WASHINGTON (AP) -- A new study finds that a major trigger of man-made earthquakes rattling Oklahoma is how deep -- not just how much -- fracking wastewater is injected.
Scientists analyzed more than 10,000 wastewater injection wells where 96 billion gallons of fluid -- leftover from hydraulic fracturing -- are pumped yearly.
They say the amount of wastewater injected and the depth are key to understanding the quake outbreak, which includes the magnitude 5.8 Pawnee quake in 2016.
Thea Hincks of the University of Bristol in England says state regulators could cut about in half the number of man-made earthquakes by restricting deep injections in the ground.
The study only applies to Oklahoma earthquakes. Findings appear in Thursday's journal Science.
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