A self-proclaimed "earthquake information" website has a description here (Japanese) of the kinds of cloud formation you might expect to see before a major tremor. The science behind the claim appears to be murky at best and many people can't distinguish between aeroplane vapour trails and similar cloud types. However, this hasn't stopped Japanese netizens from uploading their own pictures of recent skies which seem to resemble the website's warning signs. Conspiracy theorists believe that the nation's leaders are aware of the imminent catastrophe and are making a point of staying away from the city centre - for instance, the Prime Minister has been visiting Korea.
