During the 1989 Loma Prieta earthquake, the hydraulic fill densified by vibro compaction at Emeryville on Treasure Island and Bay Farm Island in California in the United States did not liquefy (Seed et al., 1990). However, some untreated areas close to the treated areas had excessive settlement, lateral spreading, and sand boils. This case history demonstrates the effectiveness of vibro-compaction in mitigating liquefaction of cohesionless soil. In addition to vibro-flotation, there are other types of equipment used for vibro-compaction. Vibro-flotation has a vibrator at the bottom of the probe (also called bottom vibrator), which generates vibration by the rotation of an eccentric weight at the bottom of the probe. Other types of equipment have a vibrator or hammer on the top of the probe (also called top vibrator) (Han, 2015).
However, the key difference is that vibro compaction relies on the densified in situ soils, while deep replacement (Vibro stone columns) relies on using columns together with the surrounding soil to form a composite foundation (Han, 2015).