Nov. 2019 - Two Small Energetic Swarms and a Strange Event

Yellowstone has been fairly quiet in past months. However, there were 2 minor rapid-fire swarms in November 2019 along with a strange event I cannot wrap my head around. Please click the title of this post or "read more" to continue...

Strange Event

After the small rapid-fire swarm on November 25, 2019, there was a strange event that appeared on seismic stations across the NW quadrant of Yellowstone National Park on the 26th. It was extremely strange. However, I have seen this type of event before and still am clueless as to what could cause it.

It is travels too slowly to be seismic in nature but also seems to travel too fast to be related to any surface activity. These events have mid-range frequencies but most power is kept below 10Hz. I like to keep track of these events, since they are odd, so here is a quick outlook on these events.

The first event was smaller than the second and can be seen below, using the closest seismic stations I could find.

Here are the second set of events that occurred soon after:

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Nov. 25 Rapid-Fire Swarm

On November 25, 2019 there was a rapid-fire swarm just a couple kilometers south of Mary Lake. It was minor, but still did occur. The swarm started at 20:10UTC and lasted only 9 minutes. However, approximately 25 micro-quakes struck within those 9 minutes. Only 8 earthquakes were reliably located with the largest being a M1.1 event at 6.1km in depth.

CLICK HERE for the USGS EQ map for reported events of this swarm. Below are helicorder and seismic plots of this swarm.

Below is the seismic audio to this swarm. All audio is retrieved from IRIS and this audio has been sped up to allow us to hear it. The speed is 8,200 samples per second. Headphones are suggested, but be wary of how loud it gets.

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November 30 Rapid-Fire Swarm

On November 30, 2019, a rapid-fire swarm broke out along an east-west zone along the central shores of West Thumb Lake at Yellowstone. Swarms like these are common and have occurred many times in the past. Proof of this can be shown if you CLICK HERE.

The swarm started at about 08:09UTC on the 30th and lasted approximately 36 minutes. The two main bursts of the swarm, since it was very energetic, were 08:09UTC to 08:27UTC and 08:36UTC to 08:38UTC. For whole swarm there were approximately 75 earthquakes with many being too small and too emergent to be located. Regardless, 11 were reliably located with the largest being M2.1 at 3.7km depth. CLICK HERE for the USGS EQ map of reported events for this swarm.

Below are helicorder and seismic plots of this swarm.

Below is the seismic audio to this swarm. All audio is retrieved from IRIS and this audio has been sped up to allow us to hear it. The speed is 8,200 samples per second. Headphones are suggested, but be wary of how loud it gets.