It appears that operations of Orkuveita Reykjavíkur are creating the earthquake swarms that have been seen in Hengill volcanoo. But as part of operations in Hengill geothermal plant they pump down cold water into the bed rock under considerable pressure. This is according to Sigþrúður Ármannsdóttir a geologist at Icelandic Met Office.
It would appear that yet another one pumping water under pressure is evidently causing earthquakes. Whilst Arkansas is not sitting on an active volcano 🙂 it still illustrates the point that pressure injection and earthquakes go hand in hand.