The excitation of normal modes of the Earth by sources with volume change

A formulation is given for the normal mode excitation by a collapsing cavity, including as special cases the tangential, normal and point dislocation. The results are compared with corresponding results for a phase transformation. In dislocations with volume change, the action of static pressure modifies the traditional expression for the excitation, but under certain’ conditions the effect is shown to be of minor importance to the observable normal-mode spectrum.