There have been a few earthquakes along the CSZ during the past few weeks.
This
Mag 4.7 USGS at the far northern end of the zone. A tiny
Mag 2.7 USGS the same day, offshore Forks, WA. On 5 Jan 2012, a
Mag 3.2 USGS off the coast of Eureka, CA, and 7 small quakes
near Petrolia, CA. And let's not forget the 3 shakers
offshore of Oregon and southern Washington--
USGS Map
Nothing really big, but a lot of "rumbling". I did a search of Mag 3.5 and higher earthquakes during the past year, in the area. 64 total.
Not very many for such a huge geographical area, IMHO. There was one Mag 6.4 on 9 Sept 2011, three in the magnitude 5+ range (Mag 5.4 on 8 Feb 2011,
Mag 5.0 on 8 March 2011, and Mag 5.6 on 13 Oct 2011), and 43 magnitude 4.0 to 4.9.
I also looked at the tremor maps. Here is a look at the episodic tremor and slip over the past year. The brightest areas indicate the most slip. And
a pic of the surmized locked portion of the CSZ, for reference.

Here is the past month of slip; blue is oldest, red is most recent.
All of these relatively small earthquakes, along with the swarm at Mt. Rainier, are making me take notice. This is the list of Mag 7.0 and higher
earthquakes in the same area, since 1976. Nothing since 2005...
PDE 1980 11 08 102734 41.12 -124.25 19 7.2 Mw01023 7C. .......
PDE 1991 08 17 221714.68 41.82 -125.40 13 7.0 MwHRV 5FM .......
PDE 1992 04 25 180604.21 40.37 -124.32 15 7.2 MwHRV 8CM .T....S
PDE 1994 09 01 151553.08 40.40 -125.68 10 7.0 MwGS 6DM .T.....
PDE 2005 06 15 025054.19 41.29 -125.95 16 7.2 MwHRV 4FM .T.....
Source of external data
I'm certainly not trying to fearmonger, just sharing what I see.
Just wanted to add a quote by one of the seismoligists at UW, listed under his current research, to show why some people think the tremor and slip
might be important:
One paper of mine is coming out momentarily in G-cubed, showing that tremor can trigger earthquakes, at least starting to
address the important question of whether the 500-year M9 in Cascadia is likely to be set off during a tremor episode.
Source of quoted text
edit on 1/16/2012 by Olivine because: linky
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