ESTIMATION OF NEAR-SURFACE ELASTIC PARAMETERS USING MULTICOMPONENT SEISMIC DATA

In multicomponent seismic reflection surveys, surface and near-surface effects can severely deteriorate the quality of reflection data. Such effects are more pronounced on shear-wave than on compressional-wave profiles. Amplitude anomalies, statics, and strong coherent source-gen erated noise (i.e., surface waves) are often associated with inhomogen eous, poorly compacted near-surface sediments of the weathering layer. The magnitude of such effects, increases when sources and receivers a re deployed at or near the surface in proximity to such inhomogeneitie s. Near-surface effects can be investigated with respect to their dept h of occurrence by burying seismic sources and/or receivers at various depths below the inhomogeneous weathering layer. In this context, an experiment was conducted to collect multicomponent seismic field data on a borehole-controlled test site in east Texas. Data were recorded o n three-component. surface and buried receivers using a full-vector wa ve-field surface source. Although the geology appears simple, results of modeling one or two components of the field data with synthetics yi elds nonunique estimates of elastic parameters. Effects of anisotropy and heterogeneities are better identified and estimated with full-wave field surface and buried receiver observations. Single fold data from buried receivers yield reflection events with higher signal-to-noise r atio than 30-fold CDP surface data previously acquired in the same are a.