A Japanese company, OYO Corporation, created the PS-suspension probe for recording P-Wave and S-Wave velocity data in geomaterials using one borehole back in the 1980’s. A recent update to the probe has made it digital.
The probe is most frequently used in the off-shore oil and gas industry but has also been used on a limited basis in the US, most notably on several high-profile San Francisco Bay-area bridges. It has the capability of logging this data up to a depth of 500-m in an un-cased open, water-filled borehole. More info at New Civil Engineer.