Man-Made Quakes Set Stage for Larger Earthquake in OklahomaApr 1, 2016
Parts of Oklahoma and Kansas are just as likely to experience a large, destructive earthquake as the highest-risk areas in California, a United States Geological Survey suggests. The New York Times reports that the agency has released a map of earthquake risks that considers human-made quakes for the first time. "By including human-induced events, our assessment of earthquake hazards has significantly increased in parts of the U.S.," said Mark Petersen, chief of the USGS Natural Seismic Hazard Mapping Project. The map suggests that the increasing number of small human-induced quakes may lead to a large destructive one in the future. According to the USGS, the greatest risk is in a rural area along with Oklahoma-Kansas border.
Drilling activity results in earthquakes because the large amounts of toxic wastewater are injected deep underground. These wastewater injection wells increase the pressure on faults, and lead to tremors.
The number of quakes has increased with drilling activity. According to NYT, Oklahoma experienced some of its largest quakes in state history this year, with magnitudes of 4.7, 4.8 and 5.1. The Oklahoma Corporation Commission placed significant restrictions on underground wastewater disposal in February and March. Since then, the number of quakes seems to have slowed; there were 160 quakes with a magnitude 3 or above this year.
The state experienced 907 quakes at magnitude 3 and above, the level at which quakes can be felt, last year. To put this into context, Oklahoma used to have less than 2 such earthquakes each year. Kansas has also seen a substantial rise. There were 54 earthquakes in the state last year at magnitude 3 or above; previously, it experienced even fewer quakes than Oklahoma.