We've heard the reports and told the stories of Japan, how it's facing its worst crisis since World War II, about a death toll in the tens of thousands, the massive destruction of entire cities, and continuing threats of nuclear meltdown.  Now, here's more terrifying news: The threat of earthquakes hasn't gone away –  it has increased.  Thomas Jordan is the Director of the Southern California Earthquake Center. And his work shows that Japan is under an increased threat for aftershocks. He appears in a new NOVA special "Japan's Killer Quake," which premiers tonight on PBS.  Collum Macrae is one of the producers of the documentary.