Yellowstone, Any Harmonic Tremors?

I know many of you are watching the Yellowstone webicorders. What we want to watch for are “Harmonic Tremors”. What are they and what do they look like?

During the first week of April a different type of seismic signature was showing up on seismograms from Mount St. Helens. On April 1 the first weak harmonic tremor was detected. Stronger bursts of harmonic tremor were recorded on the 2nd. The seismogram above is an example of harmonic tremor recorded at seismic station RAN on April 2. (Image courtesy of the Volcano Hazards Program website)

Do you see those up and down lines, third from the top? Those are Harmonic Tremors and signal magma movement.

Click on image to enlarge

This is the webicorder image of June Lake (JUN) which covers the time period in question. The low frequency waveforms are visible about 2/3rds of the way down.
Click on the image for the1282x886 GIF [174,366 bytes]

Have we seen anything yet at Yellowstone? Here’s a link to the webicorder at the lake.

So far nothing yet.

31 Responses to “Yellowstone, Any Harmonic Tremors?”

  1. Let me first admit that I know absolutely nothing about volcanoes or geology in general. I am, however, fascinated by the subjects.

    I’ve been reading that the harmonic tremors are being detected and have been since last night. This may be just Internet noise. What do you think?

  2. Roger, if I understand what harmonic tremors look like on a webicorder, there haven’t been any and I haven’t seen any U of Utah officials say they’ve detected Harmonic tremors.


    Harmonic tremors just not in the lake.

    heres a link to all of the seismos

  4. Kevn, I don’t see any Harmonic tremors as defined by my post. Doyou have any authority that defines your example as harmonic tremors.

    Roger where have you read there are harmonic tremors?

  5. Sorry, one more. See anything here?

  6. This is off the topic of Yellowstone, but I noticed yesterday (Dec. 30th) there was a small (1.8) earthquake at Wishram, WA which is on the Columbia River at Celilo.
    I had never thought about it before, but I wonder what type of cataclysmic event took place to create Celilo Falls, which is 40 miles north of Maupin.

  7. harmonic tremors
    HT in the comments
    summation from a lay blog

  8. Hey there,

    I think we have harmonic tremors in yellowstone now.
    I think something is about to happen there.

  9. WHats the noise on the graph then? A continuous quake?

  10. Looks like I stand corrected:

    From The Digital Journal of Science at

    “What worries scientists about the the recent swarm of quakes is that a large number of harmonic tremors have occurred over a small area. Such quakes indicates magma movement beneath the surface which points to intense volcanic activity.”

  11. Hey Mike, Just a note of thanks for your coverage of geological events and best wishes in the New Year. Thanks a bunch, Mike (in Central OR)

  12. Hi Mike,

    I’m sorry I didn’t get back to you on this. The site that had the HT information was the same one that bap2 linked to.
    If we’re all correct here, there could be a significant event about to occur.

  13. Either these are just being affected by wind, or continuous HT

  14. Chris, they appear to be continuous HTs

  15. Has anyone read or heard anything from the U of Utah people concerning the HTs?

  16. This always make for an interesting comment to read

    from the Denver post (

    The Wyoming Office of Homeland Security is reviewing Earthquake Response Plans and also monitoring the seismic activity that has been felt by Park Service employees and guests at the park.

    have not seen much else in way of news about them. I suppose the next BIG news cycle will be when the first 4+ quake is detected.

  17. Interesting data analysis from an IT guy:

  18. Here is a little image I compiled.

    Your example of harmonic tremor on the left and then a live seismograph reading from Yellowstone on the right (taken 1-2-09).

    You be the judge.

  19. This is all interesting comments. I’m surprised that one thing is missing from all of this – ground movement. If you search for it on Google, you’ll see that at most monitoring stations of the caldera show that the ground is flat from 1997-2005, then heads north rather sharply from 2005-present. What does it all mean? Who knows. The earth is unpredictable and mankind has been missing signs and making false assumptions for eons.

  20. Did you see the USGS site showing that the output from Yellowstone Lake has increased starting about at the same time these newest tremors began (last 6 days or so). Is magma pushing up the bottom of the lake so as to displace this extra water and force it down river?

  21. Christopher, you are right and here are some charts that show the output is rising:

  22. Looks like Old Faithful had some harmonic tremors at around 13:30 to 14:00 MST today (1/3/2009). See the graph at

  23. Harmonic tremors are showing up on the webicorder..

  24. Seems clear there are harmonics now.

    Does anybody know where to get higher quality output than the webicorder pages?

  25. Why is there not more widespread coverage? I’ve been following with some interest for about 5 days now, and what I read is disturbing. I did some more research and it seems that we should be concerned. We are in WI and although far enough away [supposedly] to avoid immediate harm, we are certainly within range of potentially devastating longterm effects, no?

  26. I noticed today’s “Harmonic Tremor” too, it was picked up on all seismographs at Yellowstone. It was a Very Long Period harmonic tremor (VLP). Seems to be focused on the north end of Yellowstone Lake, like previous tremors. I can’t wait to see what Yellowstone Volcano Observatory has to say about it.

    Someone posted a graph of river discharge out of Yellowstone lake verses Harmonic Tremors, there’s a correlation. It suggests that increased hydrothermal fluid flow is responsible for both; the north end of the lake has many huge hydrothermal explosion craters (e.g. Indian Pond) and the lake bottom is riddled with hot springs. If anything happens, its more likely it will be a hydrothermal explosion rather than a volcanic eruption.

  27. Ok, I just figured out what the “Harmonic Tremor” picked up on the Yellowstone seismometers on the 3-4th Jan really was. It was caused by two very distant 7.4 and 7.6 mag earthquakes in Indonesia, that happened at 19:43 UT and 22:34 UT, it took 1/2 hour for the seismic waves to arrive at Yellowstone. They show up on all broadband and long period seismometers across the US e.g. at Cooper Cave Tennessee.

    Any other similar low frequency “Harmonic Tremors” are also very large distant earthquakes, they are not due to Yellowstone magma. I’m a bit embarrassed about what I said earlier.

  28. Dave, interesting theory. But if that’s the case, why isn’t there such pattern in the YMV station in the park?

  29. I’ve been following the Yellowstone Volcano for a few months now, and what I find to be somewhat curious is that Yellowstone has pretty much quieted down from its activity of 7 months ago. If anyone reads this post and has some additional information for me, I’d appreciate a direct e-mail at My concern here is that the government is filtering out the data being posted to the webicorders Now I know everyone is going to say how that it would take quite a bit of govt intervention to take the data off the web in that short of time, but remember that most websites showing webicorder data, earthquake data, volcano data take anywhere from 15 minutes to an hour to show up on the web. More than enough time to filter out any particular data that would alarm the public. I have noticed that all of the data that has been posted to the web regarding these harmonic tremors is no longer available on the govt websites. I do not know if these are truly harmonic tremors or not, I’m not a geologist by any means. I would hope that there would be enough people out there who live in the wyoming area who would say, ” what was that” and ask questions when the government does not admit that the ground was shaking. I’m not a big govt conspiracy theorist, I do believe that the govt keeps alot of things from us, and probably for good reason, but I for one, would like to know if my neighbor state to the west (Wyoming) is going to be a gigantic hole in the ground when I wake up in the morning. I live in S.Dakota, and while I’m not worried about getting carried away in the blast, the thought of having to shovel ash in the middle of july does not appeal to me either. Send me an e-mail if you have any information about the current situation of Yellowstone that you have that is contradictory to the information currently being published by the govt.

  30. Take a look at the seismographs at Yellowstone from today.

    Sure looks like harmonic tremor to me. It can be seen all over the park…

  31. MikeCinTheOC, I looked at the USGS and only saw small quakes under 2.0. I’m wondering if the earth isn’t ringing from the 7.8 near New Zealand and it’s being picked up in Yellowstone. This has happened before.

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