Do Solar Flares Cause Earthquakes?

This shows the what wavelengths of electromagnetic radiation can penetrate Earth's atmosphere and what wavelengths are stopped by the atmosphere.

We have been getting a number of questions and comments lately regarding the possible relationship between solar activity and geological activity, such as earthquakes and volcanoes, so I have decided to look into the matter in more detail.

First let us pose the science question we wish to answer: do solar flares cause earthquakes?

Note that this is more specific than asking ‘is there a relationship between solar activity and earthquakes?

 First of all, solar activity can mean flares, or coronal mass ejections, or bursts of solar wind. Here I will focus only on flares, but do bear in mind that flares and CMEs often occur in tandem. Secondly, we are asking if flares CAUSE earthquakes; not whether a LACK of flares cause earthquakes. If flares do indeed cause earthquakes then we would expect to see a positive correlation between flares occurring and earthquakes occurring. If a lack of flares causing earthquakes, then we would expect a negative (or anti-) correlation.

For this experiment, I have downloaded data from all known earthquakes from 1980 to the present day. This data is publicly available from the United States Geological Survey website (USGS). Here I must point out that I am not a seismologist – I have merely gathered together the dates and magnitudes of all known earthquakes greater than 4 on the Richter scale from the past 30 years. A list of all the solar flares from the last 30 years is also available from NOAA’s National Geophysical Data Center (NGDC). Below is the plot I made which shows the occurrence rate of both solar flares (in blue) and earthquakes (in red). (Anyone with a basic understanding of Excel, a little curiosity, and a bit of patience, can try this for themselves.) You can see that solar flares come and go with each solar cycle (approximately every 11 years), whereas earthquakes appear to occur continuously, with no obvious pattern. There are large (magnitude>7) earthquakes both at solar maximum and solar minimum. This to me would be evidence enough that flares and earthquakes are not related. But let us go a step further. What would something that IS correlated with solar activity look like?

The occurrence rate of both solar flares (in blue) and earthquakes (in red). (Click on Image to See A Larger Version)

What would something that IS correlated with solar activity look like?

For the next plot, I have gathered together data on the appearance of sunspots over the same 30 year period (; I happen to have access to a lot of solar data!). By overlaying the occurrence of solar flares on this plot, we can clearly see that the number of flares rises and falls with the number of sunspots (the orange curve), again every 11 years or so. I would call this a pretty strong case for proving that flares are in someway related to sunspots (which of course we know they are, as we can see flares occurring in regions of intense magnetic field on the Sun).

The occurrence rate of both solar flares (in blue) and sunspots (in red). (Click on Image to See A Larger Version)

I have also been looking at data on ionospheric disturbances here on earth as part of my own research (again, this data is publicly available via the Stanford University website I selected a day in which I knew there was significant solar activity (in this case, 18 February 2011) and plotted the solar activity for that day (top panel) against the corresponding changes in the upper atmosphere above Austria (bottom panel). This clearly shows that at least five of the flares that day (denoted by the vertical dashed red lines) had a direct impact on the ionosphere. Again, this suggests a causal relationship between solar activity and atmospheric disturbances; something not seen in the earthquake data.

The flare solar activity for 18 February 2011 (top panel) plotted against the corresponding changes in the ionosphere above Austria (bottom panel).

But these are large-scale statistical studies.

What if there was one ‘perfect solar storm’ that happened to slip through the net? Would that then have any geological effects? Well, what is a solar flare exactly?

The data I have used in the above plots are from X-ray sensors onboard the GOES series of satellites. So flares are essentially just that; increases in X-ray emission (and sometimes gamma-rays). There is, of course, increased emission from across the spectrum: radio, optical, UV, and infrared. Thankfully, the Earth’s atmosphere protects us by absorbing the vast majority of this radiation, as shown by the plot of ionospheric disturbances above. The only solar emission that makes it to the surface is visible light that we can see with our eyes, and radio emission (see figure below). So barely any of this X-ray light makes it through the atmosphere, let alone to beneath the surface to where earthquakes occur. Similarly, CMEs are essentially clouds of charged particles which get deflected by our magnetic field and rarely make it to the surface. And given that the Earth’s magnetic field has a strength similar to that of a household fridge magnet, any fluctuations caused by a CME impact cannot influence the motion of tectonic plates which carry entire continents!

This shows the what wavelengths of electromagnetic radiation can penetrate Earth’s atmosphere and what wavelengths are stopped by the atmosphere.

Of course, there are more sophisticated data analysis techniques and correlation tracking algorithms available compared to that which I have presented here. So if you feel that my rather simplistic approach has failed to reveal a potential relationship between solar and geological activity, then I urge you to sift through the data for yourself. This is how science works, which is why I have included links to the pages where I obtained my data so you may repeat the experiment for yourself if you choose, in order to verify or refute my conclusions. But simply noting that a solar flare and an earthquake occurred together within a short time frame does not imply that one caused the other. In the words of renowned astronomer Richard Carrington, “One swallow does not a summer make”.*Finally, as solar activity continues to increase during the rise of the current solar cycle, expected to peak around 2013, here is a statement from the USGS themselves on whether earthquakes are really on the increase or not as well (

We continue to be asked by many people throughout the world if earthquakes are on the increase. Although it may seem that we are having more earthquakes, earthquakes of magnitude 7.0 or greater have remained fairly constant.

A partial explanation may lie in the fact that in the last twenty years, we have definitely had an increase in the number of earthquakes we have been able to locate each year. This is because of the tremendous increase in the number of seismograph stations in the world and the many improvements in global communications. In 1931, there were about 350 stations operating in the world; today, there are more than 8,000 stations and the data now comes in rapidly from these stations by electronic mail, internet and satellite. This increase in the number of stations and the more timely receipt of data has allowed us and other seismological centers to locate earthquakes more rapidly and to locate many small earthquakes which were undetected in earlier years. The NEIC now locates about 20,000 earthquakes each year or approximately 50 per day. Also, because of the improvements in communications and the increased interest in the environment and natural disasters, the public now learns about more earthquakes.

According to long-term records (since about 1900), we expect about 17 major earthquakes (7.0 – 7.9) and one great earthquake (8.0 or above) in any given year.

* Mr. Carrington made this reference after observing the great solar flare of 1 September 1859, and then noting that the magnetometers at Kew Gardens had gone haywire a day later “as if the earth had been struck by a magnetic fist”. We now understand that this was due to a CME impacting the earth’s magnetic field, but at the time Mr. Carrington was urging caution in drawing a direct comparison between the two phenomena without further detailed analysis of the data: just because you see a swallow one day, it does not mean that summer has arrived. 


  1. Hey Ryan,
    Of course I agree with you that earth quakes are not a result of solar activity :).
    But, out of curiosity, I wonder what the first plot would look like with the earthquake data binned in some way. Perhaps if you weight the earthquake data by magnitude similar to flare index (F=sum(Nc)+10*sum(Nm)+100*sum(Nx)) and plot as a line, instead of scatter plot, it might be even more convincing that there is no correlation. And then maybe smooth by 6months or a year…
    Nice post anyway. Its about time someone put these rumours to bed! We have gotten a number of emails on SolarMonitor about the same thing.
    See you at the next conference!

  2. David Soroa says:

    Hi. First of all I want to thank you for your effort. I´ve got a question about your work (note that I´m a guy that have´s no idea at all, just a novice): ¿how many of those flares and CMEs were Earth directed?. That´s an interesting point to study.
    However, it seems evident that there are always earthquakes and the sun has a clear cicle, so I supposse that it doesn´t matters at all if the flares & cme´s were earth directed…
    Thank for share!
    (Excuse my poor english)

  3. John Howard says:

    Thanks for an interesting article. I note one minor error: the caption beneath the earthquake/solar flare graph mistakenly labels the red as sunspots, though the graph itself says red is earthquakes.

  4. calexyoung says:

    Thanks for catching that John! I found a problem in the html and it should be fixed now.
    Alex Young

  5. Richard King says:

    Thank you for a wonderful article!

    However, David Soroa is correct… the correlations of all earthquakes and all solar flares detected should be zero as is the case in your graphs… it the earth directed solar flares above some critical size that is the which is the correlation of interest.

  6. Emma Cunningham says:

    Thank you for this excellent article. My mother watched a documentary alleging that earthquakes were caused by solar flares, and that they would therefore increase in number and strength throughout the 2012/2013 period. She was alarmed (we are in Christchurch, NZ), and I was glad to be able to show her some data to disprove the correlation. You helped a very nice lady sleep at night, so thankyou!

  7. marc A says:

    Please explain why the USGS erases and down grades earthquakes over the last seven or eight years. If you take a survey you will find many of your readers substantiating what I am claiming. I have seen quakes go from a 6.3 down to a 5.8. If you do a thorough analysis, you will find that this practice has become increasingly evident. This was not the case twenty years or so ago when the presence of a looming heavenly body discussed by Dr. Gerry Neugebauer in the December 31, 1983 issue of the Washington Post, was first noted. In fact this is the only time that this heavenly body was noted by Dr. Neugebauer in this or any other publication.

    In the interest of the truth,
    Marc A.

  8. Dr Jane Wright says:

    Once again science fails again, clearly unable to answer questions but presented with a logic based research criteria full of useless charts dodging the question at hand. We see a very well constructed one side perspective twisting the question into other questions that were not asked and using a flawed perspective and limited understanding to present false information. Clearly there is a strong relationship every seismologist with an open mind knows about this but unfortunately not comprehended by these solar “experts”, who admit into having no knowledge of geology or seismology.

    Its obvious this “sun team of solar facts and weather” are experts in manipulation from what I can gather. The Question was do flares cause earthquakes? And this is the best presentation offered by people who are put in places to be of service to humanity? For me this is an insult to the intelligence of all of us who genuinely want answers.

    The solar team know what induction means? Obviously not as its not presented in the article. The article itself admits to not being qualified in earthquakes / seismology so its clear you do not have a full perspective or knowledge base to draw upon and it showed in this poorly presented work.

    Geoeffective means storm causing for us here on earth however mysteriously not even mentioned in this research. What about Geomagnetic storms?, given the fact we have a delay of 2-3 days where space weather influences the earth’s magnetic field. Somehow the obvious is missing in this pitiful research document. IMF disturbances, where is this information. Not even considered apparently.

    Solar Flares produce coronal mass ejection’s, from these we have geomagnetic storms, solar flares produce proton and electron events, solar flares produce radiation storms. We can go on and on and on with what the sun does.

    How about answering this question.

    Why do solar storms cause geomagnetic storms, what effects to strong solar storms have on the earth, and finally what are space-quakes. A term used by scientists at NASA, What is a Magnetic Flux Portal and its influences here on earth. These questions you are “qualified to answer”

    And if you cant answer the above questions you should remove this disgraceful article immediately.

  9. SolarIMG says:

    It’s possible changes in atmospheric density could allow atmospheric density to allow the plates to move .. There is also the ionization and plasma that enters in the poles (and neutrinos also!), that may be the energy transfer mechanism that changes the viscosity of the magma, creating lubrication effects.

  10. SolarIMG says:

    Also it’s important to note that it may be the CME, which takes several days to arrive and the field orientation of the cloud makes a difference in the geoeffectiveness… Some CMEs are more geoeffective than others, perhaps using the AP index may yield different results.

  11. […] E’ Ryan O. Milligan, un fisico solare del Goddard Space Flight Center della nasa. Il sito è Fonte: […]

  12. Diego says:

    Hello, excellent post! I am a seismologist at UCSD and I keep a mildly succesful blog in my native spanish about all things geophysics. I get this question quite a bit so I’ve written a little summary of this post and linked up to it. Also I ruthlessly stole one of your plots, I hope that’s ok with you guys. You can see the post here (

  13. […] y me queda mucho trabajo por hacer, pero si les interesa saber más los invito a visitar el blog ( Ocurrencia de erupciones solares (azul) y sismicidad […]

  14. DAILY SUN says:



  15. Lorena Remmell says:

    Great article, but if this has been a long-standing question why hasn’t anyone in Geophysical Science or NASA conducted a detailed research of this topic? Or have they done research and not publish to the public?

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  17. […] Lea más en el artículo Harriet Jarlett sobre Planet Earth Online , y los resultados de otro estudio ver al Dr. Ryan O’Milligan del artículo sobre […]

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  19. Dale Rice says:

    Hello, I found the article useful and reassuring. The question I have relates to Energy transfer to the Core of the Earth by a 5% closer apprach to the Sun in Winter than summer = a kind of squeezing of the planet due to the differntial gravitational pull in Nov-Mar period. Over time would the squeezing amount to energy loading of the core of the planet, causing expansion of Magma?

  20. Your method of telling the whole thing in this post is really fastidious,
    every one be able to easily be aware of it, Thanks a lot.

  21. David Ben Judah says:

    Hi, the reason I looked for a possible correlation between disturbances in the EMF and earthquake is that there has been claims that HAARP could be used as a weapon causing earthquakes by disturbing the EMF and or ionosphere. You research however does not give a conclusive answer for this question as HAARP theoretically could have a much larger EM output then a solar flare over any given point on or over the earth.

    So my question is, how great a disturbance in the EMF is necessary to cause an earthquake? What would the required output be to cause such an effect? And if you have access to one or more of these facilities specs, do any of the HAARP facilities have sufficient output to in theory to be the cause of such an event?

  22. K. Sasikumar Raja says:

    Even though, I believe that there is no relation between solar activity and earthquakes.
    One doubt is,
    Since it is mentioned that, the number of seismic stations are increased and detected more earth quakes. Probably our sensitivity of detection of weak flares are not there. So some how these two has to be matched.

  23. DOM says:

    Have addressed the problem in the right way, but then you’ve hijacked on x-rays & CME.
    Surely cme & x-rays can be measured, but they are only effect made, how can you measure the light energy that is directed towards the planet?
    Let me explain, you have not considered this simple device:

    the sun is the only engine of the whole solar system, source of light, heat and life, but also because of not only earthquakes and even volcanic eruptions (it would be interesting to compare these data).

    and then there will be only one swallow make a summer!