Astwood was found with a set of keys and security access cards - but police withdrew a charge that he had stolen them.
He appeared from custody at a Christchurch District Court hearing at Rangiora courthouse today after earlier admitting charges of burglary and breaching the cordon.
He was also sentenced for breach of community work and release conditions, as well as a theft and two of causing intentional damage. Judge Jane Farish told him: "You put your own life in danger when you entered into the red zone and entered the Hotel Grand Chancellor. It was destructive behaviour and it put other people in danger too, if anything happened to you while inside.
"Your purpose in entering the building was not to cause damage but you decided to drink as much alcohol as you could find, and you did so. When found by police you were incredibly intoxicated."
Defence counsel Vicki Walsh said: "His offending is triggered by alcohol abuse," which Judge Farish accepted and added: "He's probably got a genetic pre-disposition."
Ms Walsh said her client had been in the city centre when the February 22 earthquake rocked the city.
On October 4, he got drunk and was "drawn back" to the city centre, and entered the Grand Chancellor to "see what was behind" the damaged facade.