A crosshole test aims in general at the determination of shear modulus and Young’s modulus calculated based on S- and P-wave velocity. Therefore a strong S-wave borehole source is needed. (P-waves are generated as a side effect of the s-wave excitation.)
The borehole receiver should contain directional sensors oriented horizontally and vertically (at least a triaxial sensor array is needed). This is essential for a proper distinction between P- and S-waves. Since only horizontal ray paths are considered a single (but multi-directional) receiver is sufficient. The receiver needs to be mechanically coupled to borehole wall to enable the transfer of the S-wave component.
Geotomographie recommends the new Borehole Impacter Source BIS as a SH-wave source. A borehole geophone BGK 3, BGK 5 or BGK 7 equipped with a pneumatical clamping device should serve as receiver.
In case of dry boreholes with depths smaller than 30 m the SV Borehole Hammer is a low-priced alternative. However, the generated seismic energy is much lower than generated by the Borehole Impacter Source BIS.
