A vertical borehole geophone array

Abstract This note describes a vertical borehole geophone array which can be used in slim boreholes. The array was designed as part of a research program in Sweden to study the potential of seismic crosshole techniques for mapping cracks and fracture zones in crystalline rock. The design meets not only the constraints imposed by the slim boreholes (diameter 56 mm) available in Sweden for crosshole surveys, but also the desire to make array recordings with three component locked geophones. The use of vertical arrays in boreholes has been discussed by Galperin (1974).