A PROGRAM FOR ROUTINE LOCATION OF T-PHASE SOURCES IN THE PACIFIC

Abstract
Data for this program is supplied principally by the Pacific Missile Range hydrophone network. Hydrophone records are forwarded weekly for reading at Honolulu. In correlating arrivals records from all stations are viewed together. Correlation is established by similarity in shape and level and by locations determined roughly from arrival time differences. Arrival times and power levels are read for processing by an IBM 7040 computer. The solution for location and origin time is the leastsquares fit to all hydrophone arrivals which are weighted according to their distribution in azimuth and their distance from the T-phase source. The iterative solution proceeds on the assumption of zero parallax and flat earth in the vicinity of the source. Velocity is derived from shot calibrations and from averaging across a contour map of local velocity. For the computer program this is expressed as a power series in latitude and longitude for each station and for each quadrant of the Pacific. A T-phase strength is computed from readings of peak power level. This strength is computed for a distance of thirty degrees from the source. The lower half and the upper quarter of all hydrophone readings are arbitrarily rejected from computation of strength as being influenced by topographic shadowing or containing mistakes. Events which can be correlated at four or more hydrophones occur at an average rate of about one per hour.

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