知る:know of, to have simple information, e.g, it exists or not.
わかる: know, understand.
「知らない人」- a stranger, a person you don't know of.
「よく分からないひと」 - a strange person, a person you cannot understand well.
「私の父はオマーンという国を知りませんでした」
My father didn't know of Oman.
(He didn't even know that the country named Oman exists)
「彼はオマーンのことを、わかっていない」
He doesn't understand Oman. / He doesn't know Oman well.
(He knows of the very existence of a country named Oman but he still doesn't understand well people, culture and other contents about Oman).
「彼は有名人だと、知りました」
I heard that he is a famous person.
(You cannot tell your reasons because it is only that you heard it).
「彼は有名人だと、わかりました」
I found that he is a famous person.
Considering lots of information, you concluded that he was a famous person.
(You can tell your reasons why)