Prime Minister John Key has announced a Royal Commission investigating the reasons for the devastation wreaked by the Christchurch earthquake.

The inquiry, headed by High Court judge Mark Cooper, would focus on why the CTV and PGG buildings collapsed in the 6.3 magnitude quake on February 22, killing dozens who were inside, Mr Key said.

It would consider whether the building standards and codes in place at the time of the earthquake were adequate, he said.

"So many lives have been lost as a result of the February 22 earthquake that we must find answers, particularly about why such a significant loss of life occurred in two buildings," Mr Key says.

"We are determined to get those answers, and I believe that this Royal Commission, along with the technical investigation by DBH, will do that."

The Grand Chancellor Hotel, which is condemned due to earthquake damage, and the devastated Forsyth Barr building will also be investigated by the Commission.

It will consider whether design of the devastated buildings and whether they were compliant with building regulations at the time of their design.

Mr Key said the Commission was a key step in rebuilding Christchurch.

He ordered it to release an interim report to the Government in six months and a full report within a year.

"This independent investigation is a vital step in rebuilding public confidence in the future of the Christchurch CBD," he said.

"It is important that the reasons for the severity of the damage to certain buildings and consequent loss of life are understood as soon as possible."

Mr Key commended Justice Cooper for his experience in the Resource Management Act and local government.

Two other Commissioners are yet to be also be appointed. Terms of reference of the Commission are to be finalised in consultation with Justice Cooper.

Attorney-General Chris Finlayson will have administrative responsibility for this inquiry, as with the Royal Commission into Pike River.

Six more victims named

Meanwhile, police have released the names of six more victims of the Christchurch earthquake.

The release takes the total of number of names released to 123, while the death toll from the earthquake stays at 166.

Those named today are:

* Lalaine Collado Agatep, 38, from the Philippines.

* Carey Stuart Bird, 48, a New Zealander who had been living in Australia.

* Miki Hayasaka, 37, from Japan.

* Yuko Hirabayashi, 28, from Japan.

* Hifumi Hoshiba, 41, from Japan.

* Kyle Brandon Jack-Midgley, 27, from Christchurch.

Miki Hayasaka was a nurse studying at the Canterbury TV building in the Christchurch city centre.

She updated her Facebook profile with the message "look up at the blue sky, look around me always, look at myself and look toward my future of happiness" at 9:18am on February 22.

Hours later she was counted among the missing in the wake of the devastating earthquake.

Her friend Isaac Savage said Ms Hayasaka was an outgoing woman who was a teenager at heart and had many friends.

He said she loved New Zealand's environment and laid-back lifestyle.
"She hung out with young people, she was the life of the party."

Kyle Jack-Midgley was also in the Canterbury TV building demolished by the February 22 quake.

Ryan Jack-Midgley posted on his Facebook page during the week of the earthquake: "Kyle, I'm coming to find you and I expect you to be the first one to tell me off for crying when I do ... wish me luck people."

But on February 25, hope was mingled with frustration when Ryan posted:

"Without at all eliminating hope, today was a bad day. We were told that there is still a chance survivors could be found in the CTV building and as we know, if anyone was gonna be that survivor he'd be my brother.

- with Newstalk ZB