The earth is shaking in Oklahoma. But why?

The Meers fault in Southwestern Oklahoma.

There were 179 earthquakes in Oklahoma in just the last 7 days. Which is crazy. What's more the frequency of earthquakes in the state has dramatically increased since 2004. What was once a freak occurrence has become so common that I'm now more accustomed to hearing about earthquakes from family in Oklahoma than from friends in California. So what gives?

Earthquakes happen all the time in places where you don't expect earthquakes to happen. If you read an interview I did in 2010, you'll learn that Oklahoma does have plenty of faults and the state has been recording earthquakes since anybody started keeping records. The ground shaking at all: That's completely normal. This sharp increase in frequency and size of quakes, though, is weird. Last October, the Oklahoma Geological Survey released the results of a study that suggested these changes in how Oklahoma experiences earthquakes are different from what you'd expect as a part of natural variation.

In other words: These earthquakes could be triggered by human activity. If that's what's happening, then the likely culprit is the disposal of wastewater from fracking operations. A National Academy of Sciences report, published in 2013, determined that the liquid can lubricate existing faults and/or change the pressure around those fault lines in such a way that it causes them to move. There aren't many earthquakes that have been clearly and cleanly attributed to this effect, but given how difficult it can be to disentangle natural processes from the effects of man-made triggers that induce natural processes, that fact doesn't really mean that the injection of wastewater has only contributed to a small number of quakes. But it's also true that we don't have the evidence to say, "Wastewater disposal is causing all these quakes."

Meanwhile, oil and gas-producing states are mostly ignoring the oversight recommendations made by the NAS report. Although, on Monday, the governor of Kansas appointed a committee to study whether some of the quakes that have happened along the Kansas/Oklahoma border can be linked to wastewater disposal.

So what now? Until any kind of regulatory action gets taken, it's basically just fallen to Oklahomans to get used to the ground shaking. Earlier this week, the Red Cross launched an Oklahoma-centric earthquake app that not only educates people on how to respond to a quake, but also helps them track activity near friends and family and make quick contact in case of an emergency.