This is one which I found around the Internet, and I apologize if you know anyone affected.
Lets start at the very beginning. During the second world war the US military was testing new forms of warfare. In '44 and '45 they detonated mini Nuclear bombs of the coast of New Zealand in an attempt to create a 'tidal warfare' of some sorts. Anyway theory goes that bombs going off, if they have a certain amount of power, could cause earthquakes and tidal waves. As you can guess people claim that eco-terrorists set off a bomb near Sumatra to cause the earthquake. The power needed to cause such an quake would need to be colossal so I doubt that no side effects would have occurred that have not been yet noticed. Another theory is the use of electromagnetic waves being used to set off natural disasters. In '97 defence secretary William S. Cohen did say that: "Others are engaging even in an eco-type of terrorism whereby they can alter the climate, set off earthquakes, volcanoes remotely through the use of electromagnetic waves. So there are plenty of ingenious minds out there that are at work finding ways in which they can wreak terror upon other nations. It's real, and that's the reason why we have to intensify our efforts, and that's why this is so important." To be honest I sincerely doubt the credibility of this theory and the seriousness of whoever cam up with it.