As for the likelihood of such an event occurring, RMS says, “Numerous scientific issues have been raised regarding the level and uncertainty of seismic hazard in the New Madrid Seismic Zone and the surrounding region of the Central United States.” But there is broad agreement regarding evidence of repeated large earthquakes there in the last several thousand years, RMS says.

“Moreover,” the report continues, “ongoing seismicity rates suggest a 28 to 46 percent likelihood of a magnitude 6.0 or greater earthquake in the broad region around New Madrid in the next 50 years.”

As part of its analysis, RMS analyzed potential losses from a series of scenarios for both moderate and large earthquakes throughout the New Madrid region, using events generated from the modeler's U.S. Earthquake Model.

The range of insured losses for these scenarios was between $7 billion and $33 billion for a magnitude 6.5 earthquake at 20 different locations throughout the Wabash Valley, to between $123 billion and $306 billion for a magnitude 6.6 earthquake directly beneath St. Louis.

RMS also looked at exposure values for six urban centers in the area: Indianapolis, Ind.; St. Louis; Louisville, Ky.; Nashville, Tenn.; Memphis, Tenn.; and Little Rock, Ark. Combined, these centers have total exposure value of $1.14 billion. The eight-state region making up the area has total exposure value of $8.95 billion.

RMS says 2011 marks the 200th anniversary of the first in a sequence of three magnitude 7.0 or greater earthquakes that occurred over a 54-day span in 1811 and 1812 along the Mississippi River near the town of New Madrid.

The catastrophe modeler says analyses of the area show that the earthquake sequence was not an isolated event, and the New Madrid Seismic Zone is believed to have produced repeated sequences of major earthquakes.