When I was taught statistics, this was regularly brought up as a big no-no in science. However, I read a guide to practical statistics that had a gem about predicting the stock market. If we discovered surges in the market correlated to newspaper sales, we wouldn't discard this as look-elsewhere. In fact, we'd follow newspaper sales very closely.

Predicting earthquakes has a big upside for humanity. If there is even a small correlation -- even if we don't yet understand it -- we can benefit from it.