Quake Works FAQ and Support site documentation.
If you take the last 50,000 earthquake events (strong ones, any event magnitude 4.0 and greater) and compare their month of occurrence against 50,000 randomly generated months, it is not statistically possible to show a difference between the random and the real.
If you continue to test larger volumes of earthquakes (by their months) they will continue to look identical to random data… until you reach ~100,000 tested earthquakes. At this point the real data will start to behave differently to the random data; earthquakes will begin to "prefer" some months over others.
Once you go over batches 250,000 earthquake months, the statistical difference is strikingly apparent. The divergence will become only greater with larger tested volumes.
The Flux site details testing over 416,000 earthquake event timestamps, using months, hours other elements of time. At a batch volume of almost half a million tested records it is safe to say that it is highly improbable that earthquakes are randomly distributed through time.
This slow but steady increase divergence indicates that there is a subtle pattern, a very delicate influence effecting the occurrence of all earthquakes. All. Because this pattern is so subtle it can only be revealed by compiling and testing extreme volumes of earthquakes. If this extreme volume of aggregate data is distilled even further, the results indicate that the most likely culprit is the tidal forces of the Sun's gravity on the Earth's crust, also known as the Earth-tide.
The effect of the Earth tide is very slight, with the ground moving a distance measured in centimeters. This displacement can effect sensitive equipment, like GPS satellite stations, but largely goes unnoticed. But unlike ocean tides, the effects of which are apparent just on the surface, the Earth-tide deforms the shape of the planet, crust and all.
The phenomenon of the Earth-tide could be a subtle but powerful enough mechanism to effect the tectonic plates, and by extension, their earthquakes.