Why humans settle in valleys? Is a question you should ask
The question is why people build new on known dangerous places. The new is an important word. They do because the future is not priced in (make insurance mandatory?) and because of acts of corruption that actively promote/incentivize development in hazardous areas by rewriting zoning, repricing permits, rewriting saner policies.
Hard to build on the mountain, and the valley has transportation, easier to build, fertile land, food and water.
It’s very obvious why humans settle where they do (despite the risks).
Brought up there.
Every five or ten generations, different risk.
BTW, I can't build anything in half of my garden unless I also build huge concrete structures to anchor the terrain, which maybe would make matters worse. My house has been there for about 100 years, the other houses too, maybe it's stable enough but often they allow what's already there and deny anything new. Anyway, it's fine, I don't want to build something there.
No that is not my question at all. In fact I don't have a question, I have a position.
My position is that population density in many of these super dangerous areas is because of corruption laced government policies and practices. The government follows these policies in concert with builders because they can knowingly profit from endangering people (i) in dire straits, (ii) people who are not informed about magnitude of the risks.
In addition to that their corrupt practices distort the market prices so that people end up suckered. If these corrupt practices were to stop or reduce and better more people friendly policies were followed then these place will not become uninhabited but plausible less populated. If you look at my other comments on this story you will get more details of my position.
Some people are in such dire straits that they may still agree to stay in a hazard equivalent to living on Chernobyl lands. Some who are more fortunate would take other options should the government be doing their job.