Trishntek wrote:ya mean if i place my full coffee cup on top of my cookie it is more likely to break than if i place my empty cup on it?
Note to self, must not make "cookie" joke.
Now, back to earthquakes.
Imagine a large spring, held compressed by a small piece of metal. Imagine that there is a ratchet that is used at random intervals to compress the spring even further. Just before the point where the piece of metal would break, a fly comes along and lands on it, ever so slightly disturbing the system. BANG! The metal breaks, the spring expands, and the fly is vaporized.
So, the question is, did the fly cause the spring to go off? It depends on what you mean by "cause."
There are a lot of effects that are correlated with quakes, including other quakes. Sometimes you can make a plausible case for enough energy being added to the system to trigger a quake, and sometimes you can't. The
1975 Oroville dam quake is considered to be a case where the weight of the water and the lubrication from the water very likely contributed to the quake. But the stress and the fault system had to be there first, and that's where the energy comes from.
The
slow tidal pull from the moon can raise the chance of quakes, and even
some volcanic eruptions.