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Hungry for more stories on science, culture and technology?Check out Brain Food: Insights and Discoveries from Northern Arizona. From ground breaking scientific research to global music projects, Brain Food profiles some of the unique projects happening in the region and the interesting people behind them. While there are no new episodes of Brain Food, we will continue to maintain the archive here.

Brain Food: Did The Earth Just Move?

Arizona Earthquake Information Center

This region is not a place known for powerful earthquakes, but over the last year or so, there have been some memorable ones: the kind that wake you from a sound sleep and set your heart racing. Are they leading up to something bigger? Geologist Paul Umhoefer doesn't think so.

"We have some of the least potential to have large earthquakes in Arizona out of all the western states," Umhoefer says. "However, there is a whole series of faults. There are a system of faults from southwest of Flagstaff, through Flagstaff, up toward the Grand Canyon that we know can produce earthquakes."

Umhoefer teaches geology and plate tectonics at Northern Arizona University. He says underground movement is so slow here - just 1 to 2 millimeters annually - that most quakes and tremors are undetectable to humans. By comparison, California's San Andreas Fault shifts about 2 inches per year, producing around 1,000 quakes a month.

"Using GPS and other instruments," Umhoefer says, "we can barely measure any motion of the earth's crust in Arizona east of Lake Mead and the edge of the Colorado Plateau. The mystery is why are all these faults active in the Flagstaff to central Grand Canyon region?"

Umhoefer speculates it could be the effects of a slowly stretching Colorado Plateau or left over tension from the faults that shaped the region millions of years ago. And while there are dozens of quakes and tremors each year in northern Arizona, he doesn't anticipate too many will be strong enough to knock the books off our shelves in the middle of the night.