SEISMIC SIGNAL ENHANCEMENT WITH THREE‐COMPONENT DETECTORS

The time‐averaged cross‐product of vertical and radial components of ground motion is multiplied by the original signal producing a function of ground motion in which rectilinearly polarized motion is enhanced. This provides some separation of seismic signals from noise when both occupy the same frequency and velocity bands. The vertical and radial motion is decomposed into its Fourier components, and the parameters of an equivalent ellipse are computed at each instant of time. The eccentricity, major axis, and angle of inclination of the ellipse provide criteria for identifying P and SV waves of different velocities.