Oklahoma is now the most earthquake-prone state in the nation, considerably outdistancing California, according to the USGS. Yesterday morning a 5.6 in magnitude quake hit northcentral Oklahoma, with shaking felt as far away as Arizona and the Midwest. The record-settling quake has been linked to oilfield wastewater disposal, according to state regulators, who ordered a 500-square mile shutdown in disposal activity Saturday, according to the Washington Post.
Not so coincidentally, the discovery that disposal of liquid wastes underground causes seismicity was first discovered fifty years ago due to an earthquake measured at a very similar 5.3 in magnitude. How that happened was part of one of my favorite story leads a couple of years ago, so forgive me for reposting — it’s a really interesting story.
The U.S. Army had a problem, a big problem: 165,000 gallons of some of the deadliest war materials known to man, including napalm, chlorine gas, mustard gas and sarin, a nerve gas developed by the Nazis, tiny doses of which can kill in minutes. After stockpiling these weapons of destruction for decades in its Rocky Mountain Arsenal near Denver, the government decided the time had come to dispose of the hazardous wastes but didn’t know how.
The solution? In l961, authorities drilled a well 12,000 feet deep, far below any aquifer, and over the next five years pumped hundreds of thousands of gallons of toxic wastes into a cavity in the rock miles beneath the surface.
One problem: Not long after the pumping began, Denver and nearby suburbs began to experience swarms of earthquakes. Most of them were quite small, less than 3 in magnitude, but in a region that rarely experiences earthquakes, 1,300 earthquakes in four years raised questions. Then, in August 1967, a significant earthquake — magnitude 5.3 — shook the city of Denver and the nearby suburb of Commerce, with damages that totaled over $1 million.
The Army stopped pumping the toxic wastes into the injection well. Geologists discovered the liquids had been pumped into an existing fault deep in the “basement” rock. The fault had begun to lose strength and slip, even after the pumping stopped
For city officials, this was alarming, but geologists were intrigued to discover it was possible to trigger earthquakes along existing fault lines, and a team of scientists from the U.S. Geological Survey soon launched into an experiment in an oil field with known earthquake faults in Rangely, Colo. The goal? To learn what volume of fluid pressures were required to trigger earthquakes, and to see if seismic activity could be stimulated and then brought to a halt. The experiment worked, on a small scale, and encouraging results were reported in the journal Science in March of 1976.
“We may ultimately be able to control the timing and size of major earthquakes,” the team, led by C.B. Raleigh and J.H. Healy, speculated. They suggested drilling wells along the San Andreas Fault, and injecting water to release seismic pressures with little earthquakes. They hoped in this way to prevent the legendary “Big One,” an earthquake comparable to the massive and ruinous l906 San Francisco earthquake, which has a 3 percent to 30 percent chance of occurring in the next 30 years in California.
“They actually proposed this idea, to drill wells and pump in water and trigger small earthquakes along the San Andreas,” said William Bilodeau, who chairs the geology department at California Lutheran University in Thousand Oaks. “And they got fairly far along in the planning process and then people began to say, ‘Wait a minute — what happens if we set off a really big earthquake? What’s the [legal] liability?’ ”
The rest of the story is about Ventura County in the present day, which (fortunately!) turns out for geological reasons not to be particularly vulnerable to this kind of oilfield waste disposals.
Taylor Swift’s immortal line comes to mind re: Oklahoma —
Hey now we got problems
and I don’t think we can solve them
But Oklahoma, after years of denying any possible connection between oilfield waste disposal and seismicity, this weekend shut down disposal wells in a vast area — 725 square miles, according to the Tulsa World.