The Parallel Seismic test was developed for checking the integrity and length of piles in this situation. The method consists of installing a closed end tube adjacent to and deeper than the pile or structure under test. A piezo electric probe is used to measure the transit time of a shock wave traveling through the pile, as it is raised in 50cm vertical steps.

A change in the rate of signal arrival time increase with depth indicates either the pile toe or a discontinuity in the shaft.