Interesting idea.
Earthquake is caused by build up of pressure between two bodies of rock. They eventually release, sometimes with catastrophic results. Maybe try repeating the earthquake trigger on a regular date. Regular triggers could prevent the big build up.

It would be interesting if we had the ability to detect a quake will probably occur along a particular fault near a populated area like Los Angeles within the next few decade. Imagine we had the technology to cause the earthquake at a time of our choosing. Would we do it? We could give everyone ample warning to secure objects, get outside, or even get out of town if they wanted. It would be odd, though, to pull the trigger knowing the earthquake might catch someone unprepared.

BTW, I have no idea if human activities can cause earthquakes; just an interesting thought experiment.