A theoretical and experimental comparison of three-dimensional seismic reflection and offset vertical seismic profiling (VSP)

Abstract

Diffraction tomography imaging has been applied to data acquired with two different measurement geometries at a buried waste disposal site. The experimental scale is quite small, having a horizontal extent on the order of 10 m and considering features at depths (most importantly, a layer of buried waste) of less than 10 m. Both a 3D reflection and a pseudo-3D offset vertical seismic profiling (VSP) geometry were used. The use of these two different geometries allows for a comparison of the results and limitations of each method. Images derived from both techniques must be interpreted with a knowledge of the theoretical resolution and limitations imposed by each measurement geometry and imaging algorithm. The reflection algorithm leads to images that contain hollow objects, a consequence of the reflection geometry and linearized theory; this algorithm is unable to image the sides of objects because of a lack of information at oblique reflection angles. Offset VSP experiences a blurring of objects along a line between the source and receiver because information is integrated over transmission raypaths. The two techniques provide images which are consistent with each other and the expectations based on theoretical considerations.