My name is Jamie Farrell. I'm a seismologist at the University of Utah.
We operate the Yellowstone Seismic Network. Over the last three years we've
been doing some work at the Upper Geyser Basin around Old Faithful using these
smaller seismometersâthis is one of them right here. This little thing right here
has everything in here that we need to record seismic data. So, there's what we
call a geophone in there that's monitoring ground movement in all three
directions: northâsouth, eastâwest, and up and down. It has a battery. We just
basically spike these things into the ground and we can put up to we put up to
you know over 500 of these things in the area. They're very sensitive to ground
movement. One summer we put in just a few stations to see to see the difference
between summer activity and winter activity and we put a few stations in. And
this one in particular that was up on Geyser Hillâso this is away from Old
Faithfulâit's very quiet at night which is what we would expect and then during
the day it slowly ratcheted it up to higher and higher noise levels during
the day but I noticed this sawtooth pattern it was going up and down and I
plotted timing the Old Faithful eruptions. You can see this noise level
from people walking around the boardwalk. It would build up and then
once it got close to an Old Faithful eruption, it would die down because all
those people moved away from this station over towards Old Faithful. And
one of the more interesting ones we found is this this pool up on Geyser
Hill called Doublet Pool and it doesn't erupt or anything like that, but in 2015
about every 40 minutes or so the pool will start to bubble and get agitated
and then the the surface would start to thump up and down. And if you're really
quiet, if you're sitting there in the boardwalk, you can literally feel and
hear these thumps. And interesting enough in 2017 we noticed something different
about the pool, so not only was it happening more often it was happening
about every 29 to 30 minutes instead of 40 minutes in 2017, but each episode was
lasting about a minute or so longer. But really, the focus of these experiments
we've been doing is really been Old Faithful. So we've done three different
what we call campaigns around Old Faithful. So each one of these occur in
early November after the park closes. The first year, 2015, we put in about a
hundred to hundred and thirty-three stations. In 2016 we came back and we did
something a little bit different we did a much denser array
around Old Faithful. And then in 2017 we came back and did more of a general
array around Old Faithful and we moved the dense array up to the Geyser Hill
area, and then we did a bigger footprint across the whole Upper Geyser Basin. If
you look at the seismic signals recorded around Old Faithful, you see this kind of
general build up of what we call hydrothermal tremors the seismic signal
for the actual eruption is much smaller than this pre-, this pre-play. And what we
figured out that we're seeing here is that you know as Old Faithful is
building up towards an eruption, the underground plumbing system is filling
up with this super-heated water. And you have these bubbles being formed. They
reach the top of that water column where it's relatively cooler than
where these bubbles were formed and they implode. And when those bubbles implode
that creates this seismic signal that we're recording. If it's the same
every time or if there's some predictable decay on that, then there is
potential for us to really be able to predict Old Faithful eruptions very
accurately, probably within, you know, less than a minute. One interesting
thing that you can do with these really dense seismic networks is you can look
how these seismic signals travel through this area that's covered by these
seismometers and and we can really look and see, you know, what's going on as these
seismic signals travel through the earth. As we saw that there was this
one area, just basically to the west of Old Faithful,
where it was consistently delaying seismic signals as they traveled through.
We interpreted that as as this underground reservoir of hydrothermal
fluids that's feeding Old Faithful. And what we found is when these seismic
signals travel through this this body this, you know, it's not just open body of
water underground, it's really just a series of probably fractures that are
filled with hydrothermal fluids in this area. But that, those fluidsâthe presence
of those fluidsâchanges the way these seismic signals travel through this area.
And what we see is that once these seismic signals travel through here they
kind of get trapped in this area; they just bounce back and forth and
reverberate and keep in mind these are very small signals; you can't feel these
yourself. These are very small only of these instruments these very sensitive
instruments see these, and so this can really tell us
about you know if there was a larger earthquake in the areaâsay like a
Hebgen Lake 1959âthose seismic signals that travel through the same low
velocity body and get trapped and that has implications for seismic hazards in
this area. So, the Old Faithful Inn is sitting right on top of this body.
And in fact, the Old Faithful Inn was damaged by the Hebgen Lake earthquake
that some of the the the large rock chimney collapsed. This is coming fall,
this November, we're gonna do similar types of experiment,s only we're going to
move to Norris Geyser Basin. They're in different geology these two Geyser
Basins. The other thing is Norris is one of the hottest areas in the park and
it's also very dynamicâthere's always new features popping up here there. And
also Norris Geyser Basin is home to one of the tallest
active geysers in the world: Steamboat Geyser, which actually is just erupted.
If we get lucky, maybe steamboat will erupt while various instruments are in the
groun;d that'd be very lucky. But, in Yellowstone is is the location of some
of the largest what we call hydrothermal explosions in the world. And these things
happen every year and most of time they're small and they're in the
backcountry so they're not a hazard to people but they have happened in front
country geyser basins before. And what happens is these hydrothermal systems
these kind of nutrient-rich waters are coming up from underground and they
erupted and they form these really cool pools and stuff like that, but they're
also depositing these minerals as they come up through the plumbing system. And
sometimes they clog themselves up, and that pressure builds up and builds up
until it releases it in what we call a hydrothermal explosion, where you're
releasing hot mud, hot water, hot gas, and then rocks that blow out. That might be very
dangerous to people, if it happens, you know, close to the boardwalk. So if there
are any kind of seismic precursors to one of these hydrothermal explosions,
and if we can record those, and then if we can identify those, we can look for those in
real-time. One thing I really like about working in Yellowstone is it's a
very active and very dynamic system. You know, we record anywhere from 1,500 to
3,000 earthquakes a year. Sometimes there's gaps, sometimes we get these
earthquake swarms that we call where you get a lot of earthquakes in
one area and over a short period of time. You know, just last year
we had will be called the Maple Creek Swarm, where we had, you know, over 2,500
earthquakes located near the town of West Yellowstone, and many of them were
felt by people. Honestly, every single year we learned something new about the
Yellowstone volcanic system, and that's, you know, that's the fun of it.