WASHINGTON >> The federal government has increased its estimate of the threat to Hawaii from earthquakes in an updated seismic hazard map.
Hawaii is among of 16 states that have the highest risk for earthquakes. The other states are Alaska, 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.
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.
The U.S. Geological Survey said the national seismic hazard maps had not been updated since 2008. The new maps take 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.”
Much of the country west of the Rockies, along with parts of Oklahoma and Tennessee and sections of central Arkansas, northern Alabama, Georgia, South Carolina, Indiana, Illinois, Ohio, Michigan, Virginia, New York and New England saw an increase in shaking hazards for small buildings like houses.
At the same time much of North Carolina, the northern tip of South Carolina, patches of Texas, New Mexico, Oregon, Utah, Nebraska, Arkansas, Kentucky, Tennessee, Ohio, Pennsylvania and New York saw hazard levels lower slightly. And using a different type risk analysis for tall buildings the shaking hazard in New York City dropped ever so slightly, Petersen said.
Petersen said the maps sidestep the issue of earthquakes created by injections of wastewater from oil and gas drilling in Oklahoma and other states, saying those extra quakes weren’t included in the analysis. So far this year, nearly 250 small to medium quakes have hit Oklahoma.
Much of the research and cataloging was done by the nuclear industry in response to the quake and tsunami that crippled Japan’s Fukushima reactor. And researchers at the University of California, Berkeley came up with a better model to simulate shaking, Petersen said.
“I see it as a big improvement,” said Cornell University seismologist Rowena Lohman. “They brought in more information.”
USGS map: http://pubs.usgs.gov/of/2014/1091/