Are there any seasonal or diurnal trends in earthquakes? Though I imagine it's unlikely there is any significant correlation because daily and annual temperature variation really only impact a fairly shallow layer of the crust, I wondered whether the actual data backs that up.  I could envision a few unlikely causes, such as the expansion\contraction, rainfall amounts, or crazy things like the little differences in earth-sun distance.  So what say you?
There is a slight tendency for earthquakes in coastal areas to coincide with higher gravitational attraction. In one study in Greece, earthquakes were 15% more likely to occur when the sun's gravitational pull was at a maximum. In general though, seismic-tidal correlations are very weak (but not zero).