(Carolyn Kaster/AP)

At 6:47 a.m. on Saturday, thousands of birds took flight across the state of Oklahoma. Weather radars lit up with blue and green, signifying that a large number of birds suddenly became airborne at nearly the same time. Then at 7:02 a.m., a 5.6-magnitude earthquake struck the state, originating in Pawnee County.

The culprit was hydraulic-fracking, specifically the deep well injection of fracking wastewater. But what makes this story so interesting is how much warning time the avian residents had before their human counterparts. The vibrations — or pre-vibrations? — prompted the birds to take flight 15 minutes before seismometers detected the earthquake.

Radar catches birds taking off during earthquake Saturday

It’s interesting but not surprising. Animals can feel earthquakes and tsunamis seconds before they hit. The National Zoo reported animals panicking moments before the earthquake that struck D.C. in 2011.

The animal-kingdom panic before the D.C. earthquake makes complete sense. There are two types of waves that roll through the ground during an earthquake, and the first type is undetectable by humans.

“Very few humans notice the smaller P wave that travels the fastest from the earthquake source and arrives before the larger S wave,” says the United States Geological Survey (USGS). “But many animals with more keen senses are able to feel the P wave seconds before the S wave arrives.”

“As for sensing an impending earthquake days or weeks before it occurs, that’s a different story,” the USGS adds.

So far, researchers haven’t figured out why animals may be able to sense earthquakes minutes, hours and even weeks in advance. But one hypothesis suggests that there’s another type of wave or indicator — like the P-wave — that humans cannot detect but animals can. (After-publish edit: And they might not be able to sense them that far in advance at all — we don’t know for sure!)

This question is not just interesting from a zoological standpoint: It could mean there’s something happening minutes, hours or even weeks in advance that humans could use as a warning of an impending earthquake.

The governor declared a State of Emergency in Pawnee County, the epicenter of the quake, and the Oklahoma Corporation Commission ordered the shutdown of 37 wells in the vicinity. No major damage or serious injuries were reported.

The number of earthquakes in regions where fracking is occurring has been increasing at an alarming rate. For years, there had been uncertainty as to their origins, but recent research by the USGS concludes that fracking does cause earthquakes. Both the process of breaking up or “fracking” of the rock to extract oil and gas and the injection of wastewater deep below drinking water aquifers are cited.

Fracking has redrawn the earthquake hazard map of the United States and has put many more people at risk. Earlier this year, a study showed that around 7 million people now live and work in areas that are at risk for shaking due to human-induced earthquakes. “The chance of damage from all types of earthquakes is similar to that of natural earthquakes in high-hazard areas of California,” USGS wrote.

One goal of the report was to help assist threatened communities prepare for the heightened risk of earthquakes caused by fracking. Government officials and emergency managers will be more informed, and engineers can use the information to evaluate the safety of buildings, bridges, roads and other infrastructure.