There’s been some adjustment going on just about daily for a month or so in a long line running up the Washington coast: I don’t know the fault maps well enough to say exactly which faults are active, but there was a larger one, around 4, recently, somewhere up near Vancouver BC (you could about pin them between Vancouver WA, right near the Oregon border, and Vancouver BC, up in Canada) and another series in the strait near Seattle…and, southward. While St Helens itself has microquakes nearly daily and has had for years since its last dome-building, this is the biggest quake closely associated with the mountain that’s happened in some few years. It apparently was centered under Spirit Lake, which you may recall from the big-eruption side blow-out footage. Interesting to watch one of the more active tectonic processes in the States: St Helens will rebuild itself: it’s far from finished. And while this may be a response of the fault system to stress of the moving plates, this could also provide a nudge to St Helens and an influx of magma.
4.3 at 9 miles from St Helens summit…with aftershock.
by CJ | Feb 15, 2011 | Journal | 11 comments
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ooooh! how far away from that are you?
Oh, about a 3-4 hour drive. Say from the big eruption, we have a 4″ ash layer in the lawn (we found it when excavating for the koi pond)—but Spokane is pretty safe. From Ritzville, 100 miles from here, they were taking ash away in dump truck loads. And even this far, the sky went to night.
I procrastinated and didn’t get to see it during the dome building episode, so if it flares up again, Jane and I will certainly take a drive to go see it—not in any explosive phase, to be sure; but geologists have learned a lot from this volcano, enough to be able to say with some tentative confidence (how’s that for an oxymoron?) that a series of ‘harmonic tremors’ represent magma on the rise, and if that sets up, no tourists! If it’s not doing that, it’s ‘safe’ to go view at a respectful distance. Tours go into the blast zone, showing people how the land recovers, how plants regrow, etc, but they won’t go if they get harmonics going on.
This info has been useful in Mexico and southward, advising locals with some degree of accuracy when it’s time to evacuate, and they’re getting more confident in doing so. This is very important to people with crops and livestock that can’t be left untended indefinitely: if you can tell them, “We’re pretty sure, and this is why we’re pretty sure,” they’ll obey an evacuation order, understanding at that point the safe bet is to clear out for a little while, planning to come back, or for one person to come back periodically and then get the hell out by nightfall, closely advised by a team of geologists, “Yeah, it’s no worse than it was, but don’t linger.” This way they’re not asked to leave their land for prolonged periods on a mere guess something could happen.
4″ ash would kill your lawn – and your koi, I should think, wouldn’t it?
it wouldn’t be good. We’d probably add a circulation pump and wade in and try to catch them to bring them all into a trash-can makeshift tank in the basement, with heavy aeration until we could get their pond reamed out. As for a lawn, the last ashfall pretty well did kill the lawn, which is why we have now ripped out all lawn in favor of trees and mulch.
The USGS Survey Maps for earthquakes are very useful for tracking activity. I have the site bookmarked for my state. In the meantime, here’s a link to the Mount St. Helen’s quake:
http://earthquake.usgs.gov/earthquakes/recenteqsus/Maps/US2/45.47.-123.-121.php
Looks like one in the Wasatch Corridor of UT, Northern CA had two, Southern CA had two, then there were two recorded at MSH, as well as the Vancouver. What’s strange is Arkansas also had a quake, which I believe might be related to the New Madrid Fault. I live on a branch of the New Madrid Fault, and my county is the most seismically active county in Ohio. Earthquake Central is about 11 miles up the road. I’ve been in several good-sized earthquakes while stationed on Guam, so I’m aware of the unreal feeling they can give, especially if they’re in the middle of the night and they wake you up. (BTDTGTTS)
One thinks about the very large caldera to your southeast, and while the region is very beautiful, it’s living on borrowed time according to geologists.
As for the major faults along the West Coast, I hope that any adjustments are slight, and do not involve the sudden release of petatons of rock in a northwesterly direction for a distance of 2 or 3 feet.
and now this on top of it!
[url] http://news.yahoo.com/s/afp/20110217/sc_afp/usastronomytelecomnasachina [/url]
and on top of all that, a very large CME from the southern hemisphere of the sun, which has already affected communications in China. I’m waiting for it to wipe out my ham radio communications, too, but even if it does, I won’t notice, since I don’t have any HF radios operating right now.
I read in a book about Oregon geology that this fault starts in a graben [sunken valley] in Eastern Oregon and continues in an arc through Southwest Washington and up to Vancouver Island. It’s caused by a portion of the plate butting up to the northern and eastern boudaries of the fault that is rotating clockwise against the rest of the North American plate. This causes the eastern end to sink and most of the rest of the fault is slipping sideways. This is the fault system that caused the magnitude 6.8 Nisqually quake centered in the South Sound in 2001. I’ll tell you what, that was vintage rock andd roll!
Yeah! First earthquake I ever felt! We had them in Oklahoma, but I couldn’t tell them from the atomic cannon at Sill, which had much the same effect as a 2.3.
Yep, if Yellowstone goes, we’re headed for the coast. If the coast goes, we’re sitting pat. And if the old field to our south goes, well, it’s the coast again. Our 4.4 here in Spokane didn’t produce quite the adrenaline rush of staring down the barrel of an oncoming tornado—but they are definitely exciting. And I DON’T want to see Yellowstone wake up. I have somewhat of a suspicion it’s migrated a bit, that the hottest of the hot spot is beyond the caldera rim, in its general direction of progress, but I wouldn’t bet anything on it.
Guam was an interesting place to experience earthquakes. My first time was during a typhoon. I had the house all shuttered up, was sitting in the living room reading (my wife had been called in to work) and I heard what sounded like a freight train coming. I thought to myself that this was not an area that gets tornadoes, and then my chair was jerked very hard to one side and then back again. Kind of like someone had snapped a rope and the wave traveled along the rope. Woke up another time to a 4.7, my water glass was tapping against the lamp on the nightstand and the bed was moving sideways. My wife never woke up. Can’t say what the strongest I’ve ever been through, but I’d guess that was probably it.