ETS Event of Spring 2018
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Blog for ETS of Spring 2018
Deep Tremor News: March - . 2018
This BLOG-like page is being generated in a form similar to previous ETS ones to document and provide information on a Northern Washington ETS that should start sometime between April and May, 2018. There are no special experiments in the field for this ETS. We will be tracking and reporting on this ETS using data only from the real-time regional networks (UW, UO, CN, TA, PB, CA) and/or information reported to us by others.
Produced by Steve Malone, PNSN Professor Emeritus
Start: May 8, 2018 pause started May 23
Information will be posted on this page (latest at the bottom) and references to figures from time to time.
NEWS (latest is at the bottom):
March 23, 2018 - The next expected main Washington - British Columbia ETS should start sometime in April or May based on the roughly 14 month repeat period observed since around 2000. The previous one started on Feb 18, 2017 and ended on April 6 but had a two week hiatus in the middle. I am not sure if the extended "start-stop-start" nature of the last ETS will make any difference in the start time for the next but I will stick my neck out and say it will start before June 1, 2018.
In the meantime to make sure the wech-o-meter is ready we have gone through all the configurations to make sure that the best combination of working stations are being used. We are ready! Let err rip.
May 12, 2018 - I usually wait for a full week of tremor before declaring the start of an ETS. However, so many of my previous predictions of what would happen have been wrong. I am used to it and so will take a chance and declare this ETS started as of May 8, 2018, after only four days of tremor. This one seems to be classic, starting only slightly north of where many in the past have started. There appears to be a subtle migration up dip, which is typical, and it is pretty close to right on schedule. Thus I am assuming we are off and running. It is way too early for any obvious geodetic signal to have started but will keep an eye on the typical set of stations to see when that signal can be spotted. Stay tuned.
May 19, 2018 - We are now 10+ days into this ETS and it seems to be developing similar to many of the previous events, particularly those from 2007 - 2011. Over the past couple of days tremor first spread slightly to the north and then to the south. Here is a snapshot of the first 10 days of this ETS color coded by time (blue early, red late).
Be aware that the early (blue to yellow) events south of Olympia are probably due to glitches in the data and are not real tremor locations. We have since reconfigured the system to not use the glitchy stations causing these false locations. We expect this ETS to continue for at least another two to three weeks spreading a bit farther south but quite a bit more to the north. Thus far I (a seismologist) don't see any evidence of geodetic slip in the GPS data provided by PANGA. You can looked for yourself at the Central Washington University PANGA web page.
May 29, 2018 - Me and my big mouth. No sooner had I predicted what would happen then the whole thing sputtered out. The last day of obvious ETS-like tremor took place on May 23. There were a few minor events located on May 25 in the south Puget Sound but nothing like what would be expected for a full blown ETS. Maybe it is just a pause. Maybe this one is a dud. Maybe the world will come to an end. Who knows at this point. One thing is for sure. ETS patterns have some very general things that seem to be predictable but in detail they are all over the place. I will not even try to predict what might happen next. OK, yes I will. I think that within a week it will start up again somewhere, likely in the northern Olympics but it could be in South Puget Sound or up on Vancouver Island or no where at all. Yep, some prediction. Oh well.
For those of you who have been watching the wech-o-meter in detail you are probably saying things like "Oh my gosh, the northern end of Vancouver Island is going to fall off". Nope, the strange line of events showing up on the past few day's plots heading north-east onto the mainland are total artifacts of some telemetry glitches coming from 4 Canadian seismic stations. Starting on May 25 it seems there are LOTS of gaps from these stations for an unknown reason. These gaps conspire to fool the wech-o-meter into thinking there are bursts of tremor taking place here. Looking at the original data it is obvious that is not the case. We are working with the Canadian seismic network people to try and get this fixed. However, we will remove these totally bogus events from our tremor catalog so as to not confuse people.... and ourselves when we look at it in the future and forget that it is just garbage. Thus, at the risk of providing fodder to the whack-o conspiracy theorists using this as proof that aliens from planet zeeoxeon have abducted tremor events, we will fess up right here and now that we be the aliens and have deleted, removed, terminated said offensive garbage from our catalog. We will also be removing the offending Canadian stations from our wech-o-meter configurations until they get fixed.
June 21, 2018 - What a strange ETS! Of course, because I said that it would restart back in late May the area stayed ridiculously quiet up until a few days ago. Other than some down-dip pipsqueaks on May 31 and June 14 there have been virtually no tremor locations in northern Cascadia for most of a month. This is not the way a traditional ETS should go. But, why stick with tradition? On June 18 typical ETS type tremor started up again in south-central Vancouver Island. Maybe this is finally the continuation of the standard ETS. But maybe it is a separate one that will now head north. It is filling in nicely today. Thus, while I have been warned many time to not declare a real ETS underway until there is at least a week to 10 days of solid tremor I am going to throw caution to the wind and say "it is going again.... or some more".
Perhaps I could be talked into calling this "restart" a "separate" ETS. For several ETS events in a row activity stretched from central Vancouver Island to southern Puget Sound, sometimes progressing north, sometimes south and sometimes jumping around a bit. The last ETS ran for a while in Puget Sound and then took a two week break after which it continued on Vancouver Island. The one this year seems to be doing sort of the same but with a four week break. Is there a pattern here? Is the standard cross-border ETS now be breaking into two separate ones unrelated to each other? Can we blame this fracturing of the cooperative US-Canadian ETS events of the past on the fracturing political cooperation or, perhaps the other way around. I will wait to see what additional surprises are thrown our way before delving more deeply into cause and effect.