Troops will relieve police officers on Monday morning on the cordon in the central business district of Christchurch, which was hit hard by the earthquake.
Colonel Roger McElwain says the police have been running on adrenaline since the magnitude 7.1 earthquake at 4.35am on Saturday, but are now getting tired.
Two contingents of 80 soldiers are due to begin 12 hour rotations to maintain the road blocks from 8am.
Colonel McElwain says 80 police reinforcements brought in from Auckland on Saturday, will be replaced later on Monday with officers from Wellington and Timaru.
Police Superintendent Dave Cliff told Morning Report on Monday that several known criminals had tried to drive into the city posing as council staff, but were stopped and will be dealt with by the court.
Three Defence teams will also start testing water quality in the region for the Canterbury District Health Board.
Fire crews from around the country are arriving in Christchurch to give fatigued personnel there a rest.
The Fire Service says Dunedin and Invercargill crews arrived on Sunday to start working in the city centre.
Management crews have also arrived from Dunedin and Auckland.