[PvK]

Xietor, you may be right that it's worth investigating. My contribution though is I've been playing several Luck-dominion nations in various games, and I only remember one earthquake in an extremely long time. Since I don't know of a spell that directly causes an earthquake, my only other thought (besides that repetition stands out when it happens) is it could be some combination of your particular scales and/or your nation.

Another theory is maybe the Dominions random number generator tends to get into patterns sometimes. I know it seems like sometimes I get several heroes on the same turn who all get the same heroic ability, and in one game I have had a huge number of "found magic items in tombs" events.