Cannikin (5 Megaton Nuclear Device Amchitka, Alaska). Excerpt from "Atomic Journeys: Welcome to Ground Zero". Mind you, the footage is directly above the epicenter, whereas the epicenter of most earthquakes (like the one in Japan) are like a mile or more below the ground and a few miles off-shore. (Don't quote me on that, though). I don't recall how deep this one was buried, but I think 1-2 miles is about right. (Don't quote me on that either!).