Looking at Netc sites in Hokkaido (northern island), there seems to be a correlated spike of radiation (~50% rise) lasting about 4 hours at all sites on the island, starting at the north end on Aug 4 evening, then 2 sites further south on Aug 5, and the other southern sites on Aug 6. This seems like a real environmental event due to the correlation. As for the source, if it's not natural there are no nuclear sites on the island, so maybe the source is further north, such as the Russian naval base Zavety Ilyicha where they decommission nuclear subs and suffer unreliable power and labour issues. Nothing on that site showing on Google though (yet...).

Thanks for the tip. I need to go look at those graphs. Feel free to post the station links to make finding them easier for subscription members. Thanks again!

Here is the first site: http://netc.com/chart/view.php?n=6%3A01000-0106.
It's the northern-most Netc site in Japan, and all the sites on the island show the spike. If anyone looks at if after Aug 11, you will have to pull down the 2 week or longer chart.

Had another look today, there's a similar wave of high readings crossing the southern island right now.

Looking back on the history charts of Nagasaki (one of the Radcon-4 sites), there was an even bigger spike on June 30:


In fact all the sites here seem to show it. I sure hope these events are being traced by local scientists.

Nice catch, thank you.

My wife has a friend who took her family to Hawaii and has been posting pictures on Facebook of the family in the Ocean off the beach. Some people will just not listen. We can post a cat picture or funny video on Facebook and everyone hits "LIKE" but post anything about Fukushima or radiation and everyone is silent.

Make sure you select the "FULL" Japan maps, it is not selected by default.