There has been a change in the rate of the wastewater insertion in the disposable wells. A report has been published in Seismological Research Letters which states that this change in rate has added to the conditions that led to last year’s Pawnee earthquake in Oklahama.
The Pawnee earthquake was widely felt across Oklahama with the magnitude of 5.8. It is the largest earthquake recorded in the state since 1950’s. It has been suggested in the report that the Pawnee earthquake happened due to the active wastewater disposal wells. This is the possibly largest stimulated earthquake in the region so far.
Andrew Barbour of the U.S Geological Survey along with his team studied the new injection data. The study showed that there was a considerable increase in the insertion rates in the past few years that led to the Pawnee earthquake. The team also found that some wells were inserted wastewater at an even rate whereas some at an uneven rates. However, by and large the volume inserted was approximately the same between these two types of wells.
The author of the report states that “Long term injection may have been responsible for a gradual loading of the fault to the point where it primed the fault for failure triggered by the short term high rate injection”.