Source‐Depth Determinations using Spectral, Pseudo‐Autocorrelation and Cepstral Analysis

Abstract

Interference between P and pP (or Pn and pPn) in a seismic signal causes the spectrum of the combined wave train to be scalloped with a period equal to the depth‐phase delay time τ. Determination of the null frequency interval (Δf= 1/τ), together with a knowledge of the overburden compressional velocity, permits an estimate of the source depth to be made. Scalloping produced by reverberations at the recording station can be reduced by forming the average of a suite of individual station spectra. The spectral bandwidth available for analysis can be broadened by removing instrument response. To determine objectively the periodicities in the average spectrum, the cepstrum and pseudo‐autocorrelation are computed. This depth determination method combining spectral, pseudo‐autocorrelation, and cepstral analysis is applied successfully to Pn or P data sets for three underground explosions whose depths are known a priori. Copyright © 1970, Wiley Blackwell. All rights reserved