Studies of the Effect of Depth of Focus on Seismic Pulses: Estimation Procedure for Focal-Depth Determination of Seismic Disturbances

Abstract

A new data processing technique is suggested to estimate the delay time between initially uptraveling energy which is reflected once at the earth's surface and initially downtraveiing energy on earthquake seismograms. The method uses optimum inverse filter together with a criterion that measures the simplicity of a seismic signal convolved with an inverse filter. The inverse filters are designed to extract primary energy in the presence of surface reflected energy and random noise on the basis of a least-mean-square error criterion. Filter design Is dependent on the delay time between primaries and surface reflected events, their amplitude ratio and noise to signal power ratio. The simplicity criterion was devised on the assumption that a maximum in the concentration of normalized seismic signal energy above a minimum level indicates which filter was most correctly designed. This is visualized as an expression of the hypothesis that the primary seismogram is generated by a few large discontinuities, rather than by many minor boundaries.The technique was applied to band-limited synthetic signals that contained several primary-secondary pairs in the presence of random noise. Of 27 synthetic signals which were analyzed, the procedure successfully selected the correct delay time in 22 cases,

Studies of the Effect of Depth of Focus on Seismic Pulses

“…4 by G. Leblanc (1966) discusses the spectra of a real earthquake in detail. This problem has also been discussed by Nakamura (1963B) C Merdler (1964).…”