Scientist – August 19, 2013)
The Ohio quakes, centred around Youngstown, were triggered by the disposal of wastewater from fracking operations in the neighbouring state of Pennsylvania rather than by the fracking process itself.
The new geophysical research, by Won-Young Kim at Columbia University in Palisades, New York, is the latest to suggest that the main risk of earthquakes associated with fracking relates to the way the water used in the operations is disposed of afterwards. In Ohio, the wastewater was injected into a deep well.
This raised the pressure of water within the rock and triggered 109 small quakes between January 2011 and February 2012. The largest, on 31 December 2011, had a magnitude of 3.9.