We “Ask an Expert,” Columbia University’s Heather Savage, about fracking and its relation to earthquakes in the United States. She explains that any fault in the earth at depth is under stress. It’s under stress from the weight of the rocks above it, and it’s also under stress from tectonic stresses in the crust. When we’re fracking, we’re ingesting pressurized fluid underground. We’re doing this in order to actually make cracks in the rock of interest in order to get the gas out. However, during your fracking operation, if you intersect a pre-existing fault, that pressurized fluid can find that fault and un-pin it just a little bit and allow an earthquake to occur.