“If you inject about 10,000 cubic metres, then the maximum sized earthquake would be about a magnitude 3.3,” says McGarr. Every time the volume of water doubles, the maximum magnitude of any quake rises by roughly 0.4. “The earthquakes may end up being much smaller, but you want to be prepared for the worst-case scenario,” says McGarr. The relationship is straightforward, but it is the first time that anyone has quantified it, he adds.
Ah, if you dig at the toe of a mountain slope, the maximum landslide is the same size as the road cut. This would be a good rule most of the time. Lots of people have died because you can trigger an absolutely monstrous landslide. I have no more comments on this.