The Gloucester forward was sent off for striking an opponent during his team's Amlin Challenge Cup victory over Mont-de-Marsan in France earlier this month.
Hazell's case was heard by independent judicial officer Roger Morris in Dublin. He pleaded guilty to striking Sebastien Ormaechea and cannot play again until January 21.
The player gave evidence and made submissions to Morris, together with Gloucester rugby director Nigel Davies and ERC disciplinary officer Roger O'Connor.
Immediately after the game, which Gloucester won 11-6, Davies suggested that Hazell had reacted to extreme provocation from a Mont-de-Marsan player or players.
The Aviva Premiership club provided photographic evidence of marks around Hazell's eyes, but no citing complaints were subsequently made to ERC by match commissioner John West, who could not find sufficient video evidence of foul play.
In a statement, ERC said: "The judicial officer (Morris) determined that Hazell had intentionally struck Ormaechea with both the fist and the knee.
"Having also determined that any suspensions he would impose for the offences would run concurrently, and as striking with the knee carries greater penalties than striking with the fist under the IRB recommended sanctions for offences committed within the playing enclosure, the judicial officer decided on a top-end entry point of 16 weeks.
"Taking into account aggravating factors, he added a further two weeks given Hazell's disciplinary record and his failure to uphold the image of the game.
"Then following consideration of Hazell's guilty plea and his exemplary conduct during the hearing, the judicial officer deducted four weeks before imposing a suspension of 14 weeks. Hazell will be free to play on Monday, 21 January 2013. Both ERC and the player have the right to appeal the decision."
- Sports & Recreation