M6.8 Greece and M2.9 Montana Earthquakes 10/25/18

At 4:54PM Mountain Time October 25, 2018 (22:54UTC October 25, 2018) a very large M6.8 earthquake struck off the southern coast of Greece. It was very shallow for an earthquake of this magnitude so it really shook up Greece! This area is seismically active and does have large earthquakes from time to time. The largest was apparently a 7.3 on October 6, 1947. However what is interesting with this earthquake is that there was a smaller foreshock just before the 6.8. Also, about 3 hours later, a magnitude 2.9 earthquake struck Montana just about 20 miles northwest of Bozeman. I will show the helicorders first and then the seismogram/spectrogram plots for these different events. PLEASE CLICK THE TITLE OF THIS POST OR "READ MORE" TO CONTINUE!!!

---

M6.8 in Greece:

Hey guys! So first I am going to talk about the M6.8 earthquake that struck Greece and then I will move on to the M2.9 quake in Montana. On October 25, 2018 at 22:54UTC a very large M6.8 earthquake struck off the coast of Greece. As you will see in the image below, you can see the earthquake was preceded by one foreshock. A foreshock is like an aftershock except it occurs prior to the main earthquake, rather than after. A great example of foreshocks is the Japan 2011 mega-quake. It is well known that there were many foreshocks before that devastating quake.

After the 6.8, over a dozen aftershocks occurred with many more still occurring. It was quite strong! The depth of this M6.8 was 14.0km which is quite shallow for an earthquake of this magnitude. Now I will show you the helicorder for seismic station KEK which resides in the HL network in Greece.

You can see the location here of seismic station HL_KEK_HHZ_--. The red star is the location of the M6.8 earthquake. KEK is about 200km or so north of the epicenter.

Here is the SWARM-generated helicorder for station KEK in Greece.

Now I will quickly show two seismogram/spectrogram plots. As always, please pay attention to time period, frequency range, and amplitude count! Remember chart labels are very important and must always be read first before reading any data.

This was a foreshock. It was reportedly to be a magnitude 5.0 earthquake at 10km in depth. It occurred just about 30 minutes or so before the M6.8. At the time of writing this, 2:02PM PST 2018/10/26, there have been 26 aftershocks ranging from M5.2 to M4.0.

This is the seismogram/spectrogram plot of the main M6.8 earthquake that hit Greece at 14.0km in depth. Notice it lasted a very long time! You can also see the first aftershock right at the end of the plot (seen better on the spectrogram).

M2.9 Earthquake in Montana:

About 3 hours or so after the M6.8 occurred in Greece, a strong M2.9 earthquake struck about 20 miles northwest of Bozeman, Montana at a shallow depth of 1.0km! Personally I believe it was more like a 3.2 earthquake. Below I will show the location of the earthquake in regards to the two closest seismic stations, the helicorder for the closest seismic station (which would be station SXM), and the seismogram/spectrogram plot. Once again, I cannot stress it enough, you must pay attention to all chart labels first! Also pay attention to time period, frequency range, amplitude count, or any image captions you may see!

*Seismogram/spectrogram plots were generated using data obtained from IRIS and the MB network through the program SWARM from station SXM.

The USGS report for the Montana M2.9 quake. At the time of writing this, only 2 people reported feeling it. I do believe many more felt it though since alot of people do not report to USGS.

The location of the earthquake in regards to station SXM and BZMT. Yellowstone can be seen at the bottom of the image.

This is the custom made helicorder for SXM in the MB network. You can see the earthquake occurred after the teleseism arrived from the M6.8 in Greece.

This is the teleseism (large, distant earthquake) of the M6.8 that occurred in Greece. Again, this is from station SXM which resides very close to Bozeman, Montana.

Here is the custom made seismogram/spectrogram plot of the M2.9 earthquake near Bozeman, Montana. Note the dominant high frequencies go well beyond 25HZ!

Well that is it for now! Remember generating these images using data obtained from IRIS, and using the program SWARM, is ridiculously easy. It takes a few days to get the hang of, but once you figure it out you realize it is the best way to monitor seismic activity. Feel free to peruse my website here to discover the many different ways to monitor seismic activity. All of what I have learned, in regards to downloading/finding seismic data and analyzing it, has been put here on this website in many different pages. This is done to help others realize just how easy it is to do the things I am doing! Keep your eyes out for more blog posts. Thank you for your time and God bless!