As Mark Petersen, chief of the USGS National Seismic Hazard Mapping Project, explains, "In the past five years, the USGS has documented high shaking and damage in areas of these six states, mostly from induced earthquakes."
According to the USGS report, the major cause of earthquakes in these areas is hydraulic fracturing, or fracking, the method of cracking rock formations to extract oil and natural gas by using a highly-toxic mixture of chemicals and water applied under extremely high pressure. The fracking process includes the necessary disposal of wastewater, which is currently pumped deep below ground.
This unnatural injection of massive amounts of highly-poisonous fluids alters pressures inside the lithosphere causing below-ground movements that also shake the surface.
The USGS said the states at highest risk of petroleum-extraction induced seismic activity are Oklahoma, Kansas, Texas, Colorado, New Mexico and Arkansas. Oklahoma and Texas are the states with the highest population levels exposed to human-triggered earthquakes.
The fracking method remains highly controversial. Said to make the United States free of relying on foreign governments for oil imports, it simultaneously pollutes ground, surface water and the air, and now, according to the USGS study, increases the likelihood of dangerous seismic activity as well.