An unexplained carpet of foamy bubbles filled streets in the centre of the southern Japanese city of Fukuoka in the early hours of Saturday morning shortly after tremors from a devastating earthquake of magnitude 7.3 shook the town. Twitter users posted pictures of the mysterious foam, with one calling it disgusting. I saw it just after the earthquake, said Kazuki Nabeta, who lives in the busy central district of Tenjin, where the bubbles were found. Some have speculated that the earthquake may have caused an underground pipe to burst. There was a fire engine there. There wasn’t anything special about it it was normal foam.