The state was hit by an earthquake measuring 4.5 in magnitude a little after 1 a.m. CDT, causing no apparent damage or injury. The quake, according to the U.S. Geological Survey, was located eight miles Northwest of Ottawa, Ill., and 71 miles west-southwest of Chicago.

Don Griffin, vice president of Commercial Lines for the Property Casualty Insurers Association of America based in Des Plaines, Ill., said insurers always place moratoriums on writing new business after a catastrophic event.

The Illinois earthquake, while not a catastrophe, would probably see a moratorium. Insurers, he explained, do not want to place insurance on property where aftershocks could still cause damage. They also want time between the last tremor and the binding of a new policy to be comfortable that any damage reported was not from an old event.

Only a few states have regulations covering the moratoriums, but where there are none, companies must file their moratorium rules with regulators, he added.

"The actuarial odds of it happening here [in Illinois] are within reason, and carriers feel they can go ahead and insure the risk, unlike other areas [such as California] where its more probable and they worry about it more," said Chuck Schramm, a producer with the insurance firm Lamb Little & Co. Ltd., in Rolling Meadows, Ill., and a teacher of insurance education courses in the state. "But if you think about the hedge [carriers] have with the deductible, it's not a bad bet for them to take."

The deductible is based on the value of the property and can usually run in increments of two, five or 10 percent. The insurance coverage typically does not cover homes with masonry veneer covering more than 10 percent of the house. However, he said, it can be purchased as an add-on to coverage.

On the commercial side, structures of more than four stories have to wait one week for the coverage to take effect and are subject to the same deductible coverage based on property value, he noted. The policy is written as a separate cause of loss, unlike homeowners insurance where it is an endorsement.

According to the USGS's Web site, Illinois has seen a number of earthquakes over the centuries, primarily in the area of the New Madrid fault. The most famous earthquake to hit the Midwest was in the early 19th century. The event was so severe that seismic activity caused the Mississippi River to appear to flow backwards for a number of days.

The New Madrid fault line begins in Cairo, Ill., and runs south through the state for 120 miles into Arkansas, and parts of Kentucky and Tennessee. Monday's earthquake hit further north, which is rare, and was felt into neighboring Wisconsin.

Dennis Garrett, executive vice president for the Professional Independent Insurance Agents of Illinois, said that earthquake insurance is something that is on the minds of many homeowners because of the New Madrid fault.

Mr. Garrett said earthquake insurance is available to homeowners but only as an endorsement on the policy. Some companies refuse to write it, especially where the homes are located in the south of the state in the vicinity of the fault. The alternative is through excess and surplus lines, which he noted can prove to be very expensive.

Mr. Schramm, said that when there is an event, whether it is an actual earthquake or just a prediction of one, "all the insurance companies get cold feet and they want to wait" before they resume writing new business.

Within six months to a year companies ease up on their restrictions, "and become pretty open," to writing policies again, he said.

Gary Kearney, assistant vice president for Property Claim Services, a division of Jersey City, N.J.-based Insurance Services Office Inc., said that from all indications there was little damage from the quake, but there remains the threat of something bigger happening at some point, unlike California where the threat appears to be more imminent.

So far this year, despite storm damages in Wisconsin and other Midwest states, losses have been less than last year.

However, some see the potential for catastrophic damage from an earthquake as very real, if not imminent.

"When you think about the historical issue, at some point in time the New Madrid fault will move again with a big quake, that is what all the scientists say," observed Mr. Schramm. "It is going to be horrendous event. It's not a question of if, but when."