WARNING: SHALE GAS MAY TRIGGER EARTHQUAKES

Research has linked an earthquake (magnitude 3.9) that struck near Youngstow in Ohio, USA on 31 December 2011 to the underground injection of wastewater from fracking.

The practice of hydraulic fracturing, or fracking, involves injecting water, sand and other materials under high pressures into a well to fracture rock. This opens up fissures that help oil and natural gas flow out more freely. This process generates wastewater that is often pumped underground as well, in order to get rid of it.

A furious debate has erupted over the safety of the practice . Advocates claim fracking is a safe, economical source of clean energy, while critics argue that it can taint drinking water supplies, among other problems.

Scientists have known for decades that fracking and wastewater injection can trigger earthquakes, but earthquakes are not directly related to fracking of rock for natural gas, they  are due to injection of waste fluid from fracking. According to scientists future operators may look for earthquakes for about six months after the beginning of operations. However, there are cases when triggered earthquakes can occur nearly 10 years after the injection.