@MarianSteinbach has done a good job putting together a collaborative effort on the tracking of radiation levels at various sites across Japan. She has also created a chart of the two closest measurement points to the distraught reactors. This chart was able to identify the fact that some new development was occurring at the reactor at some time before the announcement that there was a new fire at the plant. @makiwi identified this on his tweet and alerted his followers.
I have taken a look at this chart and see something interesting. The data in this chart doesn't go back far enough (seems @MarianSteinbach had to delete the old data to make it manageable against vandals). However, before the first fire broke out on 4 and the reactor blast at 2, the levels were much lower.
Now we can see after this second fire at reactor 4 that the radiation levels seem to be settling out at a much higher (~1800nG/hr) level. Any theories as to why this is occurring? *Edit* seems to have settled out.
Updated: 17:20 PDT Included older data. Also, Seems levels are dropping quickly now. Also note that this is an interactive chart... So it's being updated from the time it was originally posted.
Updated: 17:24 PDT Included image in case doc goes down.
Updated: 18:02 PDT Note that these levels are well below that which people should be concerned about.
Updated: 22:57 PDT Add URL for source data. I have been tracking this against the actual site and it's accurate.
Updated: 16/3/11 13:59 PDT Updated with more prefectures.
Japan Radiation Data History
Disaster Prevention and Nuclear Saftey Network for Nuclear Environment