The traffic signal fault in Christchurch which caused significant delays this morning in the CBD has now been fixed.
Originally thought to have been caused by this morning's earthquake, the actual cause of the fault is still not known.
It began around 10 last night.
Christchurch Transport Operations Centre says congestion is now expected to ease.
It says the signals team is working with the Christchurch City Council's IT department to find an exact cause.
Earlier this morning the strong quake woke up most of Christchurch.
GNS says it measured 4.3 magnitude just after 3.30am this morning.
It was of strong intensity and was close to the central city - just five kilometres south of Christchurch.
It also was just five kilometres deep and has been followed by several aftershocks.
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Rattled residents of Christchurch have reacted on social media to the shake.
Roana Noah wrote on Facebook: "Happy leap day everybody, apparently that meant leap out of ya bed to save yourself from an earthquake..."
Euan Mason said: "Wheeee. That one woke me. Mag 4.3, but only 5 km deep and quite close (in Cashmere)..."
Meanwhile, Claire from New Brighton, east of the central city, thought the quake felt like it was bigger than a 4.3.
She told Newstalk ZB's Bruce Russell that she had to hang on to the kitchen bench.
Victoria Rutherford reported hearing booming noises like a canon, and Mike Yardley called the quake a heart thumper.
READ MORE: Deadly 2011 quake: Before and after pics
Yardley wrote on Facebook: "Thump...nasty shake in south Christchurch. 4.3 mag. Centred in cashmere. Only 5km deep! Yuck..."
Margaret Agnew also wished everyone a happy leap year - literally - and tweeted she hadn't done the down the hall dash to the kids in the night since ages ago.
Many more complained about it being a lousy start to the week.
There have been no reports of damage.
Police said there were no reports of damage and no increased calls to emergency services.
As the quake measured under magnitude 5 there was no need to check buildings.
But the police spokeswoman said this might at change after sunrise when property could be properly surveyed.
Newstalk ZB reporter Scarlett Cvitanovich told early morning host Rachel Smalley that the quake hit right next to Cashmere High School.
She says a lot of people around the Sydenham, Cashmere, St Martins areas when they reported it felt like it was right under their houses, it actually was.
Ms Cvitanovich says it's been a while since people in Christchurch have been woken up by something so loud and violent.
She says it brings back memories of the September 2010 earthquake.
A spokesman from the Christchurch Transport Operations Centre (CTOC) said following the quake, a fault is affecting traffic signals in the central city this morning.
"They are on and turning green, yellow and red however this fault means the traffic lights in the central city are now all working independently from each other and are no longer working together to optimise flow through the CBD."
He said this has the potential to cause significant delays in and around the central city for the morning peak traffic period.
"Motorists are advised to leave early and allow for delays this morning. Traffic signal engineers are working on the issue."
Gay from St Martins, which is close to Cashmere, told Newstalk ZB that she had just fed the cat when the earthquake hit her this morning.
"It was so noisy, it was vicious. Everything rattled and it was disgusting."
She said she wants the quakes to go away as Christchurch residents are over it.
A lady named Julie said it felt worse than the Valentines Day shake.
"This is the loudest one that I've ever heard."
Shirley, who lives in Cashmere, also said her house just "shook like anything".
"I was dead asleep and the next minute the whole place just violently shook and the next minute my dog started yelping."
-additional reporting Newstalk ZB