More Counties Added to Oklahoma Earthquake Watch List

Oklahoma officials are expanding the number of counties that are included in earthquake “areas of interest,” and asking nearly 100 companies to prove their oil and gas waste-water disposal wells are not too deep.

The Tulsa World reports that the Oklahoma Corporation Commission announced the requirements at a meeting in Medford. Well operators in listed counties have been directed to reduce disposal volumes if earthquakes continue to occur in those areas.

Letters were sent last week to 92 companies holding permits for waste-water disposal wells directing them to provide evidence that their wells are not at a depth most likely to trigger earthquakes.

Medford has experienced a number of recent earthquakes that scientific studies have linked to oil and gas disposal wells.

According to Austin Holland, chief seismologist with the Oklahoma Geological Survey, the number of earthquakes that the state has experienced is unusual and “is very unlikely to be naturally occurring.”

The commission said that the counties that experience “seismic swarms,” or multiple earthquakes occurring close together, will now be included in its system of regulating waste-water disposal wells. This will increase the number of counties on the earthquake interest list by more than double. About 10 new counties that are primarily in south-central Oklahoma have been added.

Last year, Oklahoma experienced 585 earthquakes of 3.0 magnitude or higher, more than in the past 35 years combined.