The UK's shale gas commissioner is resigning after just six months, saying fracking is being throttled by rules preventing mini earthquakes.Current government rules mean fracking must be suspended every time a 0.5 magnitude tremor is detected. But Natascha Engel said this cautious approach to earth tremors had created a de facto ban on fracking Report by Khanomh. Like us on Facebook at http://www.facebook.com/itn and follow us on Twitter at http://twitter.com/itn