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The map above is an earthquake hazard map for
the United States. Two factors were considered in
making this map: 1) the frequency of earthquakes in
different parts of the United States, and 2) how far
ground shaking extends from an earthquake source (related
to earthquake strength and how well vibrations travel
through the bedrock in area surrounding the earthquake).
The scale used for this map represents different
levels of horizontal ground shaking that have a one-in-ten
chance of being exceeded in a 50 year period (shaking
is expressed as a percentage of acceleration due to
gravity). High values of probable ground motion (shown
in red) correspond to areas with highest hazard. Low
values (shown in white) correspond to areas of lowest
hazard. The areas shown in white are not free from
earthquakes - instead strong earthquakes that cause
signficant ground motion are very rare events in those
areas.
The map was produced by the United States Geological
Survey. Insurance companies use these maps to set
insurance rates, building designers use the maps to
determine where buildings need an extra measure of
reinforcement, the US government uses these maps to
allocate earthquake training and preparedness budgets,
and the Environmental Protection Agency uses these
maps to set standards for constructing critical facilities
such as power plants or waste disposal sites. For
more information visit the USGS
Earthquake Hazards Program website.
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