Why is this not surprising? Earthquakes are apparently caused by pressures building up under the earth’s surface. Fraking builds up pressures under the earth’s surface.
Michael Wines at the NYT writes: “Wells for fracking are typically sunk horizontally into thin bands of shale deep beneath the surface, and a soup of water, chemicals and sand is injected under intense pressure to fracture the rock and release trapped oil and gas.
The Poland Township study concluded that only two of the seven wells, with segments closest to the fault, were inducing the earthquakes. “It seems that only the segments that were within about a thousand yards from where the fault was produced earthquakes,” Michael R. Brudzinski, a professor and seismologist at Miami University in Oxford, Ohio, said in a telephone interview.”