Why is Oklahoma having earthquakes? Does the state have a major fault line?
Residents around Oklahoma City were rocked by a series of earthquakes late Friday into Saturday with the strongest reaching a M4.4. What’s the cause?
Residents of the Oklahoma City metro area experienced a series of earthquakes late Friday and into Saturday morning. The strongest was a magnitude 4.4 according to the US Geological Survey.
This latest “strong shaking” comes after a rash of tremors in recent weeks. “There has been activity along this fault in the last month starting on December 29, with 5 events between M1.0-1.6 between December 29 and January 6,” the Oklahoma Geological Survey said in a statement on Saturday morning.
“The seismicity from the last decade indicates there were 3 M4.0 or greater events in 2015 and 2017, corresponding to a time period when wastewater disposal volumes were higher,” the agency added warning that “the seismic hazard remains high in the area.”
It is advising citizens to “secure valuables that might shake during possible strong aftershocks and practice Drop, Cover, and Hold On in the event of damaging events.”
Why is Oklahoma having earthquakes?
The US Geological Survey says that Oklahoma experienced a surge in seismicity starting in 2009. The rate of magnitude 3 and larger earthquakes from 2014 through 2017 even exceeded that of California. The surge was not a result of hydraulic fracking, which did cause some, the largest of which registered magnitude 3.6 in 2019.
Instead the majority of the increased seismicity was induced by oil and gas related process, specifically the industrial practice known as “wastewater disposal.” This is where “fluid waste from oil and gas production is injected deep underground far below ground water or drinking water aquifers.” Of the waste water that has been injected in the ground in Oklahoma, over 90 percent was a byproduct of oil extraction process and not waste frack fluid according to the US Geological Survey.
The Oklahoma Corporation Commission said on Saturday morning that its Induced Seismicity Department is researching the quakes. “The quakes that occurred years ago (2014-2017) in the area were linked to oil and gas wastewater disposal wells that used the deep Arbuckle formation. They were shut down by the OCC years ago. Hydraulic fracturing has been linked to quakes in other areas, but there are no such activities in the Arcadia area,” the agency said.
Does Oklahoma have a major fault line?
Oklahoma has a series of fault lines that run through the state which have been mapped out by the US Geological Survey. The two which are most likely to affect the state are the Madrid Fault and the Meers Fault. The former is centered around the Boot heel region of Missouri and the latter is located near Lawton in southwestern Oklahoma.
While damage from an earthquake can start at magnitude 4, the US Geological Survey says that magnitude 4.9 may be felt by many typically only cause disturbances. Above that level, generally cause damage. The largest earthquake recorded in Oklahoma was magnitude 5.8 near Pawnee in September 2016.