September has been a very active month for Long Valley Caldera. Starting on September 13, a fairly intense period of seismicity started primarily around the eastern section of Mammoth Lakes, which resides in the SSW section of Long Valley Caldera. The magnitudes were not large, not surpassing M3.0, but the quantity of events were substantial in the short period of time they occurred. Please click the title of this post or "read more" to see some information about recent swarming at Long Valley Caldera.

Starting on September 13, 2019, a fairly intense swarm of seismicity broke out just barely east of Mammoth Lakes. Mammoth Lakes resides within the infamous supervolcano along the SSW section of the caldera. The image above shows all reported earthquakes of all magnitudes from September 13 through September 30.

Swarming was intense but magnitudes were small, the largest being a M3.0 on September 25. Most of the seismicity was concentrated within specific "bursts" of rapid-fire swarming on September 13, 14, 15, 25, and 29. The biggest swarms were on September 13 and September 25 with the swarm on the 13th by far being the largest of the month.

From September 11 through September 30, there were a total of 856 earthquakes reported for this one location within Long Valley Caldera. 52 earthquakes reported were M2.0+ with only one M3.0. For the entire month of September, for the whole caldera, there were a total of 1,073 earthquakes reported.

Below is a time/depth plot of the reported earthquakes from these many swarms. The image just prior to the plot is the location of the plot "box".

Something quite interesting is that the September seismicity was non-linear in formation, meaning it appears local tectonics did not play a huge role in creating the swarms. Tectonics may still play a small part, but fluid migration from the magma system seems to be a more likely culprit.

The depth of all of the swarms combined is also interesting. Around 3/8 of the earthquake swarms were at 5km depth or deeper. The ceiling of the Long Valley magma system is also around 5km in depth. So it seems the swarming was occurring along the ceiling of the magma system and above it as well.

This can clearly be seen via the image below. Dots are earthquakes for seismicity from Sept. 11 through Sept. 30. This is a cross section of the earth in this location. Imagine you are underground and looking to the north while these earthquakes took place. You can tell it was occurring around the ceiling of the magma system. CLICK HERE to play around with this cross section plot yourself!

Next I will show some quick data pertaining to the swarms that made up the September increase in seismicity for Long Valley. For the two largest swarms, the Sept. 13 and Sept. 25 swarms, I will show a spectrogram "stream" from three of the closest stations since there were too many events and too little time to create custom plots for those two swarms.

This is the swarm that kicked off the entire swarming in this location for September. It was extremely energetic but only reached M2.9. Many earthquakes were also too small and too closely spaced to be located accurately. It is likely many hundreds of events occurred this day.

Sept. 13, 2019 swarm
 
Start of swarm: Sept. 13, 2019 at 02:35UTC
End of swarm: Sept. 13, 2019 at 12:25UTC (about 9 hours and 50 minutes for the main swarm on Sept. 13)
Total earthquake count: Likely 2x or 3x the amount reported. Earthquakes mentioned in this text are for specifically the time period stated above. Many more very small micro-quakes randomly occurred after this time period.
Reported count: For the time period stated above, USGS reported 294 earthquake events of all sizes. Please refer to the USGS EQ map button in the beginning of this post to see all reported earthquakes for all swarms mentioned on this page.
Largest reported earthquake of this swarm: M2.9 at 5.9km depth
Severity: Major one-day swarm
Closest seismic station to swarm: MEM in the NC network

Below is a video of a spectrogram "stream" from three of the closest stations. You can see there were far more than 294 events.

There was swarming basically all day on September 14. The main concentration of swarming started at about 12:52UTC and ended around 13:31UTC. The main concentration of swarming contained around 80 earthquakes of all sizes, many being very small.

The reported count for all of September 14 was a total of 81 earthquakes. Here are helicorder plots from the 3 closest stations to the swarm. Afterward, I will show seismic plots of some random events from this day.

Swarming was sporadic on September 15. There was a quick burst of around 10 tiny events for about 3 minutes at 03:11UTC. Small quakes occurred here and there until around 11:06UTC where around 15 micro-quakes struck until 11:13UTC.

The main seismicity this day started at 14:40UTC and ended around 14:51UTC. This main burst contained approximately 30 earthquakes with some striking in a very rhythmic pattern.

Below are the helicorder plots from this day and also the seismic plots to many of the events on September 15. The reported earthquake count for the entire day of September 15 was a total of 47 events.

The Sept. 25 swarm was the largest of September except for the Sept. 13 swarm. Below is some information, helicorder plots, and a video of a spectrogram stream from three of the closest stations. There were so many events I barely had time to count them all or make plots for them.

Sept. 25, 2019 swarm
 
Start of swarm: Sept. 25, 2019 at 04:33UTC
End of swarm: Sept. 25, 2019 at around 18:00UTC (about 13 hours and 27 minutes)
Total earthquake count: Likely 2x the amount reported. Earthquakes mentioned in this text are for specifically the time period stated above. Many more very small micro-quakes randomly occurred after this time period.
Reported count: For the time period stated above, USGS reported 179 earthquake events. Please refer to the USGS EQ map button in the beginning of this post to see all reported earthquakes for all swarms mentioned on this page.
Largest reported earthquake of this swarm: M3.0 at 5.3km depth
Severity: Major one-day swarm
Closest seismic station to swarm: MEM in the NC network

Sept. 29, 2019 swarm
 
Start of swarm: Sept. 29, 2019 at 08:47UTC
End of swarm: Sept. 29, 2019 at 09:51UTC (about 1 hour and 4 minutes)
Total earthquake count: ~115 micro-quakes of all sizes
Reported count: For the time period stated above, USGS reported 26 earthquake events. Please refer to the USGS EQ map button in the beginning of this post to see all reported earthquakes for all swarms mentioned on this page.
Largest reported earthquake of this swarm: M2.2 at 4.5km depth
Severity: Minor
Closest seismic station to swarm: MEM in the NC network

Start on Sept. 1, 2019, seismicity started to increase under the ESE base of Mt. Shasta. Only a few small quakes struck not surpassing M2.1. However, on Sept. 2, three large bursts of seismicity were detected in the same location at Mt. Shasta. The entire swarm, including the 3 bursts, was not large compared to other locations around the United States. But it was a major swarm for Mount Shasta especially when Shasta rarely sees much seismicity.

Please click the title of this post or "read more" to continue.

Starting primarily around 17:34UTC on September 2, 2019, a major swarm broke out at Mt. Shasta in Northern California. It wasn't major compared to other swarms in other locations around the world, but it sure was major for Mt. Shasta. Shasta is usually extremely quiet so swarms like these are somewhat rare.

The swarm saw mainly 3 bursts of seismicity with the 2nd burst striking like a "rapid-fire" swarm that we see at Yellowstone or Long Valley from time to time. This swarm is also one of the largest for Mt. Shasta since at least 1993, around 26 years ago. According to geologists, the last major swarm for Mount Shasta was in 1993 with likely over 50 events recorded in 1 month (LINK).

On Dec. 19-20, 2008 there was a similar swarm but it was much weaker and didn't last as long as the most recent swarm. I will detail the Dec. 19-20, 2008 swarm in just a minute.

Also, for your information, Shasta is an andesitic to dacitic stratovolcano and is the largest stratovolcano in the continental USA in terms of volume. It supposedly erupts every 600-800 years on average based on the past 10,000 years of volcanic activity. The last eruption was supposedly 200-300 years ago, around 1786 or so, and that means we won't see an eruption for a while, right? Well, as of August 6, 2019, the 1786 eruption has been erased from the record. That means we could be in the warning time frame of the next Shasta eruption. I am not saying this swarm will lead to that, but we should monitor Shasta closely over the next few decades.

CLICK HERE to visit the link about how Shasta's 1786 eruption actually didn't happen.

Below I will show some information and data pertaining to this earthquake swarm. Usually I include seismic audio for earthquake swarms, however NCEDC does not have an audio converter like the IRIS Time Series builder does.

Sept. 2-3, 2019 Mt. Shasta swarm:
 
Start of first burst: Sept. 2, 2019 at 17:34UTC
End of first burst: Sept. 2, 2019 at 18:16UTC (about 42 minutes)
Total earthquake count for first burst: ~24 events

Start of second burst (largest burst): Sept. 3, 2019 at 00:14UTC
End of second burst (largest burst):  Sept. 3, 2019 around 00:32UTC (about 18 minutes; though some tiny quakes occurred after this time)
Total earthquake count for second burst (largest burst in terms of time vs quantity): ~39 events

Start of third burst: Sept. 3, 2019 at about 03:59UTC
End of third burst: Sept. 3, 2019 at about 06:56UTC (2 hours and 57 minutes)
Total earthquake count for third burst: ~47 events

Start of entire swarm: Sept. 2, 2019 at 17:34UTC
End of entire swarm: Sept. 3, 2019 at about 06:56UTC
Total earthquake count for entire swarm: ~125 earthquakes of all sizes if you count the some events in between the 3 bursts.

Reported count: For the time period stated above, for all 3 bursts, USGS reported 28 earthquake events. If you count all earthquakes within the total 3 days of seismicity, from Sept. 1 through Sept. 3, they reported 32 earthquakes. Please refer to the USGS EQ map button in the beginning of this post to see all reported earthquakes.
Largest reported earthquake of this whole swarm (all 3 bursts): M2.7 at 7.1km in depth at 17:34UTC on Sept. 2, 2019.
Severity: Major (This is a major swarm for Mt. Shasta, seeing historical seismicity is usually very low.)
Closest seismic station to swarm: LBR in the NC network
Depth of swarm: Between 7.1km and -0.8km in depth.

Below is a quick video showing the depth and spacings of each event via the Interactive 3D Earthquake Viewer which you can find HERE:

Below are the helicorder plots from 4 stations around Mount Shasta. Remember, LBR is the closest station.

Below are seismic plots of the Sept. 2-3, 2019 Mt. Shasta earthquake swarm (39 images within the slideshow below):

Also, about 8 1/2 hours prior to the earthquake swarm, a very strange emergent tremor-like event was spotted on seismic stations around Mt. Shasta. It was not of local, regional, or teleseismic origin and appears solely around Mt. Shasta. Was this event possibly a precursor to the earthquake swarm? Or was this an avalanche? Below is the event from 3 select stations around Shasta.

Again it seems like the Sept. 2-3, 2019 swarm was the largest since 1993 for this volcano. However, I tried to find other swarms since that have come close. The only one I was able to find was the Dec. 19-20, 2008 earthquake swarm. You can see both swarms labeled via the image above.

If you wish to see the USGS EQ map for the 2008 swarm, please CLICK HERE.

Below is some information about the 2008 swarm. As you can see, this swarm was much smaller than the Sept. 2019 one.

Dec. 19-20, 2008 Mt. Shasta swarm:
 
Start of first burst: Dec. 19, 2008 at 17:03UTC
End of first burst: Dec. 19, 2008 at 17:05UTC (about 2 minutes)
Total earthquake count for first burst: No more than 6 events.

Start of second burst (largest burst): Dec. 19, 2008 at about 17:46UTC
End of second burst (largest burst):  Dec. 19, 2008 around 18:16UTC (about 30 minutes)
Total earthquake count for second burst (largest burst in terms of time vs quantity): ~23 events

Start of third burst: Dec. 20, 2008 at about 03:52UTC
End of third burst: Dec. 20, 2008 at about 04:52UTC (1 hour)
Total earthquake count for third burst: No more than 10 events.

Start of entire swarm: Dec. 19, 2008 at 17:03UTC
End of entire swarm: Dec. 20, 2008 at about 04:52UTC
Total earthquake count for entire swarm: ~39 earthquakes of all sizes.

Reported count: For the time period stated above, for the entire swarm, USGS reported 12 earthquake events. Please refer to the USGS EQ map button in the beginning of this post to see all reported earthquakes.
Largest reported earthquake of this whole swarm (all 3 bursts): 3 M2.1 events between 7.4km and 4.7km in depth.
Severity: Minor
Closest seismic station to swarm: LGB in the NC network
Depth of swarm: Between 8.3km and -1.7km in depth.

Below are helicorder plots from 4 of the closest stations to the 2008 swarm:

Below are seismic plots of the 2008 swarm from the closest seismic station:

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.

Long Valley Caldera, a super-volcano which resides in Eastern California, saw a extremely intriguing rapid-fire swarm on June 15-16, 2019. These types of swarms are my favorite and are more prevalent at Yellowstone Caldera in Wyoming than Long Valley Caldera in Cali. This earthquake swarm was spaced into two episodes: one occurring early in the morning local-time on June 15 and the other burst occurred late at night on June 15 as well. I usually label dates/times by UTC, not PST, which is ahead of PST by about 7 hours. This post will contain seismic plots pertaining to this cool earthquake swarm. Please click the title of this post or "read more" to continue...

So, this earthquake swarm was pretty interesting! The two buttons above will show you the reported events for this swarm, including both bursts, and the locations of all seismic stations within LVC (Long Valley Caldera). The map image shown above details the caldera boundary and the location of the earthquake swarm. Although this is likely considered one swarm, I will detail this swarm by both bursts of seismicity. Both bursts occurred in the same location, same approximate depth, and carried the same characteristics. However, both bursts were separated by approximately 13 hours or so.

Below are helicorder plots from 4 of the closest seismic stations to this earthquake swarm. You can see both bursts in seismicity quite clearly.

First burst:

Start of swarm: 12:45UTC
End of swarm: 14:14UTC (Total of 1 hour and 29 minutes, though many of the earthquakes occurred very close together.)
Info: Station used for the plots below for the first burst was MCB, seeing it is much better at recording these events.
Total earthquake count (includes even the tiniest, unreported events): ~93 events of all sizes.
Reported count: 21
Largest reported earthquake of this swarm: M2.8 at 6.0km depth
Largest amplitude: ~320,800 (MCB-HHZ), ~2,100 (MCS-EHZ)
Severity: Moderate

Second burst (June 16, 2019):

Start of swarm: 03:09UTC
End of swarm: 04:02UTC (Total of 53 minutes.)
Info: I had to use MCS for this second burst of swarming, sadly. This is because MCB, the best station to use for this swarm, was seeing some serious background interference during some of this swarm. MCS is a very old station, so the waveforms are going to look a little weird. However, the frequency content on the spectrogram and spectra plots are accurate.
Total earthquake count (includes even the tiniest, unreported events): ~53 events of all sizes.
Reported count: 15
Largest reported earthquake of this swarm: M2.5 at 5.7km depth
Largest amplitude: ~296,000 (MCB-HHZ), ~2,100 (MCS-EHZ)
Severity: Moderate
 
If you wish to see which earthquakes in the plots below and above were reported, simply go to one of the buttons I provided somewhere above that shows you the USGS earthquake map for Long Valley during this time period. Earthquakes are reported in UTC and the times on the plots are in UTC as well. You can also find the locations of all stations at Long Valley by looking for one of the two buttons I posted in the beginning of this post. Also, I do not detail every single event of the swarm in the plots below. However, I do try to show most of them. Severity is a personal determination, with the April 11, 2018 rapid-fire swarm at Yellowstone acting as a sort of baseline for any major rapid-fire swarm. Severity ranges from minor, to moderate, to major. In rare cases, “extreme” will be used. However, I have not seen a rapid-fire swarm that could ever be labeled as such. But you never know what will happen in the future!

Sadly, no seismic audio is available for swarms at Long Valley. This is because the NCEDC, contrary to the IRIS DMC, does not allow for audio downloads.

In this post I am going to discuss and show the details of an extremely peculiar rapid-fire earthquake swarm that just recently struck north of Green River in southwest Wyoming. This earthquake swarm was a rapid fire swarm, kind of like the ones seen from time to time near West Thumb Lake and Yellowstone Lake at Yellowstone, and is one of the craziest and coolest swarms I have ever had the chance to analyze. However a big difference is that this swarm, with magnitudes reaching around 3.0-3.2, contained many low frequency earthquakes. Sometimes the low frequency events were happening in such close proximity that they blended to create a type of low frequency tremor, which is what volcanic tremor is theorized to be made of. It is highly peculiar this type of earthquake swarm, with these magnitudes and this amount of energy, would even dare to strike in SW Wyoming. This was for sure a strange one and this post will detail as much as possible. Please click the title of this post or "read more" to continue, if you have not done so already.

If you would rather watch this as a video, please watch the video below. If you wish to skip to a part you want, please CLICK HERE to visit the video on my YouTube channel.

Around noon Mountain Time on February 22, 2019, an extremely energetic and peculiar earthquake swarm struck just to the northwest of Green River in the southwestern section of Wyoming. This location is an extremely strange location for an earthquake swarm, especially a rapid fire swarm such as this one. This earthquake swarm is for sure one of the craziest and coolest earthquake swarms I have ever analyzed (at least so far), well except for the 2008-2009 dike intrusion of Yellowstone Lake. In the image directly above you can see the location of the earthquake swarm in regards to 4 of the closest seismic stations.

As you will see within the plots below, this earthquake swarm contained mainly low frequency earthquakes with some of them occurring so fast that it sometimes blended to create a tremor-like event. This was a rapid fire swarm, much like the ones seen around West Thumb Lake and Yellowstone Lake from time to time (CLICK HERE). This also contained many low frequency events that appeared to have very similar characteristics to the possible magma resonance spotted during the 2008-2009 dike intrusion of Yellowstone Lake (CLICK HERE; scroll down to possible magma resonance). Also, please note that the depths of the earthquakes are likely to be extremely wrong. Now why is that?

I highly doubt the depths are correct. One of the events reportedly struck at -3.3km in depth, which would be approximately 10,826 feet above sea level. However if you check on Google Earth, the elevation where the epicenters are is about 6,400 feet above sea level. That means, if correct, these events transpired 4,400 feet above the surface of the earth? That is not possible. Plus, as you are about to see in a second, these events even traveled hundreds of miles showing up on seismic stations in Yellowstone Caldera and other areas as well so we know for a fact these events did strike underground somewhere. Sadly, I don’t think the depths will ever be accurately constrained since these were the wackiest low frequency events ever!

Also, there were many, many more of these strange low frequency earthquakes after the time period allotted in the description and plots below. It is entirely possible this strange swarm is still continuing, but in a diminished form. However since this happened this fast, it is likely this will happen again. I am currently contacting professionals to see what their take on this event was. I personally believe this was NOT tectonic, hydrothermal, or mine activity. That is due to the characteristics of the waveforms and the strength of the events compared to how fast they occurred. Now you will notice many of the events occurred in extremely rapid succession. In the plots below, it is almost impossible to view only one event due to how many are occurring. The energy of this swarm was impressive for the types of earthquakes that made up the swarm.

Overall, this was a good sized low frequency earthquake swarm with possibly some VLF events thrown in the mix. This swarm occurred on February 22, 2019 and info about this swarm is shown below:

-February 22, 2019 SW Wyoming swarm:

Start of swarm: 19:51UTC
End of swarm: 20:58UTC
Note: Although I have the time period of the swarm stated directly above, there were many more events after the main burst in seismicity. This swarm was extremely peculiar. In regards to its energy and how often the events transpire, it is similar to the rapid fire swarms seen around West Thumb Lake and Yellowstone Lake from time to time. Even though this earthquake swarm did contain some events with higher frequencies, most are still considered low frequency earthquakes. Also, some of the events that seem to be tremor may be multiple events occurring in such rapid succession you cannot tell them apart. The total estimated earthquake count below only counts the events within the time period stated above.

Total earthquake count (includes even the tiniest events): ~85 (if many of these were earthquakes, it is likely this number is somewhat higher for the time period above)
Reported count: 6 so far
Largest amplitude from closest station: 169,170 (GAWY-HHZ)

USGS EQ map of this swarm: CLICK HERE

Below I will first show 5 helicorder charts. 4 of them will be from the 4 closest seismic stations and the last one will be from MCID at Yellowstone which picked up these events quite well. The chance that any of these were occurring at or above the surface is basically 0 now. After that I will show some random images and then I will show the USGS event pages to 2 select events, along with their custom plots I made. Then I will detail much of the swarm from the time period stated above. I will not be able to show every single event, but I will show alot of them! Remember to always read chart labels first and any captions beneath any images.

Below I will detail alot of the low frequency earthquake swarm via the 3-plot images I like to generate. I will show them in slideshow format. The first slideshow contains 13 of these images, so does the 2nd slideshow. So, what do you think this swarm was caused by? Let me know!

An additional note, it seems there was an interesting increase in SO2 emissions basically in the same area as the swarm, just as the swarm was peaking/calming. Check it out (CLICK HERE to visit video on YouTube):

During October 22-23, 2018, a large earthquake swarm struck off the northern tip of Vancouver Island. Actually, this swarm occurred extremely close to the epicenter of the smaller swarm that struck on February 13-14, 2019. This swarm I will talk about in this post contained many M4's, some M5's, and 3 earthquakes above M6.0. The 3 earthquakes above M6.0 were reported as M6.5, M6.8, and another M6.5 just after the 6.8. Sadly, the depths were not constrained on any of these earthquakes so all of the earthquakes have a depth set to 10.0km in depth. Obviously it is impossible all of the 14 events occurred exactly at that depth, so it is sad that we cannot add that part of the analysis into the equation. Also, this is likely the largest earthquake swarm this area has seen. Although, as seen below, many M6.0 and above earthquakes have struck since the early-1900s, this has the highest concentration and magnitude of any other swarm in this location since the early-1900s. I could be wrong, but that is what it is looking like! In this post I detail much of the swarm via seismic images and plots. If you haven't already, please click the title of this post or "read more" to continue.

Description of these events according to USGS:

-Over the course of 43 minutes on October 22, 2018 a series of M6.6, M6.8 and M6.5 earthquakes occurred off of Vancouver Island, Canada. These earthquakes occurred as a result of strike-slip faulting at shallow depths on the boundary or within the interior of the Explorer microplate. Focal mechanism solutions for the earthquakes indicate rupture occurred on either a near-vertical right-lateral northwest-southeast striking fault, or along a near-vertical left-lateral northeast-southwest striking fault. The tectonics of the Pacific margin of North America between Vancouver Island and south-central Alaska are dominated by the northwest motion of the Pacific plate with respect to the North America plate at a velocity of approximately 50 mm/yr. Convergence between the northern extent of the Juan de Fuca plate (also known as the Explorer microplate) and North America plate dominate the regional tectonics. The Explorer Ridge along the western side of the Explorer plate and the Sovanco Fracture Zone to the south define the boundary between the Pacific and Explorer plates. To the east, the Explorer plate subducts beneath the North American Plate. Eastward of the Sovanco Fracture Zone the Nootka fault separates the Explorer plate from the Juan de Fuca plate. As a result of these forces the Explorer plate is internally deformed and faulted and can produce diffuse seismicity away from its boundaries. Although a larger earthquake cannot be ruled out, previous sequences of large, closely spaced events in this region have not resulted in larger events, including a M 6.6 and M 6.4 in 2008 that were separated by an hour.
The Explorer microplate is heavily deformed by internal dextral faulting, experiencing frequent moderate-sized earthquakes. Within approximately 70 km of these earthquakes, 11 earthquakes of M 6 or greater have occurred since 1951. The largest previous recorded earthquake in this region was a M 6.8 event that occurred on December 17, 1980.

The helicorder charts shown above are from HOLB in the CN network, which is one of the closest stations to this swarm and is the station I used to generate the seismic plot images shown below.

From 00:00UTC October 22, 2018 to 00:00UTC October 24, 2018, over 75 seismic events of all sizes were detected by seismic stations all across Vancouver Island, Canada, and the United States. Some of the largest events, M6.0 and above, were detected on seismic stations all across the world (as earthquakes of that size should). Only 14 of the 75 earthquakes were reported for that time period. The total count was determined by using P wave cross correlation and the true count of earthquakes is likely to be much higher than that. Sadly, the depth was not constrained so that means all of the events show 10.0km in depth which is likely to be very inaccurate. If you wish to visit the USGS EQ map which details the 14 reported earthquake events, please CLICK HERE.

Although the professionals do state events like these have transpired here before, I doubt none have occurred in such rapid succession with such intensity. Until I see otherwise, I do believe this is the largest swarm this area has seen (at least since the early-1900s). A lot of increased activity has occurred over the past few years at both the northern and southern ends of the Cascadia Subduction Zone. What does this mean? I don't know yet, but it sure is interesting! Another interesting thing to note is the fact that many of the earthquakes in this swarm, including the largest ones, contained much low frequencies than what I would expect. Although the closest stations were some distance away, we should have seen higher frequencies than what was shown. I don't know what this means yet, but I am looking into it.

Below I will show the event pages, followed by their seismic plots, of the more important reported events. The events will NOT be in order of time and date. However the slide shows at the bottom should be mostly in order! In the two slideshows I will detail many of the events that transpired during the swarm, especially the unreported events. Remember to always pay attention to all chart labels and any captions beneath any images. Let me know what you think!

In the two slide shows below I will show multiple reported and unreported events. There are 30 3-plot images with 15 of them in the first one and 15 of them in the second one. Use the arrows to skip through the plots. Again, remember to pay attention to all chart labels! As usual, all times are in UTC and all the plots are labeled and dated.

During late February 13th into the 14th, a strange earthquake swarm appeared under the northern section of the Cascadia Subduction Zone, off the coast of the northern tip of Vancouver Island. It is interesting to note, as seen in the image above, that some swarming has been occurring off and on both near the northern and southern ends of the Cascadia Subduction Zone. The largest earthquake of the Feb. 13-14, 2019 swarm off Vancouver Island was first reported to be a magnitude 4.8, later upgraded to a magnitude 5.3. Although only 2 earthquakes were reported, which is too small to be considered a swarm, there were at least 28 other earthquake events I was able to detect using P wave cross correlation and studying the characteristics of the events themselves. To continue this post, please click the title or "read more" if you have not done so already.

As stated above, late in the UTC day of February 13, 2019, a strange swarm started to break out off the coast of the northern tip of Vancouver Island. The majority of the seismicity as of late has been centered around two areas: near the end of the northern section of the Cascadia Subduction Zone (CSZ) and at the end of the southern section of the CSZ. What this means is beyond me, at least for right now. Below is an illustration, put out by oregon.gov, of the Cascadia Subduction Zone:

If you don't know what the Cascadia Subduction Zone is, then please CLICK HERE.

The image above shows the likely swarm epicenter and the closest seismic station: HOLB in the CN network. Now remember the bottom of the ocean can be very volcanic. Though it is likely these are caused by tectonic stresses, you should never completely rule out some type of volcanic or deep magmatic activity.

Now swarming has occurred in this location before. A few months ago there was actually a swarm of many events, including multiple M6.0s and one that almost reached M7.0. Please CLICK HERE to view the post dedicated to that large swarm on October 22-23, 2018. This swarm I am detailing in this post contained approximately 31 earthquakes of many different sizes from around 22:40UTC February 13, 2019 to about 19:34UTC February 14, 2019. That was determined by using the program WAVES, data collected from nearby stations, and cross correlating their possible P wave arrivals.

Below I will first show one of the more energetic parts of the swarm and then I will show the helicorder image for station HOLB. It shows some of the events that transpired during this swarm, including the 2 reported events. Then I will show the USGS event pages for the 2 reported events, including their custom made 3-plot images. After that I will show about half of the events within this swarm via my custom 3-plot images and a slideshow. Remember to always pay attention to chart labels and any captions beneath any images.

Now I am going to show you many 3-plot images of many events during this swarm (approximately half of them). There are 15 images within the slide show below. All plots are labeled and all times and dates, as usual, are in UTC format.

Welcome to the first post on another new page just recently added to my website! This first post will deal with a very energetic, rapid fire swarm that struck east of Los Angeles on February 7, 2019. This swarm seems to be similar to the ones seen at West Thumb Lake in Yellowstone from time to time (CLICK HERE for that). This swarm also occurred very close to Lavic Volcanic Field and the Pisgah Cinder Cone. As usual, please click the title of this post or "read more" to continue...

First off, the image first posted (in the intro) shows the location and some information about Lavic Lake Volcanic Field. You can see I also marked where the swarm occurred. The image directly above shows the location of the earthquake swarm in regards to the 2 closest seismic stations and the Pisgah Crater Volcano (cinder cone). This whole area still is potentially volcanic and most likely will see another eruption someday. However it is likely the eruptions in this area will be of traditional lava flows. Although tephra and ash have the possibility of being ejected, lava effusion is the most likely outcome.

The data and info in this post pertains to the events that transpired just to the east of Pisgah Crater in California from 00:00UTC February 7, 2019 to 5:26UTC February 8, 2019. The swarm saw 63 reported earthquakes during the time period just stated. A few others occurred after this time period, but it seems the swarm is calming. However another update will be issued if another swarm occurs in this area.

Now this swarm in question occurred just east of the Pisgah Cinder Cone and Lavic Lake Volcanic Field (intro image). Please CLICK HERE if you wish to learn more about Lavic Lake and CLICK HERE to learn more about specifically Pisgah Cinder Cone. Also, please CLICK HERE if you wish to visit the USGS EQ map detailing all reported events that occurred within the location and time period stated above.

This interesting earthquake swarm carried a good amount of energy and can be characterized, during many moments, to be a rapid fire swarm, much like what is seen around West Thumb Lake at Yellowstone from time to time. This rapid fire swarm seems to be more within the lines of a small intrusion of magma, but do not hold me to that. It is possible this was tectonic, but the characteristics of the swarm, including how fast the events occurred, point out that this was most likely some type of rock breaking event. Of course hydrothermal activity could do this as well, however magma is a more likely culprit for this area (as is tectonic activity).

First, there was a small burst in seismicity lasting 4 minutes that contained 4 micro-quakes at about 1:04UTC Feb. 7. Then another episode of seismicity occurred from 7:16UTC to 9:55UTC on Feb 7 that included a total of approximately 55 earthquakes. Then, the main burst of seismicity started at about 14:16UTC and lasted until 20:44UTC, on Feb 7 as well. The total for the main burst, including events too small to be reported, was around 190 earthquakes of all sizes. The rest of the seismicity from 20:44UTC Feb 7 to 5:26UTC Feb 8 contained around 80 earthquakes of all sizes. Many of the events occurred in pairs and episodes, instead of stretched out over a period of time. Again, this earthquake swarm is categorized as a rapid fire swarm.

Altogether, for the entire time period stated at the beginning of this post, approximately 329 earthquakes occurred with only 63 of them being reported! Many were most likely not reported due to the lack of strong amplitudes and the lack of a dense seismic array of stations. The estimation above may be off just a tad, I wouldn't be surprised, but it is pretty close! Again I used data from surrounding stations in the program WAVES to cross correlate P wave arrivals.

Below I will show alot of data in regards to this swarm. I will first show the helicorders for the 2 closest seismic stations and will put them in slideshow format: NBS and RAG, both in the CI network within the SCEDC database. Then I will show the USGS event page and 3-plot image of the largest earthquake within the swarm. Afterwards I will show a strange low frequency event, the 3-plot images to the fastest parts of the swarm, and the rest of the seismic plots will be shown in slideshow format (in 2 slideshows) at the bottom of the post. Remember I am not able to show you ever single event within the plots below. However I will try my best to show most of them! The last 2 slideshows at the bottom of the post contain 24 3-plot images.

Remember to always pay attention to chart labels and any captions beneath any images!