I’m not sure what to make of it, but while getting my seismofix this morning I came across a quake on the Red Lodge Montana seismograph that didn’t turn up in Google Earth’s very nice USGS plug-in at all. Red Lodge is about 70 miles northeast of Yellowstone. The same event turned up on the seismographs at Bozeman Mt. and Pinedale Mt.
First impression was that it doesn’t look like your standard earthquake so much as it looks like a monochromatic B type event. It looks like resonance. Moreover we do not see a P wave at all here, and as B type events go this is a big fat one. Note the slow onset and smooth waveform diminishing slowly.
I wrote about that earlier in my post here about the Long Period Event, which is the signature of a pressurizing volcano, but let’s not jump to conclusions just yet, this is interesting so far, and that’s all. If we see more of these and increasing in frequency we might have reason for concern.
There is a magma chamber under Yellowstone, that’s no secret, and it’s thought there is a large plume of magma ascending from about 400 miles down in that region as well. It’s believed to look something like this on the right.
What might this mornings event mean in this context? Well, it might be an expansion of the magma chamber in an area east of Yellowstone. It’s really too soon to say. At any rate, as much as I like the USGS plug-in for Google Earth, not everything shows up on it.
I remembered that the Yellowstone hot spot has been moving northeast over the last 15 million years, with caldera forming eruptions every so often, the last being 640,000 years ago in what is now Yellowstone National Park.
The progression of this hot spot from southwest to northeast is shown here, and I think it safe to assume that it has continued moving over the last 640,000 years in the same direction, which would fit in well with this morning’s event, which was recorded most strongly east of the park, at Red Lodge, 70 miles northeast. Makes sense to me anyway. During the last eruption at Yellowstone 15 kilometers of the Galatin mountain range disappeared into the caldera. Gone. Mountain ranges are not immune to super-eruptions.
This morning’s event registered most strongly near the Absorcas northeast of the Yellowstone caldera, right about where we see a saturated and over-pressured fracture zone here on the right. Ah! I find this marvelously interesting! I found this wonderful graphic at the Yellowstone Teton Epicenter page and it does seem to tie right in with what happened this morning. If you were looking for a long period event anywhere around there this is right were you would expect it. I so love finding this stuff out!
Since yesterday’s event noted above a smaller event has appeared on the seismograph at Red Lodge and elsewhere. Tremor is evident, and seems strongest at the Pinedale BW06 station.
This is not the type of event seen yesterday morning, and neither event should be taken to mean that an eruption is coming up at Yellowstone. I’ve been asked what yesterday’s event means and whether it is normal. It was the first time I’d seen that type of event in the Yellowstone area, so I have to say no, it’s not the run of the mill type event. Equally, it may well be a one-off event. Long period events like that happen when magma under pressure runs out of room to expand into and produces resonant vibrations in the surrounding geologic structure. That’s really all we can say at this point.
The YPK station, easternmost in Yellowstone records the following just after midnight: