(guitar music)
Hi everyone, I'm Mike Poland, the scientist-in-charge
at the Yellowstone Volcano Observatory,
and I'm here with the monthly update
for May 1st, of 2020.
I'm coming to you from my home again
on an absolutely gorgeous spring day.
I hope that everyone out there is safe and healthy.
And YVO would like to send out a special thanks
to everyone that's providing essential services
during this really challenging time.
And before we dive into the data,
I'd like to discuss two quick things.
First, a new website is coming to YVO.
It's gonna have a new look and feel,
but the same content, the same monitoring data,
same access to caldera chronicles
and background information.
But hopefully, everything will be a bit more searchical.
Now this will be happening in a couple of weeks.
But the new site is live,
so if you'd like to take a test drive,
you can have a look.
It's at usgs.gov/yvo.
Pretty easy to remember.
I also wanted to address some of the earthquake activity,
that we've been asked quite a lot about
by people out in the public.
Some of the earthquakes that are ongoing in Idaho,
and also in the Salt Lake City area.
Now these are aftershock sequences,
from the strong events that happened
near Salt Lake City on March 18th.
There was that magnitude 5.7,
and also in central Idaho on March 31st.
There was a magnitude 6.5.
The aftershock sequences sort of are the faults readjusting.
After these major events.
Kind of like a house settling in a way.
The stress field changes,
and so the faults have to sort of adjust,
and you get a lot of these earthquakes,
and they tend to tail off over time.
The larger the earthquake,
the longer the aftershock sequence can last.
So in Idaho, we might expect to see aftershocks
that are ongoing for a year.
At least many many months.
Although this will gradually tail out over time.
Still, very unnerving because many of these events are felt.
But these are aftershock sequences.
They're not related to any magmatic activity.
Even though it has the look of a swarm of earthquakes
of the type that we see in Yellowstone.
These are related to the settling of these faults
after the major events that occurred in mid to late March.
Okay, now let's go have a look,
and see what happened in Yellowstone
during the month of April, 2020.
The University of Utah Seismograph Stations,
which is responsible for the operation
and maintenance of the Yellowstone Seismic Network,
located 134 earthquakes during the month of April 2020
in the Yellowstone region.
The largest was a magnitude 1.9 that occurred on April 3rd,
just west of the park boundary near Hebgen Lake, Montana.
There was also a small swarm of 20 earthquakes,
the largest being a magnitude 1.5,
that occurred just south of West Thumb,
on April 12th to the 13th.
These kinds of swarms are pretty common
in the Yellowstone region.
And in fact, Yellowstone seimicity for the month
is at background levels.
If we zoom out a little bit,
we can see those aftershock sequences I was talking about.
So here's the aftershock sequence in central Idaho.
That's following the magnitude 6.5
that occurred on March 31st.
And the smaller aftershock sequence
that's following the magnitude 5.7 earthquake
that occurred on March 18th near Salt Lake City.
More aftershocks in central Idaho than in Salt Lake,
because the earthquake here was bigger.
These are very common
for these sorts of tectonic earthquakes.
They're always followed by these aftershock sequences
that can last months to,
depending on the size of the earthquake,
even years.
Not related to magma movement,
it's really just the fault settling
after the sudden movement that occurred earlier in March.
Turning to deformation,
we're seeing continued trends
of the sort that we've been observing
the last couple of years in some cases.
This is the last two years of vertical deformation
on the east side of the caldera.
The Sour Creek Resurgent Dome
at the White Lake GPS Station.
Each dot is a single day of GPS data.
Downward trends indicate subsidence.
And upward trends indicate uplift.
You can see over this two year period,
the dominant trend is subsidence
occurring right into the present day.
And this subsidence is occurring
at a rate of a few centimeters, an inch or two, per year.
If we move to the west side of the caldera,
and the Mallard Lake Resurgent Dome,
here's a GPS station near Old Faithful.
And we see that same downward trend of subsidence
over the last two years.
Something in the neighborhood of a few centimeters,
about an inch per year.
And finally, looking at the Norris Geyser Basin,
deformation there is a bit more complex.
There had been uplift occurring since about 2015, 2016.
Up until 2018.
In late 2018, that uplift plateaued
and for most of 2019, there wasn't a whole lot of change
at Norris in terms of up or down deformation.
In late 2019, there was an episode of subsidence
that lasted through the end of that year,
about three centimeters, a little over an inch.
And since the beginning of 2020,
there really hasn't been a whole lot of deformation
recorded in the Norris area.
Finally, let's look at everybody's favorite geyser,
Steamboat Geyser in the Norris Geyser Basin.
This is a plot of temperature in the runoff channel
from Steamboat,
and it recorded three eruptions during the month.
First early in the morning on April 2nd.
Second on April 10th.
And the third on April 27th,
and as we've seen with past eruptions,
preceding the eruptions, we don't see much change,
until minor activity of the geyser starts up,
culminates in a major eruption,
and then the minor activity goes away.
The temperature goes way back down again.
And then prior to the April 27th,
there were ten days of minor activity,
which must have been quite spectacular,
culminating in that major eruption,
and then back down to low temperatures.
So Steamboat is continuing its trend of increased activity.
No reason to expect it to stop anytime soon.
Well, that does it for the YVO monthly update.
Remember, if you have any questions,
you can always send us an email
at yvowebteam, that's all one word.
At usgs.gov.
And we're also on social media.
Facebook and Twitter at usgsvolcanoes.
All one word.
Hope everyone out there stays safe and healthy,
and we'll see you next month.
Take care.
(guitar music)