Seismic tests are conducted during the CPT or CPTU investigation (SCPT or SCPTU). SCPTU probings involve the measurement of transverse wave propagation time in the soil between the terrain surface and the probe tip, in which additional accelerometers are installed. A seismic wave is generated by the impact (in the horizontal direction – a transverse, shearing wave) against the steel element placed in the soil on the terrain surface. At the time of impact, signal (speed or acceleration) record starts in the probe tip. On the basis of the seismic wave reaching time on the depth, at which the probe is currently, the average velocity of the transverse wave propagation in the soil (Vs) is specified. While executing investigation, for example, every 1 m deep and comparing the results of measurements on adjacent levels with each other, the velocity of wave propagation in a given layer with a thickness of 1 m can be specified.

Measurement components of the seismic system can be permanently embedded in a CPTU cone or attached to it as a separate wire section. Such a System can be equipped with a single accelerometer, set in the horizontal plane (in one direction) or with a set of three accelerometers, which allows to measure, regardless of the direction, the force in the horizontal plane, and, in addition, to measure the velocity of longitudinal wave propagation (Vp) and to set deformation module (E0) and Poisson’s ratio (v).