When companies drill for oil and natural gas, they'll often pump millions of gallons of water into the earth to extract those resources.
But disposing of all this water isn't without consequence: Injecting it deep underground can trigger earthquakes.
And now, for the first time ever, researchers are accounting for such human-induced earthquakes in maps that predict temblor risk areas across the US.
A typical fracking well in the Marcellus Shale of Pennsylvania uses 4.5 million gallons of water, according to the US Geological Survey.
More companies are trying to reuse what they pump, but most of the excess gets pumped down into a different well, called an injection well, under high pressure. This forces the water deeper than sources of drinking water, sometimes miles below the surface.
However, injection wells force much more water into the ground than fracking itself and can put pressure on faults hidden deep in the earth.
A boom in fracking has increased injection well activity over the last several years, and as a result scientists aredetecting more and more human-caused quakes.
A new report from a team of USGS scientists, published March 28, takes human activity into account and estimates how likely it is that areas of the US will experience an earthquake in 2016.
About 7 million people live near an area where these human-induced earthquakes could occur this year, the researchers report. Arkansas, Colorado, Kansas, New Mexico, Oklahoma, and Texas are at the highest risk for these kinds of quakes.
The map below shows the likelihood of quakes this year, with the highest chance of predicted damage highlighted in red. You can see how Oklahoma is becoming as likely as California to experience damaging earthquakes::
Out west, the chance of damage doesn't change much when you consider the risk posed by human activity.
The central US was a different story. When the team incorporated human-induced quakes into models for that region, where natural earthquakes are infrequent — but injection wells are common — the risk of damage in some areas increased more than three-fold, according to the report.
Below is another map from the report. In the central US, you can clearly see the connection between injection wells and earthquakes. The number of wells that have been associated with earthquakes (shown in blue) is especially high in Oklahoma:
The largest human-induced earthquake in the US so far was a magnitude 5.6, which occurred in central Oklahoma in 2011. A study linked that quake to nearby wastewater injection wells.
Mark Petersen, chief of the USGS' National Seismic Hazard Mapping Project and lead author of the report, said during a press conference that he hopes people can use their maps to update building codes and better prepare for earthquakes — particularly ones that humans are now causing.
"We do want to help people understand how much concern they should have with these earthquakes," he said, "and what they should be concerned about."
http://www.techinsider.io/map-human-induced-earthquakes-usgs-2016-3
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