Design of an Ocean Bottom Seismometer with Response from 25 Hz to 100 Seconds1

A new ocean bottom seismometer for seismicity study, evaluation of seismic hazard, and for collection of refraction data has been designed. The basic system contains a feedback controlled long-period vertical seismometer, a short-period vertical seismometer and a pressure-compensated crystal hydrophone. The long-period seismometer response models a standard 15 second long-period suspension - 100 second galvanometer combination allowing study of long-period phenomena never before recorded on a free-fall/ pop-up ocean bottom seismometer. The entire system is under the control of a cosmos microprocessor. The microprocessor produces modified IRIG time code and such housekeeping functions as delayed turn on; cage, uncage and centering for the long-period suspension; in situ calibration and timed ballast release. The ocean bottom seismometer also includes an acoustic transponder for location, navigation and release.