Central Croatia is located in a monster valley, located in compressive tectonics. The whole Mediterranean basin is closing, creating the Alps and surrounding mountain ranges. The Croatia mountains are moving with a sliding thrust, which has both strike-slip and compression.
Each monster zone around the world has about a one in 500 chance to light up with an M8 or 9. That means that each year, Fate rolls a 500 sided die for each zone. One side is painted red. If the red comes up, then KABOOM!
If there is something that looks like a foreshock, as with the recent earthquake, then the die is 100 sided for most areas. If the Fish calls it, then the die might go to 20 sided. All of this is fairly irrelevant for day-to-day life, but is good for planning purposes.
If the Big One rolls up, then we are looking at a PGV of 1-2 m/s on the valley soil and hanging wall. This is enough to throw rocks as with Kern County 1952. No building can take this, yet if you are on the footwall rock, then it is only a few centimetres per second.
If you want to build something that will survive, then you need tremendously deep foundations. I doubt that anybody has done that. Might not help with the giant boulders rolling down the mountains.
ps. I define monster zones as that which needs large earthquakes to maintain its form. Thus, we have very smooth subduction zones and then we have sharply defined mountain valleys. All these zones would fill in and become ragged, if not for huge earthquakes. Once the earthquakes stop, then everything becomes smooth and boring.
pps. and as a great Christmas present from the fish, the die goes back to 500 sides in a few months.