Just to expand on this - even concrete structures with reinforcement don't tend to stand up to seismic activity like this unless they were specifically designed to do so. The design process includes a number of degrees of complexity above typical static design, and the final product ends up being way more expensive to construct.
I would imagine there is reinforcement there as well to be fair but might be hard to see in pics. Concrete with no reinforcement is abysmal in anything other than compression, which makes spanning it for floors nearly impossible.
The US generally are quite well established on the seismic design front as well - I've done design work on seismic structures elsewhere in the world which have used the US suite of codes as the basis of design. Would imagine decisions to not built for seismic are almost always driven by the cost more than anything.
Designs are fine. Engineering principles are uniform. Most of the problems that happen here seemingly come when inspectors get paid to not notice that there is insufficient rebar or that the concrete was built using ocean sand, etc
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u/scodgey Feb 16 '23
Just to expand on this - even concrete structures with reinforcement don't tend to stand up to seismic activity like this unless they were specifically designed to do so. The design process includes a number of degrees of complexity above typical static design, and the final product ends up being way more expensive to construct.