A 1967 study published in the Earth and Planetary Science Letters found:
Solar activity, as indicated by sunspots, radio noise and geomagnetic indices, plays a significant but by no means exclusive role in the triggering of earthquakes. Maximum quake frequency occurs at times of moderately high and fluctuating solar activity. Terrestrial solar flare effects which are the actual coupling mechanisms which trigger quakes appear to be either abrupt accelerations in the earth’s angular velocity or surges of telluric currents in the earth’s crust. The graphs presented in this paper permit probabilistic forecasting of earthquakes, and when used in conjunction with local indicators may provide a significant tool for specific earthquake prediction.
A 1998 report by a scientist from the Beijing Astronomical Observatory, Chinese Academy of Sciences, also found a correlation between low solar activity and earthquakes:
It has been found that:
(1) Earthquakes occur frequently around the minimum years of solar activity. Generally, the earthquake activities are relatively less during the peak value years of solar activity, some say, around the period when magnetic polarity in the solar polar regions is reversed.
(2) The earthquake frequency in the minimum period of solar activity is closely related to the maximum annual means of sunspot numbers, the maximum annual means of solar 10.7 cm radio flux and solar proton events of a whole solar cycle, and the relation between earthquake and solar proton events is closer than others.
Mitch Battros theorized in 1998 that large solar flares affect Earth’s magnetic field, which in turn shifts the oceanic and atmospheric currents, which can cause earthquakes and extreme weather. As Battros summarizes his formula:
Sunspots => Solar Flares (charged particles) => Magnetic Field Shift => Shifting Ocean and Jet Stream Currents => Extreme Weather [including earthquakes, volcanoes, hurricanes or other extreme natural events]
Battros’ theories have been endorsed to one degree or another by:
Dr. Ernest Hildner, Director NOAA Space Weather Center
Dr. Tom Van Flandern, former US Naval Observatory Chief of Celestial Mechanics
Dr. Stefaan Poedts: Lead Scientist University of Leuven Center for Plasma Astrophysics
Dr. Ronald van der Linden, Director of Solar Physics Department of the Royal Observatory
Dr. Pål Brekke, Deputy Director of SOHO project- European Space Agency