PBS News Weekend 
Season 4, Episode 62 of 99
On Sunday, NewsHour's Stephen Fee reports on the growth of earthquakes in Oklahoma over the past six years. In 2015, the state experienced more than 900 magnitude 3 or higher quakes, compared to just 109 events two years earlier, in a phenomenon that took off in 2009. Scientists have tied the sharp increase in the intensity and frequency of quakes to underground wastewater injections related to oil and gas drilling, which includes fracking and horizontal drilling. Now, the quakes have led to calls to toughen regulations on drilling in order to reduce seismic activity, while the energy industry is challenging the science.
