Correlation between earthquakes and solar activity?

This headline seemed far-fetched to me, but it's in a respectable journal and the correlation does seem to be rather strong.

On the correlation between solar activity and large earthquakes worldwide

Quote:

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 > 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.

Correlation doesn't always mean causation of course, but this seems to be a very clear correlation and the correlation increases with the magnitude of the earthquake. Could there be something to this "reverse piezoelectric effect" idea?

via International Skeptics Forum https://ift.tt/323Ctpf