Earthquake in Christchurch

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The scale of the astounding and tragic events in Japan on March 11, 2011 very quickly eclipsed news of the February 22 earthquake in New Zealand. Since my wife and I were on holiday in Christchurch at time the latter will always remain a deeply disturbing personal experience.

We were very fortunate to be able to escape from the wreckage of our hotel with no more than a few minor cuts and bruises, but lost all our belongings, our valuables and our hired car. We were evacuated in borrowed clothes by the New Zealand RAF two days later. Others nearby were not so lucky; more than 180 people lost their lives and very many more were injured.

As a surveyor I cannot help but dwell on the enormity of the problems which Christchurch must address and note how the machinery of survival and recovery has swung into action.

The widespread destruction of the Central Business District where 215 buildings currently face demolition has been widely reported, but Christchurch and its surrounds suffered enormous and lasting damage to its services, utilities and communications. Ground movements and the effects of subsurface and rising liquefaction affected 2,000 km of roads and opened 38,000 significant cracks. Water supply and sewerage pipes that were extensively fractured silted up and will be hard to replace where deep voids have appeared in the underlying ground. One hundred and fifty emergency crews have been mobilized to deal with water and waste pipe damage giving priority to locations where other infrastructure is affected and where waste is overflowing into neighboring properties and waterways. The New Zealand military set up a mobile water treatment system to produce 10,000 gallons of clean drinking water per day from seawater, and fresh water was brought in from elsewhere by tankers. During the immediate aftermath of the earthquake bottled drinking water was brought back by the aircraft returning from evacuation flights. Two thousand portable toilets were positioned on public footpaths and by the end of March, 27,000 chemical toilets had been delivered to the city’s worst hit eastern suburbs with another 14,000 on the way. Electricity supplies were seriously affected, four 66kv power lines were seriously damaged, and the entire network is still in a fragile state.

Emphasis has been given in press reports to the damage to businesses, computer systems, commercial properties, and historical buildings. Five thousand cars had been trapped and many destroyed. It is less well recorded that 10,000 homes may have to be demolished, all brick chimneys are to be taken down if they haven’t already collapsed, and 1,000 heaters per week were being supplied as the south island winter was coming. Businesses that appear to be prospering are the demolition companies who are actively removing millions of tons of rubble to disposal sites outside the city.

While recovery efforts are being made there is the everyday reality of aftershocks and the fear of another major earthquake, every one posing danger and the risk of further damage. Christchurch was hit by an earthquake of 7.1 on the Richter Scale in September 2010 and this one, at 12:51 p.m. on February 22 was regarded as a consequential but major and more damaging aftershock measuring 6.343, which finished structures already damaged and vulnerable. Fifteen minutes later there was another measuring 5.8, and less than two hours later another at 5.9. The people of the Canterbury area have to live with the stress and worry of aftershocks which are likely to continue for a year or more. By early April more than 1,000 had been felt with two or three measuring between 4.0 and 4.9 per week. Power was disrupted once again on April 15th by a strong aftershock of 5.3.

Disturbance of the ground has considerable implications for the New Zealand cadastre which operates a system of fixed and carefully measured boundaries. The preservation of equity in properties is a major concern. Fault lines and liquefaction have disturbed many control stations, boundaries have changed, buildings have moved onto adjacent land and some land has been lost in rivers. The full impact on properties will probably not be known for decades. One of the first actions of Land Information New Zealand (LINZ) was to release aerial photographic coverage of the Christchurch area taken on February 24. This photography can be viewed at Map revision will be required for the rebuilding of roads and the sewerage systems and an airborne laser profiling system will establish how far ground levels have changed. Ground compaction from shaking has taken place and some areas are now more prone to flooding. There is also a fear that flood banks have been weakened and ongoing monitoring will be required.

The earthquakes in the Canterbury area have highlighted the fact that insufficient information was known about the subsurface structure. Highly sensitive gravity meters are now being used to determine changes in deep geology. A geophysical team combining the resources of Canterbury University and the Canadian University of Calgary are using seismic recording equipment to investigate deep seated faulting in the zones of movement. Another team from Canterbury University’s Civil Engineering Department under Professor Stefano Pampanin is using a high precision 3-D Riegl Z420 laser scanner to detect if buildings are leaning and to make recommendations regarding demolition.

The destruction has triggered much activity for surveyors and engineers but reconstruction is already in mind. The instability of the area is likely to result in a city with a different appearance. Much of it sits on soft ground, the water table is not far down and soil tests will be required to establish the strength and bearing capacity needed before redevelopment can proceed. There are likely to be fewer high rise buildings, more open spaces and more trees. On a serious but slightly lighter note, a matter which may be of current concern to some surveyors and engineers was the damage sustained by the Christchurch Brewery. Production has ceased and beer was rationed, although some vital kegs of Guinness were rescued in time for St.Patrick’s Day.

Apart from the drama of our escape, my overwhelming memory will be the tremendous concern and kindness shown to us by the Christchurch people, particularly the owner of our hotel, Mr. Antony Gough, and the emergency services provided by the Red Cross, the Salvation Army, Victim Support, college students, volunteers from many other organisations and the New Zealand RAF. I should like to mention that the Christchurch Earthquake Appeal is still in great need of funds to help those who have suffered and who will continue to suffer for a long time to come.

Author Note and Update: As of late July 2011, life has become no easier for the people and the businesses in Christchurch. The February 6.3 earthquake which I experienced has been classified as an aftershock of the 7.1 magnitude quake that caused much less damage in September 2010. Christchurch no longer hits international headlines but since that first event there have been about 7,500 aftershocks, 30 of them of magnitude 5.0 or higher causing more damage, the latest being 5.1 on July 22 affecting a wide area of the Canterbury Plains.

Since February, 360 buildings have been demolished or made safe in the center of the city, a figure which is expected to rise to around 900. Huge efforts are being made to repair and reinstate damaged infrastructure, but ongoing shocks are shaking the confidence of local people and most insurers have put a freeze on new policies, thus further diminishing hopes of early recovery. While New Ze
aland suffered much less than Japan, the financial consequence has been proportionately higher. The estimated cost of $20 billion approaches 10% of the country’s GDP compared to the figure of 1% in Japan.

Malcolm Anderson served with the Ministry of Land and Survey, Northern Nigeria from 1957-1977, and was Chief Land Surveyor for the Milton Keynes Development Corporation (UK) from 1977­1992. He is now retired. A version of this article appeared in the May/June issue of Geomatics World.

A 1.243Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE