Since December 1, an earthquake swarm is hitting beneath the eastern part of Yellowstone Lake.
This high seismic activity occurs along an ancient fault that formed when the supervolcano last erupted 631,000 years ago.
Could it signal the reactivation of that boundary fault?
Why is this Yellowstone swarm so interesting?
Although the current swarm looks very impressive, it is pale in comparison to one of the most famous seismic series to have happened since the formation of the Yellowstone Volcano Observatory, the 2008–2009 Yellowstone Lake swarm.
The seismic series is interesting as it is slightly larger than the average swarm in terms of numbers of earthquakes.
It is known that the real risk at Yellowstone isn’t a supereruption but a powerful earthquake… And it is known that such ‘Big Ones’ can be initiated by enhanced seismic activity.
What is the 2008–2009 Yellowstone Lake swarm?
The 2008–2009 swarm began on December 27, 2008, in northern Yellowstone Lake and lasted for around 11 days until January 7, 2009, migrating north over time at about 1 km per day.
It was initiated by a M4.1 earthquake which was followed by more than 800 aftershocks.
The migrating series was accompanied by surface deformation indicating fluids moving through the shallow crust.
And this seismic event remains the only time that GPS stations in Yellowstone have recorded deformation related to an active earthquake swarm.
Up to now, it is unknown what type of fluid was moving (water, gas, magma, etc.).
The 2020 Yellowstone Lake earthquake swarm
In comparison, the current swarm is much weaker in terms of total numbers of events (about 150) and the energy they have released.
Moreover, the seismicity in this current swarm doesn’t seem to be migrating with time.
However, the 2020 swarm occurred directly on the boundary of Yellowstone Caldera a fault which formed due to collapse of the surface during the most recent large explosive eruption 631,000 years ago.
Could this swarm be a reactivation of that boundary fault?
Swarms on caldera-bounding faults are relatively common.
For example, earlier this year, on September 10, 2020, another swarm occurred with about 100 located earthquakes in 24 hours (the largest was magnitude 2.8).
This swarm was located where the southern part of the caldera-bounding fault intersects a regional fault zone.
Existing faults and cracks are weak zones that are frequently prone to slipping, especially in the presence of hydrothermal fluids like those that are found in abundance at Yellowstone!
While the Yellowstone is currently being hit by swarms of earthquakes, a new study explains that the Yellowstone hotspot is waning.
When will the 2020 Yellowstone earthquake swarm stop?
At this point, it doesn’t look like the current swarm beneath Yellowstone Lake will approach the size of some of the larger swarms that have occurred in the past few decades.
But one never knows how things are going to go, especially when it comes to earthquakes.
One thing is sure, Yellowstone will continue to have earthquake swarms like this in the future. And keep in mind… While Yellowstone supervolcano eruption rumors are back, Cascadia is the real Big One!
So now it’s time to get the real version of the story about the volcano threats on the U.S. West Coast and watch the most informative and spectacular documentary ever done on this subject here (click on the image below).
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