This map displays selected epicenters for earthquakes that occurred between 1786 and 1987. Although accurate magnitude values have not been determined for many of the pre-instrumental earthquakes, it is believed that all of the earthquakes presented on this map have magnitudes of 5.0 or greater.

Symbols are plotted at epicentral locations, and symbol sizes are scaled into three magnitude categories. Within each category, duplicate epicenter locations have been eliminated. There are 2,351 separate epicenter locations, representing 2,480 earthquakes shown on this map. 

Because of recent increases in the number of quality of seisomgraph networks, the accuracy of epicentral parameters of earthquakes occurring since the mid-1960s is greater than that of earlier earthquakes. Earthquakes occurring since 1965 are distinguished on this map from earlier events by the intensity of color of the epicentral symbol, as indicated below. 

An extremely violent earthquake occurred north of Prince William Sound on Good Friday, March 27, 1964. This earthquake had a surface-wave magnitude of 8.4 and a moment magnitude of 9.2. The earthquake also generated a large sea wave (tsunami) which devastated many waterfront developments. The earthquake and its accompanying tsunami caused severe damage along Prince William Sound, Cook Inlet, and on the Kenai Peninsula. 

On the map, the epicenter of the 1964 earthquake is labeled with the date.