Statics is the action of one body on another. A force is either a push or a pull. A force tends to move a body in the direction of its action. The action of a force is characterized by its magnitude, by the direction of its action, and by its point of application. Thus, force is a vector quantity, because its effect depends on the direction as well as on the magnitude of the action. Forces are classified as either contact or body forces. A contact force is produced by direct physical contact; an example is the force exerted on a
Moment magnitude scale it is based on, is not measured routinely for smaller quakes. For example, the United States Geological Survey does not use this scale for earthquakes with a magnitude of less than 3.5, which includes the great majority of quakes. Current practice in official earthquake reports is to adopt moment magnitude as the preferred magnitude, i.e., is the official magnitude reported whenever it can be computed. Because seismic moment (, the quantity needed to compute ) is not measured if the earthquake is too small, the reported magnitude for earthquakes smaller than is often Richter's . Popular press reports most often