Earthquake Characteristics and Earthquake-Explosion Discrimination

Theoretical seismograms enable the amplitude and waveform of body waves to be incorporated as constraints in an inversion scheme for an earth model or the source time function of an earthquake or explosion. The lower mantle has long been known from travel time studies to be nearly laterally homogeneous and to have elastic moduli and density gradients that vary smoothly and slowly over large ranges of depth. Consequently, in the distance range 40-80 degrees simple geometric ray theory that includes surface reflections combined with a simple source description is sufficient to synthesize the observed waveform of body waves Herrmann, 1975. At shorter distances, however, geometric ray theory must be abandoned in favor of a full wave theory that includes non-ray theoretical effects of waves grazing regions in the upper mantle and crust having discontinuous andor rapid variations in velocity and density. Author