The data shown on this map and listed in table 1 are for earthquakes that were originally included in a study of seismic risk in the United States (Algermissen, 1969). This data file has been recompiled and updated through 1980. Some revisions of epicenters and intensities in the original file have been made, and intensities have been assigned to earthquakes that previouly had none assigned. Only earthquakes that had epicenters within the boundary of the State are listed in table 2, even though earthquakes that had epicenters in bordering states or countries may have been felt or may have caused damage in the State. Intensity values were updated from data sources that were not available at the time of original compilation. Some epicenters were relocated on the basis of new information. The data shown in table 1 represent best estimates of the epicenter, magnitude, and intensity of each earthquake on the basis of historical and current informaiton. Some of the aftershocks from large earthquakes are listed, but not all, especially for the earthquakes that occurred before seismic instruments were universally used.
