ABSTRACT
Many people are of the opinion that the greatest earthquake losses in terms of life and property are attributable to permanent crustal displacements along faults, but ground shaking has been, and will continue to be, the primary seismic hazard. Property losses from earthquake-induced ground shaking are estimated to be far greater than losses from any other geologic hazard for the period from 1970 to 2000. For shallow-focus earthquakes, there is a direct relation between magnitude and the intensity of ground shaking. However, because of a complex assemblage of variables, it is difficult to assign a magnitude threshold that is responsible for potentially damaging ground motions. Induced hazards normally accompany larger earthquakes, but their types and impact are highly variable. For many historical earthquakes, certain induced hazards have been responsible for catastrophic casualty and/or property losses. Such earthquakes are often remembered, not for their primary, but for their induced effects.
