Slow-speed Tape Recordings of Seismic Signals

Abstract

SEISMIC interpretation at the University of Tasmania has been enhanced by using very-low-speed magnetic tape recordings in conjunction with the normal pen recordings. When played back with a time compression of 250, the outputs from the short period ‘Willmore’ seismometers become audible. By comparing the tape and the pen recordings for earthquakes easily identifiable on the pen recordings it has been found, once the various tones are memorized, that it is not only possible to hear seismic activity which is lost in background noise on the pen records, but also to tell approximately the region from which they originated. Since a 2,400 ft. reel of 0.25 in. magnetic tape lasts approximately 3 months if used continuously, this slow-speed recording also affords an economical way of permanently storing the records in an electrical form.