The following are links that are useful in helping to understand the earthquake that struck Japan on March 11 and the consequences it had on the Fukushima nuclear plant.
With specific regards to the earthquake itself, the Japan Meteorological Agency provides this animated map showing that there was not just one massive quake but hundreds of tremors. The first, of magnitude 5.2 came at 01:54 JST (local time). There were two more smaller tremors before the main, magnitude 9 earthquake struck at 14:46 JST. There has been an almost constant string of aftershocks ever since.
The explosions at the Fukushima nuclear plant are being logged and updated both by the International Atomic Energy Agency on its website as well as on the Japan Atomic Industrial Forum’s site accident update log.
To understand and put in context the threat to health posed by radiation, here is a comparative radiation dose chart . It shows the radiation exposure levels of simple activity like sleeping next to somebody or eating a banana to extreme circumstances such as the exposure levels in the immediate aftermath of the Chernobyl disaster.