Ground vibration boom Ground vibration boom Ground vibration boom is a phenomenon of very large increase in ground vibrations generated by high-speed railway trains travelling at speeds higher than the velocity of Rayleigh surface waves in the supporting ground. This phenomenon, which is similar to a sonic boom from supersonic aircraft, was theoretically predicted in 1994. Its first experimental observation took place in 1997-1998 on the newly built high-speed railway line in Sweden (from Gothenburg to Malmo) for high-speed trains X 2000. At some locations along this line characterised by very soft ground (near Ledsgard) the Rayleigh wave velocity was as low as
Bomb hot gas. Under normal circumstances, this deflagration occurs too slowly to produce a significant pressure wave; low explosives, therefore, must generally be used in large quantities or confined in a container with a high burst pressure to be useful as a bomb. A high explosive bomb is one that employs a process called "detonation" to rapidly go from an initially high energy molecule to a very low energy molecule. Detonation is distinct from deflagration in that the chemical reaction propagates faster than the speed of sound (often many times faster) in an intense shock wave. Therefore, the pressure wave produced