What's the reason of earthquake cloud?

As a budding geophysicist, I must say that I heard this term only for the first time through you. A quick google explains why. Earthquake cloud is not generally accepted in the scientific community, though it is considered as a research topic. The first successful prediction of earthquake was in China, in 1622, through earthquake clouds, and most of the phenomenas that act as proof of this have happened in China, so that explains why you might have frequently heard about it. Till now there have been only ancient books and observations, but no concrete proofs or theory that explains it completely. It is also discussed in chapter 32 of Brihat Samhita, by Varahmihir, an Indian astronomer and mathematician. But don't worry, it's not a myth or superstition. Every revolutionizing theory that came up was first ridiculed. Coming to your first question: What is known now is that heat is produced due to friction in rocks during rupture, which can cause water in cracks and fissures to vapourize and form abnormal clouds. But scientists have not found evidence of sufficient heat before the earthquake. Another theory points to induced voltage, which indicates involvement of some electrical phenomena. The point is nothing's clear right now, and it will probably take a couple of decades before we get to any concrete theory to explain this phenomena. So to answer your second question: NO, it is not an accurate way to predict earthquake, yet! You might find more reading material here: http://earthquakeclouds.blogspot.in/ http://pinewooddesign.co.uk/2008/05/12/earthquake-cloud-prediction/