Itís no coincidence the number and magnitude of south-central Kansas earthquakes have dropped precipitously in the wake of reducing volumes of oil brine that can be injected back into deep formations.
Thatís because thereís little doubt about a link between earthquakes in areas close to high-capacity saltwater injection wells.
In fact, that connection has long been established, thanks to a 1989 earthquake in Rooks County, close to an injection well in whatís known as the Marcotte oil field in southwest Rooks County.
ďI donít think there was any question that this was related to saltwater disposal,Ē Palco Mayor Don Steeples said of the 1989 earthquake.
Steeples currently is on something of a sabbatical from his duties as Palco mayor, as heís been spending his days serving as the interim dean of arts and sciences at the University of Kansas. He originally retired from KU and moved back home to Palco, where he ultimately was elected as mayor on a write-in vote.
ďMy intention is to be back to Palco by Christmas,Ē Steeples said of ending his duties at KU, where he had long served previously as a seismologist teaching geology. He was on the team researching the cause of the Rooks County quake.
Rex Buchanan, interim director of the Kansas Geological Survey, also said thereís no question about the link between earthquakes and high-volume injection wells.
Thatís why the Kansas Corporation Commission in March issued an order reducing saltwater injection rates in portions of Harper and Sumner counties.
In the wake of that order, earthquake numbers have tumbled from a high of 24 in March to just six in August. As of this morning, there have been six in September.
One of those, was recorded at 11:04 p.m. Friday, 4 miles northwest of Plainville. It measured 2.6 on the Richter scale.
Buchanan said the number of bigger earthquakes has especially dropped off.
What isnít yet known, however, is just how much saltwater can be safely injected without triggering an earthquake.
Heís also uncertain what effect ó if any ó a dramatic decline in oil prices has had on oil production and, as a result, the amount of saltwater injected back underground.
What he is sure of is the risk of induced earthquakes remains.
ďI donít think thereís anybody here who believes the issue has gone away,Ē Buchanan said.
Thatís why he continues to strongly support the installation of a permanent earthquake monitoring network. That network eventually will include seismometers at Cedar Bluff, Glen Elder, Tuttle Creek and Fall River reservoirs, as well as Lake Meade and at Wichita State University.
For Steeples, heís seen evidence of a link between high volumes of saltwater being injected underground and earthquakes.
The amounts in south-central Kansas, he said, are sharply higher than what is seen in the Rooks, Ellis and Russell county area, and that might explain fewer earthquakes.
While Steeples said he thinks the smaller earthquakes will continue, heís not concerned an induced quake might have catastrophic consequences. Thatís because the earthquakes have been shallower and there arenít any big fault lines to move.
ďAre they going to set off a Richter magnitude 6 or 7 earthquake?Ē Steeples asked. ďNot likely because there arenít any faults down there long enough for that to happen.Ē