What is the difference between 仮定 and 想定?


I see a lot of different explanations online but I'm not sure if I understand
the nuances correctly

From what I can gather:

仮定 is used when a situation is unclear and an assumption is made based on
facts and logic

想定 is used when imagining a possible situation and assuming it happened

Considering this, I have trouble telling the difference between these
sentences for example:

>   1. 今，大地震が起きたと **仮定** したらまずどうしますか
>
>   2. 今，大地震が起きたと **想定** したらまずどうしますか
>
>

I would like a more detailed explanation and if possible, some examples that
show where one would be used and not the other.




仮定 is close to "hypothesis", and it is can be used with something unlikely or
even impossible. 想定 is close to "anticipation", "expectation" or sometimes
"assumption". It is usually used when you vividly imagine or anticipate
something, or when you do a serious planning/drill/training on the assumption
of something.

> 今、大地震が起きたと仮定したらまずどうしますか。  
>  [?] 今、大地震が起きたと想定したらまずどうしますか。

This use of 想定 sounds odd to me because this is merely a hypothetical
question, i.e., the speaker knows an earthquake is unlikely to happen _today_.
You usually have to use 仮定 instead.

> 大地震が起きたと想定して、今から避難訓練を行います。  
>  大地震が起きたと仮定して、今から避難訓練を行います。

Both are okay, but 想定 sounds the quake is more likely.

> この地域で大地震が起きると10万名以上の死者が想定される。

You cannot use 仮定 here because the number of deaths is expected/anticipated,
not hypothesized.

> 想定質問 anticipated/expected/potential question (i.e., likely to be asked in an
> upcoming presentation)
>
> 仮定の質問 hypothetical question (e.g., "what if you were a president of the
> US?")
>
> この状況は想定できなかった。 The situation was beyond my expectation/imagination.
>
> この状況は仮定できなかった。 (does not make sense)




仮定 is close to "hypothesis", and it is can be used with something unlikely or
even impossible. 想定 is close to "anticipation", "expectation" or sometimes
"assumption". It is usually used when you vividly imagine or anticipate
something, or when you do a serious planning/drill/training on the assumption
of something.

> 今、大地震が起きたと仮定したらまずどうしますか。  
>  [?] 今、大地震が起きたと想定したらまずどうしますか。

This use of 想定 sounds odd to me because this is merely a hypothetical
question, i.e., the speaker knows an earthquake is unlikely to happen _today_.
You usually have to use 仮定 instead.

> 大地震が起きたと想定して、今から避難訓練を行います。  
>  大地震が起きたと仮定して、今から避難訓練を行います。

Both are okay, but 想定 sounds the quake is more likely.

> この地域で大地震が起きると10万名以上の死者が想定される。

You cannot use 仮定 here because the number of deaths is expected/anticipated,
not hypothesized.

> 想定質問 anticipated/expected/potential question (i.e., likely to be asked in an
> upcoming presentation)
>
> 仮定の質問 hypothetical question (e.g., "what if you were a president of the
> US?")
>
> この状況は想定できなかった。 The situation was beyond my expectation/imagination.
>
> この状況は仮定できなかった。 (does not make sense)

