(2) injection for disposal of waste water derived from energy technologies into the subsurface does pose some risk for induced seismicity, but very few events have been documented over the past several decades relative to the large number of disposal wells in operation.
Yes Virginia, there are a huge number of deep disposal wells, and very few earthquakes. I am mortified!
Forget everything you've read here. Forget rock mechanics and the fact there are only a very few 'sweet spots' for injection action. Oky-texy, continue with injection!
And Arkansas, stop fiddling with injection wells and closing them when there are a few earthquakes. :)