reply to post by r4winds
Hi r4winds. Welcome to the discussion.
Thanks for jumping in to answer r4wind's question while I had spaced out , NiteNGale2.
This thread needs more action, so I can find it on the
first page of this forum.
As I understand it r4winds, random tremor on the subduction interface, can be detected over a few hours, days or even a week or more, and not be
considered an ETS.
Not until there is GPS observed movement at the surface, is the jiggling considered a true episode. I believe the folks studying this phenomenon are
leaning toward renaming it "slow-slip"; putting more emphasis on the movement, and less on the tremors.
Have you read this good explaination of ETS from Central Washington
....and speaking of random tremor (that may not be so random); check out the last 2 weeks of action since the mid-Oregon episode was officially
Those few small detected bursts along the 20 km depth are inching oh-so-close to the locked portion of the CSZ.
Let's not forget that tremor are seismic signatures that:
occur at the plate interface as a direct result of the subducting plate grinding past
the overriding plate or they are spread out above the plate boundary possibly occurring on faults that are readjusting in response to stress changes
produced by the slow slip on the plate interface below.
(click the tremor FAQ link)
Tremor is picked up when those enormous plates are moving
, albeit rather slowly.
My next pic (which can be manufactured from the above link) shows the past 10 days of activity focused on southern Washington and northern Oregon. It
looks as if last month's ETS wasn't quite finished, and has decided to trek north.
If you click the past 3,6, and 12 hour links on the real-time
map, you can see it is still making
a nice push.
IDK, but to me it seems like major parts of the CSZ are "softening up" for some possible major movement. Of course, it could be another 120 years
off--we have such a short window of observation.
edit on 4/17/2013 by Olivine because: I need to learn to proof read before hitting the "post" button
edit on 4/17/2013 by
Olivine because: and I forgot the 2nd pic