Whether or not solar storms can trigger earthquakes is something that should not be that difficult to determine. However, even though that theory has been around for a while I have not seen any reports stating that the question has actually been answered.

One variation of the theory proposes that the storm energy can be strong enough to cause measurable heating in the fault zone rock layers. And I myself expect that even small amount of heating in a fault zone area where an earthquake was getting ready to occur anyway could push it over the edge and trigger the earthquake days, weeks, months, or even years before it would have otherwise.

If I remember correctly, I did see a report that said that some group in Europe is presently looking into this to see if that solar storm - earthquake triggering theory can be proved or disproved.