Half of U.S. homes at risk from natural disasters

More than half of all U.S. homes are located in areas prone to tornadoes, earthquakes or hurricanes.

About 71 million housing units, or 55 percent of the nation's total, fall into the high risk category, with 10.6 million of these, or 8 percent of the total, classified as very high risk, according to a report from RealtyTrac.

The report is based on historical and predictive data from the U.S. Geological Survey and the National Oceanic and Atmospheric Administration regarding the likelihood of a given county being hit by a 5.0 magnitude or greater earthquake over the next 50 years or highly destructive hurricanes and tornadoes. (See here for an interactive county-by-county map that assesses housing risks around the U.S.)

"It's fairly obvious from looking at the map that these high-risk areas tend to be places where a lot of people want to live, like along the coast," said Daren Blomquist, vice president at RealtyTrac, which provides real estate data. "While we're not expecting this to cause a mass exodus from those areas, at least when home buyers are looking at a house they should take it into consideration along with the other factors that can affect home value."

Higher-risk areas around the country -- such as San Diego and Riverside counties in Southern California, Manhattan and Brooklyn in New York, and the Boston metro area -- generally have higher home prices than lower risk regions. Median home prices in the eight counties adjudged as being at low risk for natural disasters averaged $161,000 in April, while prices in the 12 high-risk counties averaged $377,483, according to RealtyTrac.

The highest-risk parts of the country are mostly in "tornado alley" in northern Texas, Oklahoma, Kansas and Nebraska. Other states prone to tornado activity include Alabama, Arkansas, Georgia, Indiana, Mississippi, North Carolina, Ohio and South Carolina.

Some 51 counties in the U.S. with a population of 100,000 or more are classified by RealtyTrac as being at "very high risk" of twisters. The median home price in these areas as of April averaged $120,972, 30 percent below the national median home price of $172,000.

For its analysis, RealtyTrac assigned each county a score of 15 to 75 based on its score in each of three equally weighted risk categories: earthquakes, hurricanes and tornadoes. Owing to the nature of natural disasters, the risk scores are based on very broad measures. For example, the earthquake score is based on a model used by the Geological Survey that calculates the probability of a 5.0 magnitude earthquake occurring within 30 miles of that county over the next 50 years.

In other word, even if you're living in Lee, Alabama, one of the counties in the highest-risk category, you might never see a tornado.

Blomquist said RealtyTrac is also gathering information about the risks posed by wild fires and flooding and hopes to include that in future versions of the report.

"We hope homeowners will apply this information by taking steps to protect, to the extent that they can, what is usually their biggest asset -- their house -- from potential damage, or even destruction in the worst-case scenarios, from these natural disasters," he said. "No. 1 is making sure it's insured properly, particularly if you're in a high-risk area. No. 2 is making improvements, to the extent that you can and is financially reasonable, to have that property in a condition that it can withstand that natural disaster."