Risk of earthquake increased for one-third of US

Published on NewsOK Modified: July 18, 2014 at 4:36 am •  Published: July 17, 2014
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WASHINGTON (AP) — A new federal earthquake map dials up the shaking hazard just a bit for about one-third of the United States and lowers it for one-tenth.

The U.S. Geological Survey on Thursday updated its national seismic hazard maps for the first time since 2008, taking into account research from the devastating 2011 earthquake and tsunami off the Japanese coast and the surprise 2011 Virginia temblor.

The maps are used for building codes and insurance purposes and they calculate just how much shaking an area probably will have in the biggest quake likely over a building's lifetime.

The highest risk places have a 2 percent chance of experiencing "very intense shaking" over a 50-year lifespan, USGS project chief Mark Petersen said. Those with lower hazard ratings would experience less intense swaying measured in gravitational force.

"These maps are refining our views of what the actual shaking is," Petersen said. "Almost any place in the United States can have an earthquake."

Parts of 16 states have the highest risk for earthquakes: Alaska, Hawaii, California, Oregon, Washington, Nevada, Utah, Idaho, Montana, Wyoming, Missouri, Arkansas, Tennessee, Illinois, Kentucky and South Carolina. With the update, new high-risk areas were added to some of those states.

Also, Colorado and Oklahoma saw increased risk in some parts and moved up to the second of the seven hazard classifications, he said.

There are major faults and quake hazards along the entire west coast, with an increased concern in the Cascadia region around Oregon. Southern Alaska, the big island of Hawaii, the Missouri-Tennessee-Arkansas-Illinois New Madrid fault area and Charleston round out the biggest hazard areas.

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