Source-generated noise on multicomponent records

Susan L. M. Miller, Malcolm B. Bertram, Donald C. Lawton

An examination of shot records from a multicomponent seismic reflection survey showed that the converted-wave bandwidth overlapped with the surface-wave bandwidth. Rayleigh-wave energy was 2 to 3 times higher on the radial channel than on the vertical channel. The single-point receiver vertical records displayed more surface-wave noise than equivalent records obtained using conventional geophones in arrays. After bandpass filtering, noise levels on both records were comparable. Far-offset multicomponent records showed less surface-wave contamination than near-offset shots, but reflection signal was masked by multiple-refraction energy on both components. Geophones were effective at separating components so that reflection signal was retained even when there was higher amplitude noise in the orthogonal direction. P-P and P-SV reflection amplitudes were approximately equivalent at outer offsets but could not be measured at near offsets due to noise contamination. At near offsets, the A/D resolution of the recording instruments was insufficient to recover converted-wave signal from beneath high-amplitude surface-wave and headwave energy.