So, with Japan in the news today, weird theories about earthquakes are at the forefront again. The theory that solar flares are correlated with earthquakes came up, so of course I tried to find some information online. To my surprise there seems to be quite a bit. Does this appear to be credible research?
NASA data would indicate that there is no causal relationship. With the sheer number of earthquakes that are happening on the earth on a daily basis, there is absolutely a correlation in time between any solar flare and the earthquake itself (just like the clustering illusion), thus people will tend to commit the post hoc ergo propter hoc fallacy. However, the causal relation ship is not established, and would seem to be tenuous at best. Considering the very disparate causes and mechanisms related to each phenomenon, the link is very unlikely.
Some additional information: Along with solar flares, there is speculation about the "super moon" causing the earthquake in Japan. This is also easily debunked.
EDIT: A geologist associate of mine also has this to say about the earthquake in Japan. Some good info in layman terms I think.