THE CROSSWISE SUM METHOD FOR MAXIMUM-LIKELIHOOD FILTERING OF LASA SEISMOGRAMS.
TELEDYNE INDUSTRIES INC ALEXANDRIA VA EARTH SCIENCES DIV
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The two earthquakes reported earlier, 10 November 2965 and 25 November 1965, were processed and analyzed using the crosswise sums method. With this method we first form 25 traces, each the phased sum of 21 prefiltered subarray traces, one from each subarray and then maximum-likelihood filter the set. The final outputs from the maximum-likelihood filter are 1.5 to 4 db down in signal-to-noise ratio from the phased sum of all of LASA. The signals are remarkably similar on these 25 crosswise sum traces so much that the symmetrical maximum-likelihood filter introduced no precursor. Author