What might be happening at Mt. Rainier?

Eruptions reader Doug pointed out in a recent comment that the seismicity at Mt. Rainier in Washington has increased over the last month or so. Take a look for yourself:

Mt. Rainier seismicity over the last year (8/2008 to 9/2009). Image courtesy of PNSN

Taking a closer look, over the last week there has been 7 earthquakes over the last 5 days – all between M1-3 – near Rainier, most calculated to be between 1.5 to 5.8 km depth.

Any thoughts? I see a lot more noise (earthquakes) between 3-6 km depth. It could as benign as seismicity due to fluid in the extensive hydrothermal system at Rainier or it might be magma moving up a level in the magma conduit … Interesting stuff to say the least …