Well, this complicates hazard planning, but overall it may be good news.
"If earthquakes happen on the Reelfoot fault every 500 years, and have been doing so for hundreds of thousands of years, we would expect to see a mountain range there—but we don't," says Gold. Instead, he suggests the modest fault scarp associated with the Reelfoot fault indicate that the earthquakes haven't been sustained over a long period of time.
. . .
"Our results will hopefully encourage the seismic hazard community to consider the possibility that the tempo of faulting may be variable," says Gold. "Sometimes there may be very long intervals between earthquakes and sometimes the earthquakes may be more closely spaced."
The USGS team hopes their new results on New Madrid ruptures can provide insights to those who model risk and seismic hazard in the region. Gold says that refining and updating seismic hazards with more information on how a fault might rupture can help with building codes—designing buildings just right to keep us safe, but not over-designed, which can waste resources.