In 1953, Richard Jolly used geophones coupled to the borehole wall to record seismic waves in the subsurface, and he highlighted the interpretive benefits of downhole recording. In the western world, the coupled downhole geophone was a first of its kind and was the ancestor to modern receiver tools (Figure 1) used in the vertical seismic profiling (VSP) method. The translation, by SEG, of Gal'perin's 1974 book on VSP from Russian into English increased awareness of the progress in borehole seismology made in Russia; the case studies outlined in the book gave further prominence to the benefits of the VSP method. Zero-offset VSP (meaning the source is relatively close to the borehole to provide 1D information) or ZVSP is now an essential part of the interpreter's toolkit that gives a seismic time-to-depth relationship, in-situ elastic properties, and multiple-reduced reflectivity. ZVSP continues to provide a key link between surface seismic images and geologic properties. In addition, Q measurement and the identification of multiple-generating and mode-changing horizons from near-offset VSP provide further interpretive insights. In-situ velocities also assist with building velocity models for migration and inversion.

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