Earthquake Ground-Motion Amplification in Southern California

The two most important factors influencing the level of earthquake ground motion at a site are the magnitude and distance of the earthquake. The map available here shows the influence of a third important factor, the site effect: conditions at a particular location can increase (amplify) or decrease the level of shaking that is otherwise expected for a given magnitude and distance. Combining information about site effects with where and how often earthquakes of various magnitudes are likely to occur should provide improved assessments of seismic hazard. [Summary provided by the USGS.]