Okay, regarding the intervals of ETS and possible influences of very large quakes (ie Mw approx 9), there is some good data of some previous years in
the old ETS blogs, but I (or someone else) will need to go through it.
Here's the link to ETS blog reports for 2003-2009 inclusive
Crucially to Anmarie's comments, the nearest PNW ETS event following the Dec 2004 Asia quake was from Sept 6 to Sept 30, 2005. In 2004, however, there
periods of ETS in the PNW, from May 3-18 (Sth Puget Sound Tremor) and July 8-24 (Nth Puget Sound Tremor) -- meaning in the months
the Asia quake.
Now, while there is possibly no causal link between those two 2004 events and the megathrust quake off Banda Aceh, it cannot be stated categorically
that they are completely unconnected.
However, the ETS of Sept 2005 followed about 14 months after the second ETS of 2004 (in July), and this, at least, is in line with what has been
observed as the "norm": according to the PNSN people, ETS events typically seem to occur about 14 months apart. So, in that case, it doesn't seem that
the big Asia quake had any significant or measurable effect on the start of the next ETS in the PNW.
Now, here's something I hadn't been aware of. I don't know if any of you know this already so my apologies if you do, but in the
Reports for the 2004 ETS events
June 4, 2004 - TWO NEW DEVELOPMENTS: 1. The deep tremor in the Pacific Northwest seems to have died out completely. 2. We have found deep
tremor in northern California. After the southwestern Washington deep tremor became weak and seemed to move into northwestern Oregon it became
even weaker and died out with the last period of obvious tremor being on the night of May 27. Nothing recognizable as deep tremor has been seen since
then. However, with prompting from Seth Moran of the Cascade Volcano Observatory and the help of David Oppenheimer of the Northern California Seismic
Network we started examining data from northern California and see deep tremor there. Starting weakly on about May 23 with very strong bursts from
time to time from May 25-29 we are still seeing small to medium size bursts from time to time today. Some of the stronger bursts could be located and
are shown on a map of northern California. The colors are for events on
different days (May 25,26-red, 27-yellow, 28-green, 29-blue). There is no reasonable depth control for these events yet.
(Bolding mine. I have also encoded the live link to the relevant map.)
I think this is of some significance. I repeat, I'm not sure if you all knew about this already, but if not, here's what I'm thinking: while we
sometimes see tremors on the PNSN maps that extend (even in clusters) into Nth Cal, they are not the same as ETS. They are mainly microseismic events
but not of an ETS character.
So, if they were already observing ETS in Nthn California seven years ago, surely this just adds more weight to the hypothesis that the subduction
"line" could extend much further south than currently surmised? Westcoast holds that opinion and I humbly agree, but here's the main point: shouldn't
they be doing similar array studies even further south into Cal to see if there is similar ETS? I mean, much
If it can be confirmed that there is ETS well into SoCal, then this data would have to impact the current theories of how the various regions
I'd like to write more but I'm losing coherence I think. Just too tired to think straight. Happens. Hope you follow all this.
edit on 3/10/11 by JustMike because: I think I added something.