"Major earthquakes thousands of miles away can trigger reflex quakes in areas where fluids have been injected into the ground from fracking and other industrial operations, according to a study published in the journal Science on Thursday."
"Previous studies, covered in a recent Mother Jones feature from Michael Behar, have shown that injecting fluids into the ground can increase the seismicity of a region. This latest study shows that earthquakes can tip off smaller quakes in far-away areas where fluid has been pumped underground.
The scientists looked at three big quakes: the Tohuku-oki earthquake in Japan in 2011 (magnitude 9), the Maule in Chile in 201 (an 8.8 magnitude), and the Sumatra in Indonesia in 2012 (an 8.6). They found that, as much as 20 months later, those major quakes triggered smaller ones in places in the Midwestern US where fluids have been pumped underground for energy extraction."