Federal and state seismologists on Monday warned that the risk of a damaging quake occurring in central and north-central Oklahoma had increased dramatically.
The state’s earthquake rate has increased 50 percent since October 2013, according to the joint warning by the U.S. Geological Survey and Oklahoma Geological Survey. A likely contributing factor is waste fluid from disposal wells used by the oil and gas industry, a link federal and university seismologists have made in several peer-reviewed studies.
Bill Leith, USGS Senior Science Advisor for Earthquakes and Geologic Hazards says the warning is not a forecast.
“Because earthquake sequences are statistically abnormal behavior, when you get a large increase in the number of small earthquakes, the potential for a larger earthquake also goes up,” Leith tells StateImpact.
The warning is rare for Oklahoma; most of the federal agency’s warnings are for California, Leith says. The risk posed by earthquakes in Oklahoma is magnified by how most of its homes and buildings are built, Leith says.
“Oklahoma has a lot of construction which is not build to withstand strong earthquake shaking,” he says. “We saw damage in that type of construction in the November 2011 Prague earthquakes.”
That quake, a 5.6-magnitude temblor that injured two people and damaged more than a dozen homes, was Oklahoma’s largest ever recorded. Several published studies — the most recent in March 2014 — have linked that earthquake sequence with nearby oil and gas disposal well, which are used to store waste fluid from hydraulic fracturing, or “fracking,” and other types of drilling.
Oklahoma has been experiencing an earthquake “swarm” for several years. In October 2013, the USGS said the state’s “hazard” had increased due to more frequent shaking.