[TommyDale]

"Could an earthquake be purposefully triggered by, say, a deep underground nuke in the fault area?"

I would think that might not be a wise experiment. One of the most devastating earthquakes in recent years was in the small town of Coalinga. The earth dropped, rather than shook, and they think it might have been from pumping so much oil from under the area, causing a cavern.

[Dog Gone]

they think it might have been from pumping so much oil from under the area, causing a cavern.

That's absurd. Oil isn't an underground lake. It's contained in solid rock.