Well, the crisis is... mitigated now. I'm getting the new seismograms again for now; we'll see if it sticks. You may notice the images look smaller now. Because they are. These "new" seismograms of theirs show 220% less detail than the old ones did (659 pixels to show 1800 seconds of data, or 2.731 seconds per pixel, whereas the old ones showed 1.25 seconds per pixel). So you can really forget about seeing harmonic tremors on them now. Also note that the live seismograms always show 24 hours into the past, which can be misleading on the ol' Compare-O-Graph. Today's will show the live ones; previous days' will show the midnight-to-midnight ones.
It also seems that they aren't archiving seismograms for certain seismometers, so my archived copy of them will always have a little missing time at the end. Those are: B208, B944, B950, FLWY, H17A, and LKWY. If it doesn't start with a "Y," they aren't archiving it. Shrug.
This page still teaches interpretation of the old-style seismograms for now. The new ones won't be as easy but I'll try to find some examples. In the meantime, carry on and thanks for watching.
"Keep calm and move along." What does it mean?
It's been, uh, 18 hours and 20 minutes now that I've had that message up on one single page of my site, and the freaking out is in full swing... but that message is only there because of freaking out. This server is on a dual-core 1.6 GHz Compaq Presario with less than a gig of RAM, the server is in my bedroom, and my cable modem is what links it to all those hungry browsers out there. And every time one of the seismograms looks Really Really Colorful, several websites out there (I hesitate to call them "notorious" but...) directly embed huge 200K+ seismograms off of my site directly into their articles when they could instead simply download them themselves, or link to them on the USGS site. This has been happening for more than a decade now, the actual provable real swarms don't even generate as many page hits, and it's high time everyone out there got some education in:
This is a very, very, very easy thing for anyone to do, regardless of their knowledge; this lesson is all you'll need. Go here, the page everyone looks at all the time. That page is for January the 7th, 2004, a day on which there actually were nine earthquakes in Yellowstone, the first one worryingly-large. I want you to notice a few things, please...
With those guidelines in mind, examine the page everyone started freaking out about (this time.) Categorize all the signals you see. There are a couple of obvious, large-ish quakes visible on every seismometer. One of them is a magnitude 3.04, not even as large as all those quakes on 1/7/04. But that's not what everyone's freaking out about. They're freaking out about YMR, YNR, and YHR. Don't they look dramatic? All those colors, so much activity... so much, in fact, that if it were seismic activity, every single seismogram that day would look just like them, all the way to Madagascar. That is not seismic. It's noisy data lines, or miscalibrated equipment, or high winds, or lots of trucks driving by, or mating meese, or a Beyonce concert in Denver. It is not earth movement, magma intrusion, or harmonic tremors. We know what those look like; go look up some seismograms taken of Mt. St. Helens erupting. Fascinating stuff... and Yellowstone looks nothing like it. Yet one of the pages linking to those images has the headline "Panic Time Yellowstone Explodes Off The Charts." It's doing nothing of the sort. THIS is "exploding off the charts"... but even then, during one of the largest quake swarms ever seen there, it didn't erupt. It will have to look a lot worse than that before any real geologists really get really worried. Trust me. Really.
So that's why I wanted everyone to stop freaking out, to just calm down and get on with their lives rather than trying to inject some excitement by choosing to believe the opinions of non-geologists on Youtube or SomeBlogSomewhere.com rather than someone like me who actually knows what they're talking about, but the message seems only to have inflamed everyone's fears. So I've changed the message to green, to prevent Pavlovian panic responses programmed into apparently the entire human race, but the message is the same. There's nothing to worry about now. And if you ever see it change back to red, the words will be different too. They'll say, "Okay, now it's happening!" It will be impossible to miss for those who know what signs to look for and what signs can be ignored. Anyone who shows you an image like YNR's up there and claims it's huge massive cataclysmic earth movement either doesn't know what to look for, or is only saying it to get people to pay attention to them. ("Lying," as we scientists call it, or "sensationalism" to the layperson.) If everyone stopped buying into it, my poor web server would be a lot happier.
For further help in interpreting seismograms without being afraid of every squiggle on them, please see this video, which I wish I'd known about earlier.
And while if I still have your attention, let me explain harmonic tremors to you. This is an aspect of seismology that people seem to
know the least about. HTs occur when gas or liquid rock goes glugging its way through hollow tubes, usually in the build-up to
a volcanic eruption. It's a bit like playing a didgeridoo, or noisy ancient plumbing. These movements resonate at some given
frequency, depending on the size and shape of the tube and viscosity of the medium. They almost never occur at a frequency
slower than 1 Hz or more than 30 Hz. Now, the seismograms on this site (or any other) have enough room for 15 minutes of time (900 seconds)
across the X axis, and 720 pixels to do it in. That means each pixel is averaging together a whole 1.25 seconds' worth of data,
and that means the fastest peak-to-peak it's capable of showing is 0.4 Hz... far below harmonic tremors. In short, this means
you will never be able to see harmonic tremors on any seismogram, at least the ones at Yellowstone. Now, some of you may
be familiar with this seismogram
on Wikipedia, which shows harmonic tremors, and say "Aha, look here, Mr. Smarty!" but I'm afraid I must burst your bubble. That
seismogram is actual ink-on-paper. Since that method doesn't use pixels, every sweep of the pen gets drawn, nothing gets averaged
into a data blob. Also, its X axis is much more expanded than those of seismogram GIFs. There's no scale visible, which means it's not easy
to guess, but it looks like the width of that entire image represents about 90 seconds. HTs would absolutely leap off the page at
you at that resolution, just as they do in the image. Web seismograms just aren't capable of it. So don't listen when someone tries
to tell you one of them is showing harmonic tremors. Because it ain't.
One phenomenon frequently mistaken for HTs is known as "teleseisms." That means "distant earthquakes" in Greek or Latin or something. This YFT seismogram shows two teleseisms starting at about 22:29 UTC and 00:41 UTC, caused by two earthquakes in the Solomon Islands, a 6.9 at 21:45 UTC and a 6.8 at 23:59 UTC. Yes, it takes teleseisms a long time to get through all that planet, about 42-44 minutes from the Solomons to Yellowstone. Any sensitive-enough seismometer on the planet will pick up a quake bigger than magnitude 5.3 or so, but they're pretty faint. YFT is set to 125 µV, which is really very sensitive, so they show up there. The YMR seismometer is also set to 125 µV, and sure enough, it shows up there too. You just have to look hard to see it through all the perpetual noise YMR always has. So when you see it, don't think "harmonic tremors, o noes!" Teleseism frequencies are way, way slower than HTs. That's why you can see them. (PS: the long green smear at 18:50 UTC was a magnitude 4.8 quake that hit near Las Vegas. Even from that far away, the leading edge looks nice and sharp, like a local quake. See how tricky reading these things can be?)
Thanking you for your desire to learn,
– Brett
PS: I have no affiliations with anyone when it comes to this site. I wrote it, I host it, I maintain it, I improve it now and then, and nobody else has ever been involved. Anything you see appear on here came out of my mind; I'm not a disinformation relay. I WILL tell everyone who views my site once the signs are at long last getting really bad, but by then, everyone will probably already know. So no more "You're working for Them!" accusations, please. And besides: everyone's "working" for Them. If you disagree, you just haven't felt the chains yet. Carry on.