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I am a novice here and I really appreciate the graph of magnitude >7 earthquakes related to 11(22)yr solar minimum cycles.

I was wondering what the correlation would be (if any) if we changed the window to consider 7.5 and above quakes over the past 400 years (assuming such data is available and reliable)?

Also, some discussion about the difference between Solar Minimums and Grand Solar Minimums would be helpful. In other words are there set periods in which Solar Minimums are even smaller than usual (Grand Solar Minimums) and do really large earthquakes tend to happen during these periods?

Thank you for your interest.

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    $\begingroup$ The data you're looking for doesn't exist. The Richter scale was invented in 1935, the Wood-Anderson seismograph dates from the 1920s, and subjective scales like the Rossi-Forel only date to the late 1800s. Even a simple chronicle of "great earthquakes" is incomplete prior to the 1800s because of a lack of people recording earthquakes in places like the East African rift or New Zealand. $\endgroup$
    – Mark
    Jun 7, 2018 at 7:23
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    $\begingroup$ are you asking if the radiative output of the sun changes the gravity of the earth-moon-sun system? it is like saying a lightbulb gets heavier when you turn it on/off. $\endgroup$
    – trond hansen
    Jun 7, 2018 at 7:52
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    $\begingroup$ This seems to be an X-Y problem asking for data to prove/disprove the relation between earthquakes and solar activity. That question has been asked here already. Asking for earth science data here is fine, but can also be done on Open Data, and several questions about erathquake data exists there. $\endgroup$
    – Jan Doggen
    Jun 7, 2018 at 15:24
  • $\begingroup$ And if you go hunting on Open Data for sunspots you find this answer pointing to this resource, which may help you further $\endgroup$
    – Jan Doggen
    Jun 7, 2018 at 15:25
  • $\begingroup$ @Mark In addition the lack of people making records in East Africa and New Zealand during those centuries, let's not forget Antarctica and the mid-ocean ridges. $\endgroup$
    – jeffronicus
    Jun 8, 2018 at 15:30

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As others have pointed already in the comments, there is no earthquake data extending that far back. But we do have data for the last century. In a similar way to my answer to this question. Here I've plotted the yearly count of all of the earthquakes worldwide from 1900 to 2018 of magnitude greater of 7,7.5, 8, or 8.5 found in the USGS Earthquake Catalog that span back to year 1900 (bars), along with the total number of sunspots per year from the Sunspot Index and Long-term Solar Observations (red line). Here is the resultant graph:

enter image description here

As you can see, there is not any significant correlation between frequencies of large earthquakes of any size and the solar activity. The solar record shows the well-proven 11 year solar cycle (actually it's a 22 year cycle with two similar halves). On the other hand, the earthquakes show no clear pattern.

Unfortunately, for the grand minimums like Maunder and Dalton's solar minimums we do not have a reliable earthquake record. Nevertheless, given that EVERYTHING we know about physics and earthquakes suggest that there is NO mechanism by which solar activity could possibly influence earthquakes. And provided that there is no evidence of such correlation in the 100+ years of the instrumental record. There is absolutely no reason to believe that such correlation exist. The answer to this question should be informative too.

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  • $\begingroup$ Interesting, it almost looks like a 40 year cycle in the major earthquakes. Though I've certainly learned to be wary of seeing any pattern visually... $\endgroup$
    – JeopardyTempest
    Aug 11, 2018 at 13:12
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    $\begingroup$ @JeopardyTempest If you cherry pick a few decades you can definitely find a correlation, but if you see the whole picture it vanishes. Also note that earthquakes do have a typical recurrence time, and there is only a handful of plate boundaries capable to produce very large earthquakes, so of course some times the periods can become in sync, but that's just a coincidence and given that they are independent systems they will soon go back to be out of sync. $\endgroup$
    – Camilo Rada
    Aug 11, 2018 at 17:11

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