Because you need to put it somewhere on this planet, not on some ideal parallel world planet. There are various potential hazards pretty much everywhere. The N

Because you need to put it somewhere on this planet, not on some ideal parallel world planet. There are various potential hazards pretty much everywhere. The NRC has looked at all these and they have given their approval https://www.nrc.gov/reactors/new-reactors/smr/nuscale/ser-open-items.html It's thousands of pages, covering all things you can imagine, and many, many things you can't. It's their job. They have looked into earthquakes, what dangers they pose, what mitigands the design has against them, and in the end they decided the design is safe. But if you want the actual details, you can go to section 19.1.4.8.1 Seismic Risk Evaluation in this document: https://www.nrc.gov/docs/ML2020/ML20205L410.pdf