Accession Number : AD0872607

Title :   Investigation of P Travel Time-Curve.

Descriptive Note : Seismic data lab rept.,

Corporate Author : TELEDYNE INDUSTRIES INC ALEXANDRIA VA EARTH SCIENCES DIV

Personal Author(s) : Evernden, J. F. ; Clark, D. M.

Report Date : 29 JUL 1969

Pagination or Media Count : 93

Abstract : By using a large number of LRSM stations and a number of earthquakes from all azimuths and the well controlled nuclear explosions, a study of the 'P' travel-time curve reveals it to be nearly a series of straight-lines or legs throughout the total distance of about 105 degrees. Time as well as amplitude residuals were determined for the stations used and were found to be acceptably consistent. Analysis of the variance of the several modes of handling the data of each leg is shown which is significant in indicating the relative probability of each model as an explanation of the observed data. The 'F' statistic value, degrees of freedom, etc. are shown for each leg. The existence of real differences in 'P' travel-times and thus of mantle velocity structure are illustrated indicating that the velocity varies as a function of azimuth. The very close correlation between site geology and average noise level on signal amplitude is discussed as well as this effect on magnitude calculations. In addition, a computed 'B-factor' curve developed from this study is compared with Gutenberg's and one by Clawson of Geotech. (Author)

Descriptors :   (*SEISMOLOGICAL STATIONS, NOISE), (*SEISMIC WAVES, VELOCITY), (*UNDERGROUND EXPLOSIONS, DETECTION), NUCLEAR EXPLOSIONS, SEISMOMETERS, MATHEMATICAL MODELS, POWER SPECTRA, EARTHQUAKES, PHASED ARRAYS, NETWORKS, CORRELATION TECHNIQUES, ANOMALIES.

Subject Categories : Seismology
      Seismic Detection and Detectors

Distribution Statement : APPROVED FOR PUBLIC RELEASE