The San Francisco earthquake, which occurred 100 years ago on April 18, was one of the worst catastrophes in U.S. history. The financial damage, according to the National Geophysical Data Center, was $24 million in direct quake losses and $500 million in fire losses (which would be more than $10 billion today), and insured losses of $235 million at the time (equivalent to $4.9 billion in 2005 dollars).

Earthquakes in the U.S., while most commonly associated with California, have occurred in 39 states over the last 100 years, and have caused damage in all 50 states. According to the Insurance Information Institute, there are about 5,000 earthquakes each year. The potential cost of earthquakes is on the rise due to burgeoning urban development in seismically active areas and weak older buildings that may not have been built or upgraded to current building codes. An earthquake is unique when compared to other disasters like hurricanes because there are no seasons or warnings. They can happen almost anywhere, anytime.

While earthquakes are not covered under standard homeowners' or business insurance policies, coverage is available in the form of an endorsement to a home or business insurance policy, said Jeanne. M. Salvatore, senior vice president of I.I.I. California homeowners can get coverage from the California Earthquake Authority, a privately funded, publicly managed organization. Yet only about 13 percent of homeowners currently buy the coverage, she said.