Oklahoma used to be a seismic afterthought, a place with so few earthquakes that in the 1990s it was one of three locations where the Soviets were allowed to monitor American nuclear testing. Today, however, Oklahoma is one of the most seismic places on the planet. In 2015, the state had 907 earthquakes that were 3-magnitude or greater compared with just one in 2007. Scientists say the growth in seismicity is directly related to the oil and gas industry, specifically the use of disposal wells that reinject back into the earth salty wastewater that comes up naturally during drilling. An estimated 3 billion barrels of water came out of the ground in 2015, and its reinjection has increased pressure on the state's fault lines, triggering hundreds of tremors in western and central Oklahoma. The state, meanwhile, has been slow to respond. Critics say officials are too reliant on the industry to take any meaningful steps that would put real pressure on the industry, especially at a time when the price of oil has fallen by 70% since 2014. Many Oklahomans are ... concerned that a big one will hit a populated area like Oklahoma City. Of equal concern are the long-term consequences of disposing billions of barrels of water back underground. Some seismologists say that even if all disposal activity stopped in the state immediately, there could be earthquakes for decades.