April 29 and April 30, 2019 swarms

Yellowstone was very quiet throughout the month of April. Almost too quiet. There were only just over 50 quakes reported for the infamous super-volcano for the month of April 2019. Of course not every quake is reported, especially during swarms, but I can confirm it has been eerily quiet. However, from April 29 through April 30, two minor-moderate rapid fire swarms broke out at Yellowstone. The April 29 swarm was of the rapid-fire variety and struck on the eastern shores of Lewis Lake, just southwest of West Thumb Lake. The April 30 swarm struck near Mary Lake and was smaller in magnitude, but still did carry some energy. In this post I will simply show some information and plots dealing with these two swarms. If you haven't already, please click the title of this post or "read more" to continue...

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Resources:
-For seismic audio of the April 29, 2019 swarm, scroll to the end of this post.
-If you wish to see all the seismic stations at Yellowstone, please CLICK HERE.
-USGS earthquake map of reported events for April 29-30 (shows both swarms): CLICK HERE

April 29, 2019 - Lewis Lake

If you wish to see which earthquakes in the plots below were reported, simply goto the link I provided somewhere above that shows you the USGS earthquake map for Yellowstone during this time period. Earthquakes are reported in UTC and the times on the plots are in UTC as well. Also, I do not detail every single event of the swarm in the plots below. However I do try to show most of them. You can also find the locations of all stations at Yellowstone by looking for the two links I posted in the beginning of this post.

As you can see, this swarm did occur on the eastern shores of Lewis Lake, just southwest of West Thumb Lake. This swarm was of the rapid-fire variety, a type of swarm that dominates seismicity in this area. The swarm lasted approximately 34 minutes and the largest magnitude was reportedly M2.6. Here is are spectrogram plots of the entire swarm:

Information detailing this swarm is as follows. Estimated total earthquake counts are taken by comparing P wave arrivals to surrounding stations. You can tell only a fraction of the events were reported, though the unreported events are pretty small.

April 29 swarm:
 
Start of swarm: 5:10UTC
End of swarm: 5:44UTC
Total earthquake count (includes even the tiniest, unreported events): ~55 events
Reported count: 6
Largest reported earthquake of this swarm: M2.6 at 3.0km depth
Largest amplitude: ~211,600 (YDD-HHZ), ~32,800 (YLT-EHZ)
Severity: Moderate
# of 3-plot images below: 12


Helicorders in slideshow format:

Seismogram, spectrogram, spectra plots of many events during this swarm:

For seismic audio of the April 29, 2019 swarm, please watch the video below. I suggest using headphones for the audio but be wary of the volume! Skip to the 23:29 time mark:

April 30, 2019 - Mary Lake

If you wish to see which earthquakes in the plots below were reported, simply goto the link I provided somewhere above that shows you the USGS earthquake map for Yellowstone during this time period. Earthquakes are reported in UTC and the times on the plots are in UTC as well. Also, I do not detail every single event of the swarm in the plots below. However I do try to show most of them. You can also find the locations of all stations at Yellowstone by looking for the two links I posted in the beginning of this post.

Although the image above only shows two reported earthquakes for this location, they upped the count to 6. But as you are about to see, this swarm did indeed contain more than 6 earthquakes. This swarm carried smaller magnitudes and less energy than the April 29, 2019 rapid fire swarm, but still in my opinion can be labeled a rapid fire swarm. Just barely. Note the swarm epicenter struck somewhat between Mary Lake and the Lower Geyser Basin. This swarm lasted approximately 45 minutes with the largest reported events were two M1.4 earthquakes (see info below).

Here are some spectrogram plots detailing the swarm:

April 30, 2019 swarm:

Start of swarm: 19:52UTC
End of swarm: 20:37UTC
Total earthquake count (includes even the tiniest, unreported events): ~30
Reported count: 6
Largest reported earthquake of this swarm: M1.4 at 2.1km depth, M1.4 at 6.9km depth
Largest amplitude: ~12,200 (YML-EHZ), ~2,300 (YPM-EHZ)
Severity: Minor
# of 3-plot images below: 8

Here are some helicorders from around the area:

Seismogram, spectrogram, and spectra plots detailing most of this swarm: