The house where the explosion occurred - 9 Marble Court in the suburb of Northwood - was completely destroyed on July 19.
Nine homes were damaged when the sudden blast obliterated the house, sending chunks of roof tiles and other debris over the neighbourhood.
One man was rushed to Christchurch Hospital where he was placed on life support. Five others were also taken to hospital.
Neighbours and passers-by pulled stunned survivors from the burning debris and were amazed that no one was instantly killed.
Charges have now been filed under the Gas Act 1992 against two defendants.
It follows an investigation led by Energy Safety of Worksafe New Zealand, in consultation with police, Fire and Emergency New Zealand and the Crown Solicitor’s office.
The first appearance will be on August 18 this year at the Christchurch District Court.
WorkSafe said today it was unable to provide any further information on the case.
However following the incident, it was revealed a contractor had worked on the house which had gas issues just one day before it exploded.
WorkSafe was working to determine "the immediate and underlying causes" of the event.
It said it had made efforts to contact all of the people affected by the incident, but is asking anyone involved who has not been in touch with it to email marble.court@worksafe.govt.nz.
Kevin Smith, who was crushed in the debris and put in an induced coma for a month, spent about eight weeks in hospital. His wife Annette was also hurt.
The Greymouth man and his wife were staying at his friends' Marble Court home when the explosion happened.
Paddy Blanchfield, Smith's son-in-law told the Herald on Sunday late last year they had been "battling" away with their injuries.
Smith suffered severe upper body burns and needs skin grafts.
"That's how bad he was. He has had a lot of skin grafts going on. Kevin was burnt in his lungs, his arms and his face- his whole upper body. Annette has had superficial wounds that didn't require skin grafts and has healed up pretty well physically. They are both traumatised." Blanchfield said.
"They will never be the same again. This explosion has shortened their lives, they are all psychologically affected by what's happened."
Fire and Emergency NZ area commander Dave Stackhouse told the Herald at the time of the explosion that all of Northwood was connected to piped gas, but it was not immediately clear how there had been a leak.
