The States and the U.S. territories are affected every year by recurring natural hazards. Earthquakes, although they happen infrequently in comparison with floods and hurricanes, are dangerous because of their unpredictability. Damaging earthquakes occur most frequently in California and Alaska, but some of the largest have struck in the Eastern United States. Secondary losses caused by fire, flooding from dam failure or tsunamis, and aftershocks can be as great as the primary losses from the main shock. To reduce the risk from recurring natural hazards, the USGS integrates scientific knowledge on hazards with planning and engineering data on location, exposure, and vulnerability to foster prevention, mitigation, and prepare local jurisdictions.
Floods happen more frequently than any other natural hazard.
The States and the territories have communities that are at risk from flooding that occurs annually and in every season of the year primarily as riverine and flash floods caused by thunderstorms, rapid melting of ice and snow, storm surges, and tsunami flood waves. Flash floods cause greater loss of life than riverine floods because the technology to forecast them is not fully developed, but riverine floods in the more than 6 million miles of the Nation's river systems cause the highest economic losses. Storm surges generated by hurricanes in late summer and autumn have inundated thousands of miles of the coastlines of the Gulf of Mexico and the Atlantic Ocean. Urbanization, deforestation, wildfires, and other human and natural actions that alter natural drainage patterns keep increasing the vulnerability of communities to flooding. Volcanic eruptions are restricted to Hawaii and the Western United States.