Well, for me-

As stated, nothing was destroyed but I did get the income halved messaged displayed.

Loyalty dropped from 144% to 106% for one turn.

Income in Venice, which was reduced to 2312, is back up to 3842 now.

So it definitely wasn't a point blank "half" slashing of income and loyalty as it stated, but it was a slashing.

Perhaps how early we are in the game still (this happened at like 1113 and it's 1115 now) accounted for this lack of any major penalty this time.

Does anyone know if Venice is specifically prone to recurring earthquakes?

I don't remember it being any major issue but as you all know- This is my first campaign in some time and I hadn't ever gone very deep with the Italians before.