Accession Number : AD0800370

Title :   SIGNAL-TO-NOISE RATIO IMPROVEMENT BY TIME-SHIFTING AND SUMMING LASA SEISMOGRAMS.

Descriptive Note : Scientific rept.,

Corporate Author : TELEDYNE INDUSTRIES INC ALEXANDRIA VA EARTH SCIENCES DIV

Personal Author(s) : Chiburis, E. F. ; Hartenberger, R. A.

Report Date : 30 SEP 1966

Pagination or Media Count : 45

Abstract : Short-period LASA seismograms of nineteen earthquakes were prefiltered, time-shifted, and summed by digital computer to determine for each event the P-wave signal-to-noise ratio gain relative to the average input. Compared to the mean, the 'signal' amplitude, i.e., half the maximum peak-to-trough deflection in the P signature, was suppressed on each final trace about 3 db, whereas the root-mean-square level was lowered 18 to 21 db. The prefiltering and signal alignment procedures, however, significantly reduced the first-motion amplitude of unfiltered data. The average signal-to-noise ratio for each event was improved 15 to 18 db by summing all LASA traces. Approximately 5 db of the improvement is attributed to the modified time shifts resulting from the use of predetermined average travel-time anomalies. (Author)

Descriptors :   (*SEISMOMETERS, SIGNAL-TO-NOISE RATIO), MICROSEISMS, EARTHQUAKES, SEISMIC WAVES, UNDERGROUND EXPLOSIONS, DETECTION, NUCLEAR EXPLOSIONS, NETWORKS, NORTH AMERICA, SOUTH AMERICA, JAPAN, SOUND TRANSMISSION, TIME, DATA PROCESSING, NARROWBAND, BROADBAND, ELECTROMAGNETIC WAVE FILTERS, TABLES(DATA).

Subject Categories : Seismology
      Computer Systems
      Radiofrequency Wave Propagation

Distribution Statement : APPROVED FOR PUBLIC RELEASE