Contributing writer Michael Behar has an intriguing feature today that details the science behind the link between injection wells and earthquakes. For a visual rundown of the fascinating process, check out the GIF below.
Drillers inject high-pressure fluids into a hydraulic fracturing well, making slight fissures in the shale that release natural gas. The resulting briny wastewater flows back up to the surface, where it is transported by truck or pipeline to nearby injection wells. The liquid is then pumped down the injection wells to a layer of deep, porous rock, often sandstone. Once there, it can flow in every direction, including into and around faults. Added pressure and lubrication can cause normally stable faults to slip, unleashing earthquakes.
Illustration: Leanne Kroll. Animation: Brett Brownell