"There seems to be a correlation between shortwave radio propagation and upcoming earthquakes."
"If real, what would be its physical basis?"
"Release of electric charges from the ground into the air."
"Not unreasonable... But after removing the effects from solar activities, correlation disappears."
"Then it must work the other way around, earthquakes are triggered by solar activities via the ionosphere or geomagnetism."
"Statements dreamed up by the utterly deranged."

There's even a wilder hypothesis that claims human-made electromagnetic pulses can induce earthquakes...