When it comes to earthquakes, Oklahoma is the new California.
The Sooner State may be better known for tornadoes. But since October, Oklahoma has had more quakes than California, knocking the Golden State out of first place in the lower 48 states.
It's not even close, actually. Since Oct. 1, California has had 139 earthquakes of magnitude 3.0 or larger, according to federal data. Oklahoma has had 189.
In 2014, Oklahoma has had twice as many quakes as California, though it's only half the size.
The U.S. Geological Survey and academic researchers have linked much of the increase in Oklahoma to deep injection of waste fluid from oil and gas production in the drilling-heavy state.
State and federal officials issued a rare warning Monday about the increased danger of a major earthquake (EnergyWire, May 6). The statement from the USGS and the Oklahoma Geological Survey said the rate of earthquakes in Oklahoma has soared by 50 percent since October. The agencies warned that the risk of a damaging magnitude-5.5 or larger quake has gone up "significantly."
The statement also noted that deep injection of wastewater from oil and gas production is a "likely contributing factor."
The high-volume hydraulic fracturing that is driving the resurgence in domestic oil and gas production has caused a surge in the amount of toxic drilling wastewater that companies usually dispose of in deep wells.
A study released last week at the Seismological Society of America's annual meeting pointed the blame for many of the quakes around Oklahoma City at four specific disposal wells (EnergyWire, May 2). The owner of the wells doesn't use high-volume hydraulic fracturing but instead specializes in "dewatering" formations to get oil. That also creates large amounts of wastewater.
The study by Cornell University geophysicist Katie Keranen linked the wells to the Jones swarm, named after a northeastern suburb bordering Oklahoma City. Hundreds of small quakes have been recorded in the area since 2009.
There's also been a lot of shaking to the northwest of Oklahoma City, between Enid and the Kansas border. That's where drilling companies are using high-volume fracturing to tap the Mississippi Lime Play for oil. Southern Kansas has been experiencing earthquakes as well.
The state's biggest earthquake, a magnitude-5.7 rupture in 2011, was centered east of Oklahoma City near Prague. It injured two people and damaged more than 200 homes and businesses. The USGS released research earlier this year indicating it was likely the largest earthquake ever linked to underground injection (EnergyWire, March 7).
This year, Oklahoma has had 147 earthquakes magnitude 3.0 and larger, according to data retrieved from the USGS database and analyzed by EnergyWire. California has had 70.
Compare that with the period between 1978 and 2008, when the rate in Oklahoma was two such quakes a year.
EnergyWire's review of earthquake data looked at onshore earthquakes of magnitude 3.0 or greater because that is the strength at which most earthquakes in the United States can be felt and reliably recorded. There are more seismic monitors on the East and West coasts, so many smaller earthquakes are recorded in those areas.
Seismologists have also linked earthquakes in Arkansas, Colorado, Ohio and Texas to injection of wastewater from oil and gas production. Man-made earthquakes can be more damaging at the same magnitude, researchers noted in a recent study, because they occur closer to the surface.
The issue has grown worrisome enough to state oil and gas regulators that agencies from 10 states have expressed an interest in participating in a work group on the topic being assembled by the Interstate Oil and Gas Compact Commission and the Ground Water Protection Council (EnergyWire, April 30).
Oklahoma has long been known to have more earthquakes than some other inland states. But the state and federal seismologists said Monday that the sudden spike in the earthquake rate cannot be explained by natural fluctuations.
Oklahoma and California are both far behind Alaska, which had a little more than 1,000 such earthquakes last year.
But Californians take their earthquakes seriously. And some might not like being upstaged by a state in the middle of the country. That could be particularly true, one Californian said, in Parkfield, where signs proclaim it's the "Earthquake Capital of the World."
"They might have to change the signs in Parkfield," joked Don Drysdale of the California Department of Conservation. "They'd probably be pretty upset to lose the title."
Click here to see a map of Oklahoma seismicity and here to watch animation of Oklahoma seismicity.