According to the Secretary of former Japanese Prime Minister Naoto Kan, the ground beneath Unit 4 has already sunk by about 31.5 inches since the disaster, and this sinking has taken place unevenly. If the ground continues to sink, which it is expected to, or if another earthquake of even as low as a magnitude six occurs in the region, the entire structure could collapse, which would fully drain the cooling pool and cause a catastrophic meltdown.
"If Unit 4 collapses, the worse case scenario will be a meltdown, and a resultant fire in the atmosphere. That will be the most unprecedented crisis that man has ever experienced. Nobody will be able to approach the plants . as all will have melted down and caused a big fire," said Murata during the interview. "Many scientists say if Unit 4 collapses, not only will Japan lie in ruin, but the entire world will also face serious damages." http://fukushimaupdate.com/ground-under-fukushima-unit-4-sinking-structure-on-verge-of-complete-collapse/