpretation, via the method of stationary phase, as classical wave packets making successive traversals of the great circle through epicentre and receiver. The travelling wave representation forms the basis for the retrieval of structural parameters and source mechanisms from the spectra of travelling wave groups.