Can someone explain this EPA graph to me?
I'm not sure that this is in the appropriate forum, but here goes....
Here is the graph: http://www.epa.gov/japan2011/rert/radnet-sacramento-bg.html
When the EPA first published this data, they started at the point of the earthquake, which made the spikes in Sac look larger than what are currently there. I understand taking a wider view to get a better perspective.
However, I don't understand why the spikes were so large before, and suddenly, after the earthquake, they are so much smaller.
If I look across the country: http://www.epa.gov/japan2011/rert/radnet-data-map.html
I see that this occurs in many different places.
Any comments or insights?