When a vertical seismic profile (VSP) is recorded, the illuminated part of a reflector depends upon the shape and position of the reflector itself as well as on the seismic velocities and the positions of sources and receivers. A preferable arrangement for the investigation of structures of reflectors is to fix the receiver(s) at constant depth(s) in the well and move the source horizontally along a line at the Earth's surface, usually called a 'multioffset VSP' (MSP) or 'walkaway VSP.'As a test of the resolution power of this survey geometry, synthetic records were generated from a subsurface model by inverse Kirchhoff migration. Three different methods were applied for the reconstruction.Wavefront construction leads to the correct shape of the reflectors, thus assuring the validity of the modeling method applied. Reflection-point mapping delivered a near similarity to the model, but without focusing fault edges. Kirchhoff migration resulted in a detailed image of the reflectors with fault edges focused.Application of reflection-point mapping and Kirchhoff migration to a real survey delivered results consistent with results from a survey at the Earth's surface.

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