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By repopulation, I refer to the time it will take until the geographic conditions in and around the impact structure are tame enough for civilization (this can be small nomadic camps, and need not be full fledged cities) to settle in the vicinity.

I am trying to fit such an event where an area is struck by a meteor, and is gradually resettled to some extent, over the span of some centuries (I am open to correct this timeframe if it must be); this event also has a profound impact on and is an integral part of the culture of the local area in the world. At the time of repopulation, technology is at the level as of the mid 20th century (1930's - 1950's roughly), and impact has occurred about two centuries ago, if not older. More than repopulation, it would rather be more appropriate to describe the settlement as a forward post. No agriculture takes place in the affected area, but mineral resources can be explored.(motivation behind the resettlement is not that pressing of an issue.)

I am preferably looking to use an impact structure with an approximate radius of 10-15 km, and without significant erosion (however it is not necessary for the structure to be in pristine conditions, like a lunar crater). The planet, in all aspects, is identical to earth. Although this might seem contradictory, but the intention is to not have this be an extinction event, hence the change in tag( I had a mental image of a turbo-bad nuclear explosion to be honest).

TL;DR, how long would it take for someone to start living again in a meteoric crater ?

Edit: changing the tag to science-fiction, as science-based does seem restrictive, creativity-wise, and added some information for additional context

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    $\begingroup$ See the Earth Impact Effects Calculator of the Imperial College, London. To make such a large crater the impact energy must be in the range of some 100,000 megatons of TNT equivalent; that's about 10 times the total nuclear bombs of the USA and Russia combined. Few people will be left to care about how long it takes for the crater to cool down. $\endgroup$
    – AlexP
    Commented Mar 24 at 19:27
  • $\begingroup$ You basically described as AlexP said an apocalyptic event. Your asteroid would almost be a kilometer in size. If that thing hits your planet resettlement of the area is the least of their worries. As they are all going to starve to death. If you really want a cool big realistic crater my advice just let it happen 1 Milion years or so ago which would fix a lot of issues. $\endgroup$ Commented Mar 24 at 19:52
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    $\begingroup$ Hello @Centroid, welcome to Worldbuilding. As has been pointed out, science is a harsh task master and with that science-based tag you have very few options. I suspect to continue with this idea you'll need to use narrative necessity. $\endgroup$
    – JBH
    Commented Mar 25 at 0:33
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    $\begingroup$ Very quickly. After world wars, central Europe was liveable in some years. (Communist block was still nearly unlivable but that was because the communists.) $\endgroup$
    – Gray Sheep
    Commented Mar 25 at 11:58
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    $\begingroup$ After a meteor strike, there would be no soil in the crater, perhaps not even anything that could be eroded into soil, and certainly no microorganisms that support crop life. It is likely that the soil would need to be blown in over centuries. Meteor Crater in AZ has 100 ft of blown in and eroded soil after 50,000 years. Secondly, there needs to be sufficient rainfall to develop the soil. $\endgroup$
    – David R
    Commented Mar 25 at 14:32

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The tag is a bit restrictive. Sometimes it takes the fun out of a story to be so realistic. let's address this from a perspective instead.

The Chicxulub impact north of South America is believed to be one of the extinction-level events in planetary history. It's worth thinking about this. It destroyed a LOT of species including (I believe) all of the big creatures. But life survived! It's 200 km in diameter. It's believed the impact put so much dust in the air that it blocked photosynthesis for two years and dust continued in the atmosphere for up to 15 years.

Your proposed crater is only 20-30 km in diameter. For the sake of argument (and easy math) let's assume the lower range. Your crater is 10% the size of the Chicxulub crater. Worldbuilding is often about simplifications, so let's assume 10% of the photosynthesis block time, 10% of the area it is blocked, and that the long-term dust is also in the air for only 10% of the time. That's 2.5 months of blocked photosynthesis, about 5 square km of affected area, and about 18 months of dust hanging around in the air.

How soon could someone repopulate?

What this simplistically means is that what you're proposing is not an extinction-level event. It could cover an area of approximately half the size of the United States to block photosynthesis for 2-3 months. Dust will be falling out of the air, and washed out of the air, for up to 2 years.

Now, you don't tell us the technology level of the people. You mention nomadic camps, but you also mention cities. Given all this, I think that a minimum amount of time for a medieval tech repopulation would be a year. For a near-industrial tech, six months. For a post-industrial tech, 2-3 months.

However...

One of the bigger problems you'll face (if you care about scientific realism) is that what's in the crater is not wonderful soil, a fertile loam ready for planting crops. While it depends on the geology surrounding the impact, the scientific reality is that the impact will expose bedrock and the ash/dush falling from the sky will be somewhat volcanic in nature. That's a fancy way of saying "crappy soil." It takes time for Mother Nature using wind, water, and biome-basic seeds to re-fertilize an area. This could take years and years. It could take decades. Heck, it could believably take centuries.

Add to this the question of water. If the impact occured over an aquifer, what you now have is big lake. If a river or lake was nearby, what you now have is a lake. If it's in a very rainy area, what you now have is a lake.

So, really... how long?

Which is why I'm advocating for the tag. It lets us handwave some of the uglier truths of Science. However, even with that tag, the time it takes for grass to grow, crops to grow, etc. (without which you can't graze animals) is at least one season.

So, 6-12 months depending on what season it was when the meteor hit.

This also heavily depends on the tech level of your civilization. medieval? 6-12 months. Pre- and post-industrial? Much less because food can be imported until crops grow. Could you import crops in a medieval era? Yes, it's just a bigger deal and therefore less believable.

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  • $\begingroup$ Out of curiosity, an impactor delivering enough energy to create a 15 km crater, how much heat would that transfer into the crust, how deep and how long would that take to dissipate to a .... habatable(?) degree? $\endgroup$
    – Gillgamesh
    Commented Mar 25 at 18:27
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    $\begingroup$ @Gillgamesh - not much time. I was fiddling with an impact calculator the other day, and the majority of the energy of the impactor is lost in the atmosphere as it breaks up before impact. We're still talking about an explosion in the hundreds of megatonnes, but the crater itself would be less than a kilometer deep, and would probably cool off to the point where people could check it out on foot in the space of a couple of weeks or less. The larger problem would be that everyone close enough to get there on foot would be injured or dead. $\endgroup$
    – jdunlop
    Commented Mar 25 at 18:47
  • $\begingroup$ @Gillgamesh Don't know and don't care. That's the point of shifting to the science-fiction tag. This Stack spends way, way, way, way, way too much time trying to make things "as real as possible." Every detail like that you add leads to AlexP's conclusion: you can't do this. $\endgroup$
    – JBH
    Commented Mar 25 at 20:00

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