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A timeline map of the massive increase in human-caused earthquakes in Oklahoma

posted by Jason Kottke   Jul 24, 2017

In just the past 10 years, the number of earthquakes in the central US (and particularly Oklahoma) has risen dramatically. In the 7-year period ending in 2016, there were more than three times the number of magnitude 3.0+ earthquakes than in the previous 36 years. Above is a video timeline of Oklahoma earthquakes from 2004-2016. At around the midpoint of the video, you’ll probably say, “wow, that’s crazy”. Keep watching.

These earthquakes are induced earthquakes, i.e. they are caused by humans. Fracking can cause induced earthquakes but the primary cause is pumping wastewater back into the ground. From the United States Geological Survey’s page on induced earthquake myths & misconceptions (a summarized version of this paper):

Wastewater disposal wells typically operate for longer durations and inject much more fluid than hydraulic fracturing, making them more likely to induce earthquakes. Enhanced oil recovery injects fluid into rock layers where oil and gas have already been extracted, while wastewater injection often occurs in never-before-touched rocks. Therefore, wastewater injection can raise pressure levels more than enhanced oil recovery, and thus increases the likelihood of induced earthquakes.

Of course, this wastewater is a byproduct of any oil & gas production, including fracking. But specifically in Oklahoma’s case, the induced earthquakes have relatively little to do with fracking:

In contrast, in Oklahoma spent hydraulic fracturing fluid represents 10% or less of the fluids disposed of in salt-water disposal wells in Oklahoma (Murray, 2013). The vast majority of the fluid that is disposed of in disposal wells in Oklahoma is produced water. Produced water is the salty brine from ancient oceans that was entrapped in the rocks when the sediments were deposited. This water is trapped in the same pore space as oil and gas, and as oil and gas is extracted, the produced water is extracted with it. Produced water often must be disposed in injection wells because it is frequently laden with dissolved salts, minerals, and occasionally other materials that make it unsuitable for other uses.