A leading seismologist has linked the process of shale gas fracking with more than 100 earthquakes that blighted a city in the US Midwest within the space of just 12 months. Since records began in 1776, the Ohio city of Youngstown had never experienced a single earthquake, until a deep injection well was built to pump waste-water produced by fracking in neighboring Pennsylvania. The Northstar 1 site started pumping operation in December 2010 and within the following 12 months seismometers in and around Youngstown recorded 109 earthquakes; the strongest being a magnitude 3.9 quake.