Scientists, regulators and technical experts from the energy industry met in Oklahoma to discuss how earthquakes triggered by oil and gas operations should be accounted for on national seismic hazard maps, which are used by the construction and insurance industries and pubic safety planners.
The three-day workshop started Nov. 17 and was co-hosted by the Oklahoma Geological Survey and the U.S. Geological Survey.
Currently, the National Seismic Hazard Maps don’t include “non-tectonic” earthquakes, like those that could be triggered by disposal wells or hydraulic fracturing. Through the workshop, federal seismologists solicited input on how manmade quakes should be accounted for on national hazard models.
Earthquake activity is surging in Oklahoma. More than 450 magnitude-3.0 or greater earthquakes have shaken the state in 2014, four times as many as last year and a new state record.
Peer-reviewed papers in scientific journals have concluded many of Oklahoma’s earthquakes are likely linked to a type of well the energy industry pumps full of waste fluid from oil and gas drilling. There’s still disagreement about the scope and scale of the connection, but most earthquake researchers agree that disposal wells are a contributing factor in at least some of the earthquakes.
The USGS updates its National Seismic Hazard Maps every six years to include the latest information on earthquake activity, faults and earth measurements. The maps and hazard models have wide government and commercial applications and influence local emergency response, insurance rates and building codes.
“Part of the reason we make these is really for the engineering community,” says Justin Rubinstein, a USGS geophysicist stationed in Menlo Park, Calif., who’s studying induced earthquakes. “It’s for designing buildings.”
For engineers and those interested in the risk earthquakes pose to the public and buildings, “it doesn’t matter how big an earthquake is, it all is dependent on the shaking from that earthquake.”
“If you have a magnitude-9.0 that’s 200 kilometers deep, that doesn’t matter nearly as much as a magnitude-6.0 that’s right underneath you,” Rubinstein says.
Earthquake magnitudes are a piece of the puzzle, but the type of earthquake and where it occurs, geologically and geographically, greatly effect the amount of ground shaking a quake generates. Shaking from earthquakes that strike in the western United States, for example, often dissipate more quickly than quakes that strike in Oklahoma and states throughout the central part of the country, Rubinstein says.
Tuesday’s workshop session included presentations from many scientists at the forefront of induced earthquake research, including Bill Ellsworth and Art McGarr with the USGS and Mark Zoback from Stanford University, as well as panel discussions that included state seismologists and oil and gas regulators from Arkansas, Colorado and Kansas — all states that have recorded quakes suspected of being linked to oil and gas activity.
In the past, manmade earthquakes were excluded from the national maps and models because scientists didn’t think they posed a significant hazard. Rubinstein says the large earthquake uptick in Oklahoma and other states — which has included temblors that have damaged buildings and caused injuries — creates an urgent need to assess hazard posed by induced earthquakes.
“With the big increase in the earthquake rate and the occurrence of some damaging induced earthquakes, we realized that we can no longer neglect these earthquakes,” he says.
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