An earthquake zone covering part of southern Illinois has been surprisingly still lately, according to new research published in Science magazine.

The New Madrid fault has rocked the Midwest every 500 years or so … the last major quake was in the 1800s. But Northwestern University seismologist Seth Stein says, that may be it for a while … like tens of thousands of years.

STEIN: People say it’s not if, but when a giant earthquake’s gonna happen again. Actually, there’s no science reason to believe that.

Stein says G-P-S readings show the ground near the fault has been essentially motionless for almost 2 decades. That’s not what he’d have expected if the fault were storing up energy for another big quake. The findings suggest that continental faults like the New Madrid play by very different rules from faults on the coasts.