The map above is an earthquake epicenter map for the Pacific Northwest portion of the United States. (An epicenter is the location on earth's surface that is directly above the source of an earthquake.) This map shows the epicenters of earthquakes that occurred in the two weeks prior to July 11th, 2004. The color of each square corresponds to the time of the earthquake and the size of the squares corresponds to the strength of the earthquake.
The map was produced by the Pacific Northwest Seismographic Network. Their website displays a continuously updated version of this map. Full USA earthquake mapping can be found at the USGS Earthquake Hazards Program website.