ETS Event of Summer 2024

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Blog for ETS of Summer 2024 

This BLOG-like page is being generated in a form similar to previous ETS ones to document and provide information on a Northern Washington - Southern Vancouver Island (NW-VI) ETS.  The UW has no special experiments in the field for this ETS; however other groups may have interesting observations that can be reported here if authorized. We will be tracking and reporting on this ETS using data only from the real-time regional networks (UW, UO, CN, PB, CA) and/or information reported to us by others.

Produced by Steve Malone, PNSN Professor Emeritus

ETS dates:  

Start:  Aug 6, 2024 - END:  Sep 6, 2024 (Southern Vancouver - Northern Washington section)

NEWS (latest is at the bottom):

Jan 16, 2025 - Oh dear.  It has been a year since I posted anything about tremor here.  Lots of excuses regarding injuries, trips, other activities but mostly just that I am retired and a bit of a flake.  But finally I am going to summarize very briefly observations for the “main” tremor region of Southern Vancouver Island to south central Washington.  While other parts of Cascadia have bursts of tremor associated with slow-slip these blog pages have mostly just covered this “main” area because…… well, it was first noticed here and it is close to home and has the longest good record and has had a number of special studies and…. I have no other reasons or excuses. I can not promise I will not be equally lax in writing up tremor observations in the future, but maybe some other tremor hot-shot will take over for me… sooner or later.

 

OK, the story in short the way I see it is that the main part of this region had a “normal” tremor sequence of about a month, August 6 - September 6, 2024 (see map below). This was about 16 months after the roughly same area went from April 4 to April 25, 2023 but just over 12 months from the last lower-level sequence in south Puget Sound that was July 15 - August 4, 2023.  See previous blog for details of that complicated set of sequences.

 

Below is a timeline showing tremor activity in the area from central Vancouver Island to Southern Washington for the whole years of 2023 and 2024.  I have marked with colored bars the sections for what one might call individual  ETS-like tremor sequences. 

Note that there are very short bursts of tremor out side of the marked time periods.  These are typical of inter-ETS tremor and are usually located slightly down-dip (to the east) of the main sequences. The times marked with the red bars are the times of tremor events falling in the main ETS sequences that have been clearly related to significant slow-slip in the past. from southern Vancouver Island to southern Puget Sound.  There are three sequences marked with blue bars that correspond to sequences north of the main sequence (central Vancouver Island) and the one green bar marks the time of a sequence clearly south of the main zone (south Washington). There is one very short sequence of only one week (grey bar) whose tremor locations are in the central Puget Sound and thus might be considered a very short or truncated main ETS; however, most its locations are spread out to the east of the normal main group so could just as easily be an extended down-dip, inter-ETS sequence.

 

As I outlined in the previous blog in 2023, the complexity that seems to be developing then may have just been the different parts of this region lighting up nearly at the same time.  Since they are on slightly different inter-event intervals that is bound to occur.  Maybe they are again separating so each part is clearly its own thing.  Of course all of this is just speculative blabber and has little scientific significance….. that I can tell.

 

Just to satisfy everyones need to see a map I include below a color coded by time map of the main sequence that we hope is back on a roughly 14 to 15 month schedule.  Note that it nicely progresses from north to south.  The next one of these should occur this coming fall.  I’ll try not to be so remiss in blogging about it when it comes.