Crossposted with TheGreenGrok.
In recent years oil and gas production has been on the rise in the United States. So have minor earth shakes. Is there a link?
Just how much has seismicity increased? Here are the numbers of earthquakes of magnitude 3 or greater over the past few decades:
Considered "minor," magnitude 3 quakes are rarely strong enough to do damage but typically large enough to be felt.
Interestingly, over the same period that the number of these types of quakes has been rising, the United States has seen a rather sizable increase in the extraction of oil and gas.
So is oil and gas production causing the uptick in the country's shaking? Could it be that the increase in earthquakes is specifically tied to the growing practice of using hydraulic fracturing (fracking) to release oil and gas from shale and other tight formations? And what about the high-pressure injection of wastewater from the production into geologic formations at a mile or more beneath the Earth's surface?
In a recently released abstract for an upcoming study, government scientists credit the seismicity to oil and gas activities: "While the seismicity rate changes described here are almost certainly manmade, it remains to be determined how they are related to either changes in extraction methodologies or the rate of oil and gas production.
In an article on the Interior Department's website, David J. Hayes, the department's deputy secretary, sounds a different cautionary note, writing:
The good news for now is that there's no evidence that either extraction or disposal activities have given rise to a major earthquake (with a magnitude of seven or above).4 Nevertheless, I wouldn't be surprised if there are folks in America's heartland who are wondering if the oil and gas companies are doing things right. Sleep tight.
"Is the Recent Increase in Felt Earthquakes in the Central U.S. Natural or Manmade?" - Interior Department article
1 Midcontinent is defined here as 85 degrees to 108 degrees West, 25 degrees to 50 degrees North, or the area roughly bracketed from Ohio to Colorado and North Dakota to Texas.
2 The magnitude of an earthquake is a measure of its size based on the amplitude of the seismic wave it generates. Because the value is logarithmic, small differences in magnitude numbers are a lot bigger than they might look: "each whole number increase in magnitude represents a tenfold increase in measured amplitude." Earthquakes measuring 8 or above are considered "great" quakes; major quakes are in the 7 to 7.9 range; 6 to 6.9 quakes are considered "strong." (More here.)
3 The numbers here are an annual average.
4 One of the largest quakes to hit the U.S. midcontinent -- with a magnitude of 5.6 -- was excluded from the study. The USGS has indicated that it was natural, but it appears to still be under investigation.
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