Update:
I tracked my disasters through the Ancient Era on Deity with Trung Trac. I played up to turn 136.
I had floods in the exact same spot on turns 15, 17, 31, 35, and 36.
I forgot to track my disasters from turns 37-125.
Then, I had volcano eruptions in the exact same spot on turns 126, 127, and 131.
This is with the natural disaster setting on Light.
This is why the disasters feel repetitive and like too much even with the natural disaster setting on Light. I'm getting the same damn disasters, 3+ times in a row, within a few minutes of each other.
As soon as I repair the tiles from one disaster, I get the same disaster again.
Firaxis, this is too much. Please fix it. On the Light setting, disasters should happen maybe 4 or 5 times per era in your whole empire. Not this!
I think appropriate disaster frequency levels would be:
Catastrophic: About once every 5-10 turns on average.
Normal: About once every 15-20 turns on average.
Light: About once every 25-30 turns on average.
Also, the same disaster in the same location should not happen more than once or twice per era on Light, three or four times per era on Normal, or five times per era on Catastrophic. It should never happen multiple times within the same 5 turns!