On February 16, 2018, seismic sensors in Montana (Bozeman area) recorded a strange seismic event that happened either locally or in Yellowstone National Park, which is located slightly to the south:
The US Geological Survey remained silent about this moment, as if nothing happened in the caldera that day.
On January 17, the same sensor in Bozeman produced the following picture:
What does this picture mean? We go to the resource archive, open the data of the same sensor for June 14, 2017, when Yellowstone had the strongest earthquake in the past year. We look:
The figure shows a report of a 4.4 magnitude earthquake near West Yellowstone on June 15 (in the United States at that moment it was 14th, as on the sensor). Comparing the data for 06/14/17 and 02/17/18, we come to the conclusion that in February there was no less (if not more) strong earthquake in the caldera than in the summer of last year. That is, the earthquake is about 5.0 on the Richter scale.
Promotional video:
Why are we looking at sensors in Bozeman rather than sensors located directly in the caldera?
There is a well-known service isthisthingon.org, which makes sensor readings available to the public directly in Yellowstone. In theory, this service would be ideal. However, given a certain interest in Yellowstone from the USGS, it would be naive to assume that the sensors there show the truth, only the truth and only the truth.
It is much more reliable to look after the readings of seismometers at some distance from the caldera - they will not underestimate the readings and will not correct them there. isthisthingon.org is also very useful, because it only gives a visual topology of what is happening, that is, it shows specifically under which of the sensors earthquakes occur most often.
However, no one hides the topology: according to the USGS, the site of the first shock was the same area of Maple Creek, where the earthquake occurred in the summer. And if the area of earthquakes is the same, if their strength is also most likely the same, it probably makes sense to recall the summer earthquake in Yellowstone on June 14-15, 2017. What was unusual there?
The summer earthquake in Yellowstone on June 14-15, 2017 will be remembered for the following moments.
Firstly, honest guys from the US Geological Survey first wrote that there was 5.0 points, after which the message was removed from the site and 4.4 was written.
Secondly, after this earthquake in Yellowstone, the so-called Maple Creek swarm began, in which officially recognized tremors were in the thousands and which subsided only by November 2017.
Thirdly, on the eve of the earthquake and immediately after it, NASA's stratospheric observatory, an infrared telescope mounted on a Boeing 747SP, was lifted into the air. Beginning on June 12, he flew over the caldera in circles and photographed something. Something very hot, best seen in infrared light
Unfortunately, what was seen from the observatory was not shown to the public.
Now, having refreshed the events of summer 2017, let's return to what is happening in Yellowstone now. And now there seems to be an intense swarm of earthquakes, with epicenters at a depth of 5-8 kilometers and with rare deeper foci of 10-15 kilometers:
We do not present all the activity of the caldera after February 16. According to official USGS data, the swarm is approaching 200 earthquakes and continues to grow. Although the real thing is much more interesting there and 200 aftershocks were accumulated on February 17th, although the US Geological Survey for some reason is silent about this fact.
Here are the spectrograms generated from data from sensors installed in the area of Mount Baker and Lake Crater, located significantly west of the caldera:
Spectrograms are three-dimensional graphical displays of seismic events, with color as the third dimension. The horizontal scale displays the travel time of the seismic wave, its vertical frequency, and the color - the intensity. Thus, the figure shows that more than fifty small seismic waves arrived from the side of the caldera only on February 17, waves as frequent as if there were some ripples in the water. And it really looks like ripples. Only, unfortunately for the inhabitants of the states of Wyoming and Utah, this ripple is not on the surface of a lake made of water, but on the surface of a magma lake growing under Maple Creek.
Since the people of Montana are not all dumb and people express concern, on February 19, the USGS issued an emergency soothing message signed by local seismological enlightened people - Mike Poland, USGS geophysicist and Jamie Farrell, assistant professor at the University of Utah and senior seismologist at YVO. So the translation:
The current seismic swarm of Yellowstone - what does this mean?
The earthquake has continued in Yellowstone over the past few days. We want to note right away that at the moment there is no volcanic activity in Yellowstone. This is just another small swarm that currently has more than 200 quakes (as of February 18th), recorded in a 13 km (8 mi) square northeast of West Yellowstone, Montana. Moreover, in fact, there are much more earthquakes, but the USGS ignores them for placement due to their extremely small magnitude.
The epicenter of the swarm is roughly the same as the epicenter of the Maple Creek swarm, which occurred last summer and counted 2,400 earthquakes in June-September 2017. In fact, the current swarm may simply be an extension of the Maple Creek swarm, given the sporadic seismicity in the area over the past few months.
Close-up of the seismicity associated with the current swarm (red circles) compared to the 2017 Maple Creek swarm locations (gray circles). YMC is the closest seismic station to epicenter.
The current swarm began on 8 February with a few small events occurring once or twice a day. But already on February 15, noticeable rates and magnitudes of seismicity were observed. As of the night of February 18, the largest earthquake in the swarm has a magnitude of 2.9. They all occur approximately 8 km (5 mi) below the surface.
What is causing this seismicity of the swarm? And why does this part of Yellowstone National Park always see such events? This is not alarming if you look at everything historically. The figure below shows a map of the Yellowstone earthquakes from 1973 to 2017. Red circles are all earthquakes and blue circles are earthquakes that were part of swarms.
Thus, the seismographs of the University of Utah, which are responsible for seismic monitoring in the Yellowstone region, show that this area is simply a seismic source.
Swarms reflect changes in stress along small faults below the surface and are usually caused by two processes: large-scale tectonic forces and changes in pressure below the surface due to the accumulation and / or extraction of fluids (magma, water and / or gas).
The scope of the current swarm depends on both processes. The largest historic earthquake in the region, the 1957 event M7.3 Hebgen Lake, was caused by the mainland warping, the western United States moving away from the eastern, causing the topography of much of the region to change. But we also know that there is a huge amount of liquid beneath the surface, including hydrothermal water and gases, that surface in the nearby Norris Geyser Basin - the hottest thermal region in Yellowstone National Park!
Modern and past earthquakes reflect the geology of the region, which contains numerous faults as well as fluids that constantly move beneath the surface. This combination of existing faults and fluid migration, and the fact that the region is likely still “feeling” the stress effects of the 1959 earthquake, are contributing to the transformation of this area into a focus of seismicity and activity.
While it may sound alarming, the current seismicity is relatively weak and actually represents an opportunity to learn more about Yellowstone. This occurs in times of change when scientists can develop, test, and refine their models of how the Yellowstone Volcanic System works. Past seismic swarms like those of 2004, 2009 and 2010 have led to new insights into the behavior of the caldera system. We hope to expand this knowledge through future seismicity analyzes 2017 and 2018.
Here's a wonderful and entertaining story. It slightly contradicts the official USGS history of “less than 200 earthquakes” on February 21, but the academics explained everything - they do not take into account a trifle. But how small is an earthquake of less than 1.0 magnitude?
Below we give an amusing interpretation of the Richter scale in TNT equivalent:
Thus, the scale allows you to represent what is happening in the caldera not in the form of numbers, but more figuratively. 1-2 points - this is a bomb from the Second World War, caliber 50-500 kg. 3-4 points - this is MOAB or even FOAB - the mother and father of all bombs, respectively. 4-5 points - this is already a nuclear weapon, which, as if from time to time, explodes in the caldera.
If something explodes somewhere 5 kilometers underground with the force of a 50 kg aerial bomb - this, of course, will not be a seismic event that someone will notice, but if a 50 kg bomb explodes at a depth every minute, and all this is happening against the background of explosions of bombs weighing 10-20 tons and after an explosion of about 20 kt (one Hiroshima) …
… probably nothing can be ignored here, which the official seismologists most likely do.
Nevertheless, the figure of 1500 seismic events per week may draw undue attention to the caldera. Therefore, the officials say everything correctly: 50 kilograms of TNT is nothing, no need to worry. And so that people in the state of Montana were even less worried, they were offered a contour map for consideration, where they marked earthquakes for 50 years and directing their thinking in the mainstream: everything is fine, in the same place he is constantly afraid.
However, there is another card on this score. More precisely, a rather rough 3D model illustrating the Maple Creek bed that passes under the surface:
As you can see from this video, the magma chamber beneath the caldera is triple, consisting of successively decreasing levels. There are only three of them:
The drawing, as well as the video demonstration, are based on a 2014 study of the passage of seismic waves below the surface in the caldera region. It is like a huge tectonic apparatus for ultrasound.
A lot of information cannot be obtained from such a study, nevertheless, it is absolutely clear to everyone in Utah since the summer of 2017 that under Maple Creek is the dome of the most superficial magma reservoir.
A deeper reservoir expands under pressure, magma seeks its way to the surface, and when it finds a fault and fills it, an earthquake of magnitude 4-6 occurs first in this place, when the pressing magma sharply pushes the basalt rocks apart. Then the new system stabilizes, generating a swarm of this or that force. It is this process that is reflected on the map of earthquakes in the caldera in the period from 1973 to 2018.
However, in the case of the Maple Creek swarm, we already have something completely different. Namely: two swarms in the same place!
That is, magma makes its way to the surface in the direction of the Maple Creek region, finding the weakest rock on the way. And today magma is already much closer to the surface than in summer, since earthquakes with a magnitude of more than 4.0 points just speak about the advancement of magma, creating a new channel for itself.
The second thing to pay attention to is the depth of shallow earthquakes, which the enlightened ones from the USGS suggest not to pay attention to. If you look at the figure and look at the USGS data on the depth of the current swarm, it becomes obvious WHERE the movement is taking place:
Thus, the main earthquakes in the caldera are now generated in the uppermost magma reservoir, located at a depth of 5-15 kilometers.
The attention of all newspapers is riveted to earthquakes with a force higher than 4.0, therefore, the “trifle” in the form of explosions of 10-ton bombs is neglected by everyone. However, it is these small earthquakes that indicate the inevitable approach of a catastrophe. Perhaps it is already in full swing.
It is impossible to look inside the earth's crust and see what is happening with our eyes, but the only logical explanation for large earthquakes above 4.0 would be the movement of magma to the surface, which occurs in jerks. Somewhere in the rock a crack appeared, somewhere the pressure increased - and the magma rushed there with a loud crash, crushing everything with an explosion force of 20 kilotons or more. But what keeps shaking afterwards? Magma?
Unlike the mass illusion based on video about volcanoes and newspaper terms like “magma lakes”, people imagine that there really is some kind of “reservoir” underground in which magma splashes like hot oil in a barrel. In fact, this is not the case. The magma chamber (surface) looks as follows in the section:
In other words, the reservoir is a mountain of refractory rock crushed into pieces, filled with rock in a melt state. And when the melt becomes more than 50 percent, then the eruption begins.
According to official data for 2014, the melt in the upper magma chamber was no more than 15%. We can neither deny nor confirm this information. Maybe the truth was 15%, and maybe 25% or only 5%.
But it is not by chance that we cited above not just some data from some seismographs in the state of Washington, neighboring to the caldera. We have provided an UNEDITTED spectrogram, that is, a computer-modeled drawing based on the readings of many seismometers. And in this picture, not just “private earthquakes”, but real waves. There are a lot of them at these frequencies.
Similar spectrograms are regularly and honestly shown by the UNAVCO service, which is directly involved in monitoring the caldera:
The conclusion from such a frequency of small earthquakes is very bad, since only a viscous liquid can generate such partial, small, continuous vibrations. Solid rock cannot move like that.
If you pour a mountain of rubble from the back of a truck, in a couple of minutes even the dust will settle there, the stones will stop rolling. But if this rubble is poured into the water, the waves on the lake will walk for an hour. If the lake is not made of water, but more viscous, for example, a lake of oil, the excitement there will be up to a day.
The rock in the magma reservoir behaves in a similar way. If solid rock predominates, the emerging waves in the melt are instantly extinguished. But if there is a lot of melt, the wave will persist for a very long time, causing the same incessant swarm.
And if we see this swarm in Yellowstone, if we see that the magma in the upper reservoir behaves not like a pile of stones, but like a liquid - the critical line in 50% of the liquid rock there seems to have already been passed or is very close. And this means that the eruption can begin at any time.