During July 8-10, 2019, an extremely energetic earthquake swarm broke out at Mt. Hood. Swarms at Mt. Hood, especially in this location, are quite common. However, they usually do not carry this much energy in such a short time frame. Most swarms in the past are part of local tectonics, but the characteristics of this swarm may indicate something more. Please click the title of this post or "read more" to continue...
First off, if you wish to see all reported earthquakes for the entire swarm period at Mt. Hood, please use the USGS EQ map button above. There is also a 2nd button which shows all available stations in the Mt. Hood area.
July 9-10, 2019 Mt. Hood swarm
Start of first burst: July 9, 2019 at 15:47UTC
End of first burst: July 9, 2019 around 22:39UTC (about 6 hours and 52 minutes; though some quakes occurred between bursts)
Start of second burst: July 10, 2019 at 02:56UTC
End of second burst: July 10, 2019 around 05:58UTC (about 3 hours and 2 minutes; though some tiny quakes occurred after this time)
Total earthquake count (includes even the tiniest, unreported events): This is determined by analyzing the P/S wave arrivals from 2 of the closest stations to this swarm. Some were so tiny that they only appeared on TDH. However, you can easily tell if something is an earthquake by experience and judging P/S wave arrivals. Remember, there is a difference between an obvious earthquake and a locatable earthquake. For the first burst of swarming, there were approximately 207 earthquakes in total, counting negative magnitude earthquakes as well. For the second burst of swarming, there were approximately 91 earthquakes of all sizes, including negative magnitude quakes. That means there were a total of approximately 298 earthquakes of all sizes during the two bursts of seismicity. This number may be slightly larger, seeing it was hard to separate some of the events because many were occurring very quickly. Most of the earthquakes that were unreported likely were not able to be located. However, they were earthquakes nonetheless.
Reported count: For the time period stated above, for both bursts, USGS/PNSN reported 83 earthquake events, including a few tiny aftershocks after the second burst. If you count all earthquakes within the 2 days of seismicity, from July 8 through July 10, they reported 111 earthquakes. Please refer to the USGS EQ map button in the beginning of this post to see all reported earthquakes. Again, I am only dealing with the two main bursts of seismicity for July 9-10, 2019 for the plots below.
Largest reported earthquake of this whole swarm (both bursts): A total of 4 M2.1 events between 3.6km and 4km in depth.
Severity: Major (major for the Mt. Hood area; magnitudes were not large, but the energetic nature of this swarm makes this one of the most energetic swarms at Mt. Hood; possible magmatic fluid migration, along with tectonic activity)
As of right now, July 27, 2019 at 03:00UTC, random aftershocks from this swarm still continue under Mt. Hood.
The first main burst in seismicity occurred at 15:47UTC on July 9, 2019 and lasted approximately 6 hours and 52 minutes. There were a total of approximately 207 earthquakes of all sizes in this first burst alone. The slideshow below contains 61 images.
The second burst of seismicity started at 02:56UTC on July 10, 2019 and lasted approximately 3 hours and 2 minutes. There were a total of approximately 91 earthquakes of all sizes for the second burst. The following slideshow contains 23 images.
This blog page is solely for interesting earthquake swarms that occur in locations other than the ones I already have posted. Pretty much any earthquake swarm I am interested in, that cannot be placed on other pages, will be placed here. Please click the title of each post or "read more" to view each swarm.