In the recent earthquake in Turkey you see modern buildings crumble or pancake but a 500 year old mosque seems to be survived with only minor damage.
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Answer: earthquakes of different magnitude shake the earth at different frequencies. Buildings (and our structures) can have frequencies at which they inherently have surprising stability or massive instability. These “resonance frequencies” can be dependent on the shape, weight distribution, materials, and much more.
It’s likely that some surviving buildings in Turkey happened to have a unique stability at he frequency of the recent earthquake – or the converse – the downed buildings had a unique vulnerability to the frequency experienced. It’s quite likely that an earthquake in the same location but with different soil mechanics or magnitude could have collapsed a different set of buildings (leaving some that collapsed in the first scenario, and toppling some that stand today).
The challenge of engineers who “earthquake-proof” buildings is to have a building that has none of those highly unstable resonance frequencies, typically by putting “shock absorbers” at the base, which makes the building’s naturally unstable frequency lower than what earthquakes produce.
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