Twenty years on, the Northridge earthquake remains the costliest U.S. earthquake for insurers, causing $15.3 billion in insured damages when it occurred (about $24 billion in 2013 dollars), according to the Insurance Information Institute (I.I.I.).

The 6.7 magnitude quake, which hit Los Angeles on January 17, 1994, also still ranks as the fourth-costliest U.S. disaster, based on insured property losses (in 2013 dollars), topped only by Hurricane Katrina, the attacks on the World Trade Center and Hurricane Andrew.

On the global scale, the Northridge earthquake still ranks as the second costliest earthquake for insurers, after Japan’s earthquake and tsunami of 2011, according to Munich Re.

While there has been no major earthquake on the U.S. mainland since Northridge, I.I.I. president Dr. Robert Hartwig notes that the potential cost of U.S. earthquakes has been growing because of increasing urban development in seismically active areas and the vulnerability of older buildings, which may or may not have been built or upgraded to current building code.

Still many homeowners do not purchase earthquake insurance. A recent poll by the I.I.I. found that only one out of 10 American homeowners (10 percent) have earthquake insurance, compared with 13 percent in 2012.

In western states, 22 percent of homeowners said they have earthquake coverage, down from 27 percent.

Earthquakes are not covered under standard U.S. homeowners or business insurance policies. However, coverage is usually available in the form of an endorsement to a home or business insurance policy.

As Dr. Hartwig reminds us:

While the cost of insurance has increased since Northridge, it’s important that home and business owners in California and other vulnerable areas consider purchasing earthquake coverage, which is the fastest and most efficient path to recovery.”

Check out additional I.I.I. facts and statistics on earthquakes and tsunamis.