As part of the NOVA team filming Japan's Killer Quake, I arrived in Japan two days after the March 11 earthquake and tsunami. I flew by helicopter over coastlines damaged by the event, consulted with colleagues at Japan's Earthquake Research Institute, and generally tried to gain a preliminary understanding of the nature and impact of the devastating 9.0 earthquake.

My first reactions on arrival in Tokyo were of admiration for the seismologists and earthquake engineering community of Japan. There was almost zero damage to the buildings of Tokyo, and, in fact, little shaking damage throughout much of Honshu, the largest island of Japan. This surely must be considered a success story given the enormity of the earthquake. It was the tsunami that did most of the damage, which I'll touch on below.

Here, illustrated with diagrams I have put together, are some initial thoughts, together with a brief discussion of potential dangers awaiting Japan as well as the U.S.:

Foreshocks and aftershocks



As this graph shows, several foreshocks (in red) occurred near the epicenter of the mainshock, but, regrettably, these were not recognized at the time as precursory to the mainshock sequence. As if the monster mainshock of March 11 were not enough of a scare, the Japanese people have endured numerous aftershocks, some of them larger than the Haiti earthquake. They continue to be felt now, two weeks after the mainshock.