First-arrival Seismic Holograms.
4th Int'l Symp Acoustical Holography Santa Barbara California 4/72 Plenum Pub Corp Pp 381-400 :381-400
Under certain conditions, phase-only impulse seismic holograms of underground objects may be made by using only the source-object- detector travel times to calculate the relative phases of the arriving signals. This circumstance eliminates the necessity of recording and processing entire signals and, in principle, allows one to make seismic holograms by resorting to simple and repid timing circuitry, rather than the comparatively complex apparatus needed to record and digitize entire signals. By eliminating such noise contributions as shear and surface waves the technique of first-arrival seismic holography also results in a large improvement in the signal-to-noise ratio of the recorded fringe data. A comparison of first-arrival seismic holograms made with actual field data and holograms made with entire signals from the same field data shows that the first-arrival holograms (and their reconstructions) are superior to those made with the full seismic records.
4th Int'l. Symp. Acoustical Holography, Santa Barbara, California, 4/72, Plenum Pub. Corp., Pp 381-400