On the correlation between solar activity and large earthquakes worldwide
Authors: Giuseppe De Natale
Vito Marchitelli
Claudia Troise
Paolo Harabaglia
Journal: Scientific Reports (2020)
Discipline: Multidisciplinary
Keywords: earthquakes; correlation mechanism; seismicity; proton density; velocity data
Affiliations: Scuola di Ingegneria, Università della Basilicata, Via dell'Ateneo Lucano 10, 85100, Potenza, Italy., Department of Mobility, Public Works, Ecology, Env., Puglia Region Government, 70100, Bari, Italy., Istituto Nazionale di Geofisica e Vulcanologia, Via Diocleziano 328, 80124, Naples, Italy., CNR-INO, Via Campi Flegrei 34, 80078, Pozzuoli, Italy., Istituto Nazionale di Geofisica e Vulcanologia, Via Diocleziano 328, 80124, Naples, Italy. ., CNR-INO, Via Campi Flegrei 34, 80078, Pozzuoli, Italy. .

Abstract:  Large earthquakes occurring worldwide have long been recognized to be non Poisson distributed, so involving some large scale correlation mechanism, which could be internal or external to the Earth. Till now, no statistically significant correlation of the global seismicity with one of the possible mechanisms has been demonstrated yet. In this paper, we analyze 20 years of proton density and velocity data, as recorded by the SOHO satellite, and the worldwide seismicity in the corresponding period, as reported by the ISC-GEM catalogue. We found clear correlation between proton density and the occurrence of large earthquakes (M &gt; 5.6), with a time shift of one day. The significance of such correlation is very high, with probability to be wrong lower than 10-5. The correlation increases with the magnitude threshold of the seismic catalogue. A tentative model explaining such a correlation is also proposed, in terms of the reverse piezoelectric effect induced by the applied electric field related to the proton density. This result opens new perspectives in seismological interpretations, as well as in earthquake forecast. 

Retracted: No

PubPeer comments:
 Is this paper missing a potential correlation not mentioned in the text?  As a final test, we wanted to check if the proton density catalogue is completely uncorrelated. We know, as stated above, that the seismic catalogue of strong earthquakes is non-Poissonian and internally correlated, so we have analyzed the proton density series to check if it were characterized by a white noise spectrum that would indicate an uncorrelated process. We simply computed the power spectrum, which is shown in Fig. 7 (**annotated below**); it is clearly very different from a white spectrum, presenting at least two sharp peaks. We performed such a computation on the longest uninterrupted time window that has a 405 days length. This evidence testifies that neither the proton density distribution is random. So, this definitively confirms that the observed correlation between the seismic catalogue and the proton density cannot be likely obtained by chance; because the likelihood that two quantities, each of them internally correlated, show a clear mutual correlation only by chance is negligible. ![] The two triangles indicate the fortnightly and monthly tropical (~sidereal) lunar cycles which could potentially reflect tidal forcing effects which conflate with the 27-day sun rotation cycle, as described here https: agupubs.onlinelibrary.wiley.com doi full 10.1029 2008JD010499 , 
 #1 I believe you want to say that these periods can be easily traded-off, when studying periodicity in seismic catalogues, with well known tidal effects (often associated to seismic triggering, due to the evidence of such periods in many seismic catalogues). If I correctly understood your question, I must answer: yes, you are right. We added such a consideration in the preliminary version of the paper, but one of the reviewers suggested to eliminate it, with the motivation that introducing this further argument would have required a specific, too long discussion. However, we are working also to identify, in the seismic catalogue, such effects, although, since monthly tropical and sidereal sun days are not constant it is extremely difficult to pinpoint a fixed period throughout the 21 years data base. , 
 #2 Thank you. To discriminate between the tidal and solar 27-day cycles is an interesting idea to explore further ! The impact the tidal factors have on angular momentum shifts on the solid earth and ocean are quite apparent from continuous measurements (see below) but not so easy to deduce from discretely triggered events such as earthquakes. ![] ,