Lelioara,
BLAME or FAULT?
Oxford Dictionary of English (2006)
BLAME: verb: (with object) feel or declare that someone or something is responsible for a fault or wrong. The inquiry blamed the train driver for the accident.
n (blame something on) assign the responsibility for a bad or unfortunate situation or phenomenon to someone or something. They blame youth crime on unemployment.
noun: [mass noun] responsibility for a fault or wrong. His players had to take the blame for the defeat. They are trying to put the blame on us.
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FAULT: verb: (with object) [usually with negative] criticise for inadequacy or mistakes: her superiors could not fault her dedication to the job. | You cannot fault him for the professionalism of his approach.
noun 1. An unattractive or unsatisfactory feature, especially in a piece of work or in a person�s character. My worst fault is impatience.
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2. [mass noun] responsibility for an accident or misfortune. If books were not selling, it wasn�t the fault of the publishers. | It was his fault she had died.
In my opinion, although these two words are very similar, I would not describe them as synonyms, because one cannot automatically replace the other, (as Foose1 and Apodo make clear). Moreover, they are used in slightly different ways.
The word, �blame�, is frequently used as a verb: �I blame you for this error� is Standard English.
However, �fault� is virtually never used, in a positive sense, as a verb. �I fault you for this error� is NOT Standard English.
(�I find fault with you for this error� is Standard English, but here �find� is the verb and �fault� is used as a noun.)
The word, �blame�, is frequently used as a noun, in the sense of �responsibility�; �culpability�; �fault�; �guilt�; �accountability�, etc. �I am sorry! You must accept the blame for this error�.
The word, �fault�, is also frequently used as a noun, in the sense of �responsibility�; �culpability�; �blame�; �guilt�; �accountability�, etc. �I am sorry! The fault for this error is yours�.
It is when the two words are used as nouns that they are most similar and appear to be synonymous.
There are several other dictionary references to these two words, but I think that they confuse the discussion. I have dealt only with the references that I think that you want high-lighted.
I hope that I have been able to help you.
Les