[aBootes]

Hey Rustbucket,

Can you give a quick explanation for the different colors on that map? And perhaps for the significance of larger earthquakes at shallower levels?

Thanks...

[rustbucket]

The red circles were earthquakes in the last month. The green circles were earthquakes within the last year but more than a month ago. As you surmised, the larger circles represented the larger earthquakes. A lot of the larger ones were in the 3.0 range.

The plot came from the following site.

http://www.geophys.washington.edu/SEIS/PNSN/HELENS/

Here's an aerial plot of the same data. Same color code. There seem to be a fair number of old magnitude 2 and 3 quakes on the side slopes of the mountain. I don't know why these larger quakes are there. Bigfoot maybe.