Ground shaking can result in both structural and nonstructural damage to buildings and other structures. It is commonly accepted that structural damage to modern engineered structures happens only in earthquakes larger than ML 5.0. The main parameters in structural damage is peak ground velocity (PGV). Ground shaking is usually measured as peak ground acceleration (PGA) in seismology and earthquake engineering. When PGA is greater than 18-34% of g (the force of gravity), moderate structural damage is possible, and very strong shaking can be perceived. In rare cases, nonstructural damage has been reported in earthquakes as small as ML 3.0. For critical facilities like dams and nuclear plants, it is crucial to ensure the ground shaking is not able to cause any unaffordable damages.