Magnitude 3. Big deal. That's what happens when you break rocks -- they shake around a bit. In fact, I'd say gas fracking
is earthquakes -- you characterize what you're doing underground using a seismometer and picking up the vibrations.
Saying "but if fracking can cause small earthquakes, might it not one day cause a large one" is a bit like saying "if your cat can devour a mouse, how do we know it won't one day devour an entire city?"
