Despite concerns, new study shows no shift in Midwest faults

The earth under the New Madrid Seismic Zone either isn’t shifting or is barely shifting at all, say three independent university analyses of a global positioning system stations stuck in the ground and monitored for a decade. The St. Louis Post-Dispatch’s recent story said the cataclysmic shifts of past earthquakes remain unexplained, the mechanism for future earthquakes still a mystery.
The results contradict a study by the University of Memphis. The university study made headlines in June when it said that two GPS stations on opposite sides of the Reelfoot fault had moved closer to each other at a rate that rivaled faults in California. The compression could coil up the faults for future earthquakes.

Eric Calais of Purdue University, said that the University of Memphis results had to be a statistical anomaly, probably an instrumental error, and, regardless, not anywhere close to the motions of the San Andreas fault.

University of Memphis author Michael Ellis, said his group was only trying to show that the motions are consistent with the level of seismic hazard that geologists have already established for New Madrid.

Ellis’ paper was the first to suggest that the plate is stretching and straining near New Madrid, Mo. All four groups agree that the tiny motions they’re arguing about, as much as an eighth of an inch per year, would need to be almost twice as big to build up the strain needed to unleash the huge magnitude 7 or 8 earthquakes that occurred in 1811 on the New Madrid Fault and at regular 500-year intervals for the past few thousand years.

Purdue’s Calais questioned the findings suggesting that either the past earthquakes weren’t as big as geologists thought, the earthquake process has stopped, or it’s in a quiet period that could suddenly start up again.

Officials are trying to decide how important the earthquake hazard is in light of conflicting studies. Fewer than 41 percent of Missourians have earthquake insurance according to Missouri Gov. Matt Blunt.

In Missouri, the percentage of homeowners with earthquake insurance varies wildly, and is not necessarily connected to how close the homeowner is to New Madrid.