- GeoRef, Copyright 2005, American Geological Institute. Reference includes data supplied by Society of Exploration Geophysicists, Tulsa, OK, United States
A system of recording and reproducing exploration seismograms on magnetic tape is described. Geophones and amplifiers with broad-band response, approximately 4-300 cps, are used to channel the seismic signals to a 13-track tape recorder. The magnetic tape is 1 inch wide. One of the tracks is used to record a time reference signal. Each broad-band recording is formed into an endless loop and played back in repeating fashion. The signals are fed through a flexible system of filtering and mixing, then examined on the screen of a 12-trace cathode-ray oscilloscope. The sweep of the oscilloscope is synchronized with the loop and, by varying the sweep speed, the entire record, or an expanded portion thereof, is held stationary on the screen. Conventional paper records of the modified record as reproduced on the screen are finally made with a regular seismic camera. Played-back records with variations of filtering and mixing are shown in order to illustrate the potential usefulness of the technique.