Claire Pontbriand

For anyone following the rapid increase in the frequency of earthquakes in Oklahoma attributed to the injection of oil extraction wastewater deep into the ground, the story just took a couple of interesting turns.

Over the past seven years, regions with historically low seismicity in the central U.S. have seen a remarkable increase in the frequency of earthquakes thanks to human activity.

Big earthquakes (or mainshocks, as seismologists call them) get lots of attention, and with good reason: they happen suddenly, often without warning; they almost invariably cause the greatest damage and the greatest loss of life; and by definition they have the largest magnitude.

Over fifty years ago not only a major turning point toward a better understanding of earthquakes occurred, but also the large-scale motions of Earth's lithosphere. Read on.