Tomography of Seismic P-Waves from Earthquakes and Explosions(Part I Basic Concept and Theory)

Digital broad-band observations of seismic waves are becoming commonplace.They are replacing conventional observations,which have given only a partial picture of the wave field generated in the foci of seismic events.The new observations render rich-in some cases apparently complete-information on the wave field arriving at teleseismic distances.Broad-band recordings however are complex in appearance.They require a new approach to the analysis,if more detailed information about the focal process,and also about the structure of the intervening medium,is to be retrieved.Spectral seismograms are introduced as a means to recognize the morphology of the seismic signal,as arriving at the point of observation.On this basis details of the information can be recognized which would remain largely undiscovered in the conventional display of the wave field.