Oklahoma Seismologist: Saturday's Earthquakes Are Naturally Caused

Alex Cameron, News 9

OKLAHOMA CITY -- Not only was Saturday night's earthquake historically strong, it comes during a period of historic seismic frequency -- hundreds of earthquakes a year, when we used to get just one or two.

11/5/2011 Related Story: More Aftershocks Sunday, After Oklahoma's Largest Earthquake Saturday

11/5/2011 Related Story: 4.7 Magnitude Earthquake, Aftershocks Rumble Through Oklahoma

The question our Oklahoma Impact Team has been looking into--what's causing it all?

There's been a lot of speculations in the earthquakes we've been experiencing in central Oklahoma for the last two years.

The so-called Jones earthquakes are being caused by fracking or other related oil and gas well activity. There are known cases in the U.S. of high pressure injection, or disposal, wells causing small earthquakes.

Researchers from the Oklahoma Geological Survey haven't completely ruled that out with the Jones quakes, but said the evidence suggests they are naturally occurring.

In the case of this weekend's quake, they're even more convinced it was naturally caused, because it was so much larger, and it occurred right on a known fault.

"So it's very different from the Jones earthquakes where we don't have a clear fault that the earthquakes are occurring on," said Austin Holland, research seismologist at the Oklahoma Geological Survey.

Holland said fortunately, they put several measuring instruments out in the epicentral area Saturday afternoon, in response to Saturday morning's smaller quake, giving them detailed data on Saturday night's big one.

"It's a complex fault, so we can learn a lot about the fault system itself," Holland said.

And hopefully, he said, get a better idea whether it could produce an earthquake that's even stronger.

Experts said the two earthquakes yesterday were definitely related since they occurred on the same fault and in almost the exact same spot.

Don't be surprised if you experience some aftershocks. Experts said they can occur days, weeks or even months after the initial quake.