# The number of large earthquakes this month

Hi,everyone,

I notice that there were only two large earthquakes happened.One happened in Indonesia（2021-06-03 M6.1）, the other happened in Kermadec Islands（2021-06-20 M6.5）.This month’s earthquake frequency is at a low level.

Usually, there are about 10 earthquakes of magnitude 6 or above in a month. Of course, most of them are earthquakes of magnitude 6.

So,my question is will this increase the risk of large earthquakes around the world？If so, how will the influence degree be? Will the last week of June become dangerous？

The following is my statistics of the number of earthquakes with magnitude 6 and above per month in the first half of the year：
January（12），February（16），March （20），April （14），May（13）June(2?)

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Hi Wilson,
The number of earthquake of magnitude >= 6.0 is variable from one month to another, even though one can expect tenth of eathquake in the this range of magnitude per month, it could be less. For example I checked our DB in June 2018, there were only 4 earthquakes of magnitude >=6.0. And on top of that, the month is not over yet
It is impossible to predict what’s going to happen by the end of the month or the rest of the year, or even if one can expect a larger one. We cannot predict an earthquake.
I hope it help,
best regards,

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Recently, I’m sorting out the number of earthquakes in recent years and making it into a table. It should be completed soon. The number of earthquakes of M6, M7 and ≥ M8 has an unclear rule in a certain period of time, which will be more obvious in the table.
I will send out the form after I finish it. I’m look forward to communicating with you again.
Best wishes

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Look forward to the table, but not sure that the magnitude bands are actually relevant (they are arbitrary?). Maybe a scatter plot of magnitude against time would reveal a more significant categorisation / banding, or possibly a smooth spectrum with no gaps? In addition to magnitude, I think there may be patterns in location of the quakes too, concentrated on southwest-Pacific / west Indonesia, west coast South America, Caribbean etc, but I haven’t formulated any rules for this yet - it is just qualitative. The more exploration of the data the better I would say! Rgds Dave

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I admit that the statistics of earthquake magnitude are vague, because to tell you the truth, I don’t know what to look for. I just set a time limit, such as one year, and then count the number of earthquakes, but it’s unknown what the number is related to. But it shows some regularity.

These statistics are attractive, including the scatter plot you mentioned and so on. I saw a video about the statistics of the East Japan earthquake data in 2011. The author took the longitude line as the abscissa and the focal depth as the ordinate. He counted the earthquakes within one year after the main earthquake and made a chart. The dense points on the chart (each point is an earthquake) formed a beautiful arc, like a logarithmic function of a > 0, It clearly shows the subduction of the Pacific plate into the North American plate off the coast of East Japan.

I think this is wise. We can’t see the earth’s interior with naked eyes, but we can reconstruct it with data. After all, the information comes from the earth’s interior， It is the “voice” of the earth.

I have finished my chart. I want to do more analysis, but my ability and time are limited. I will send the chart below. I hope you can enjoy it and find something new.

best regards

Hi，everyone，I looked up the USGS database and made quantitative statistics，now I’ve finished my chart. I hope you like it.

The first is the quantity chart. The abscissa is the year, and the ordinate is the number. I have separately counted the number of earthquakes of M6, M7 and ≥ M8 in each year, which is a total of three charts. There is also a total plot (≥ M6).

Then there is the frequency chart. My method is to divide the number of days by the number of times (366 days or 365 days / times). For example, the frequency of M6 in 2001 is equal to 3, which means that there will be an M6 earthquake every three days in 2001. Of course, this is a statement of probability, not once every three days.And so on, the M7 frequency of 2011 is equal to 26.1, meaning that the M7 earthquake occurs once a month (26.1 days) this year.

Therefore, the higher the vertical scale value in the chart, the better. Because in probability, it means that the interval between two large earthquakes is long, in reality, it means that the number of large earthquakes in this year is less.

The above is my chart, I hope you like it and have a good time！
Yours sincerely

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Hi Wilson,
That’s a nice piece of work, congrats
cheers,

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Thank you , jul, that’s very kind of you to say so!

Hey Wilson, I thought that may interest you: Geologic activity on Earth appears to follow a 27.5-million-year cycle, study - Tech Explorist

even though it’s quite a different time scale you’re looking at

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Sorry it has taken so long to reply to this. The charts are indeed fascinating, but I don’t detect any obvious trends over the selected timescale or within the magnitude bands over a year (this is just by eye, not mathematically tested). On thing that seems obvious is that the number of M>6 is not totally random, but always >75 and <200, why should that be? There may also be a similar argument for M>7, always >0, but never more than 25? Something happens between M7 and M8 (and presumably M>8) as at least some years have no very large quakes at all, but then there are no 2 year gaps (thanks this year to the recent big Alaska quake!). Is this telling us something about quake mechanisms and how long it takes to build sufficient strain to create a very large quake. Might that also suggest an upper limit for M for a quake due to plate tectonics? These data are all global of course, so it still doesn’t give any hints about a quake happening at a particular place on a particular day. Maybe more localised monitoring of smaller sized quakes (but still large enough to not be drowned out by noise) would give some further clues? I think I read somewhere that parts of the San Andreas and related faults are monitored for movement and those parts that are stuck for an extened time at the ones people might worry about most? For faults driven by tectonics, little and often quakes are good! Better stop there, I am getting very speculative I fear Keep up the good work Quake-Watchers

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Just to note that today my check on the global M>4 map showed only 17 quakes - as far as I recall, that is the smallest number in a day ever (‘ever’ being since I started looking at this site about 2 years ago?!). I think this is pretty close to the smallest possible number M>4 per day, but I can’t prove it or explain it in more detail

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I checked the database and found that there were 19 earthquakes with magnitude ≥ 4 on October 28. Then I inquired about the number of daily earthquakes in October. You are right. The 28th is the lowest number of earthquakes in October, and the 20th is also. But in terms of energy, I think the 20th is lower, because the same is the 19 time, However, there were few M5 earthquakes and many M4 earthquakes on the 20th, and 28th is the opposite.

And I haven’t had time to check the data of the whole year and the past. There are too many data, so I don’t know whether the 19 times are the least in the whole year or the least since records.
Unless there are earthquake swarms, volcanic eruptions, or aftershock sequences of large earthquakes, I don’t pay much attention to earthquakes with too small magnitude. Their energy is too small. The energy of a magnitude 6 earthquake is about 900 magnitude 4 earthquakes! Of course, some small earthquakes may be foreshock hints of a large earthquake, but these earthquakes are concentrated in a certain area.
So I don’t know what the data on the 28th can tell us, but thank you for your careful observation and tell us this discovery.

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And we had a 6.1 magnitude earthquake in the South Sandwich Islands two minutes and fifty seconds after the end of October …

And two times M5.0 at 00:00 UTC and 03:07 UTC.

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Thanks Wilson, I really like your meticulous and detailed chart for October! I accept that my choice of M>4 as a threshold for tracking / assessing daily quake numbers is arbitrary - it is simply the threshold used by the global map on the EMSC site! However, my central theory is that due to the current status of plate tectonics on Earth, there will always be some relatively large quakes every day - what the actual threshold is (M>3.5, M>4, M>4.5 etc) I don’t know / can’t establish and I don’t know what the true minimum is - although n=17 seems close to it so far! Likewise there is a max n, for big quakes: as most swarms are made up of quakes below the M>4 threshold and it takes longer than one day for strain to build enough for multiple big quakes in the same place (strictly perhaps I should exclude after-shocks from ‘daily n’ as they are really just part of one event?). I don’t have the knowledge or method to model or otherwise test the theory further at this stage, but it is fun (for me anyway ;)) to check almost every day to see if the number of quakes still fits my ‘theory’! Thanks again for your time and effort in putting together the fascinating data. Best rgds Dave

South Sandwich Islands an interesting tectonic setting, I would love to visit! Quakes there very often much larger than the numerous daily events seen elsewhere, but not as big as ‘regular big ones’ around Kermadec region and Aleutian / Japan arc? All good for further theorising…

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