Yes Virginia (ironic, no?), there is a limit to the size of an induced earthquake.
The magnitude-5.6 quake that rocked Oklahoma three miles underground had the power of 3,800 tons of TNT, which is nearly 2,000 times stronger than the 1995 Oklahoma City bombing.
The typical energy released in tremors triggered by fracking, "is the equivalent to a gallon of milk falling off the kitchen counter," said Stanford University geophysicist Mark Zoback.
Zoback is the really, really big star of the earthquake academic world. I'm surprised he gave a sound-bite.
But wastewater from hundreds of wells is often collected and disposed of deep underground through so-called injection wells. In Lincoln County, Okla., where the recent earthquakes hit, there are approximately 1,982 active oil and gas wells, according to Matt Skinner, spokesman for the state agency that oversees oil and gas production. There are 181 injection wells.
I was suspecting there was one deep injection well! Oh well, (ha!), let's wait for the next one.....