Dr Neil Thomas, an expert in natural hazards and disaster management.
Dr Thomas, who is based in Kingston University’s School of Earth Sciences and Geography, discusses in the Q&A below issues such as the work of the search and rescue teams and the challenges of rebuilding and making Christchurch safe.
What needs to be done now to safeguard people and buildings? What are the main challenges ahead?
Today (Thursday 24th February) there are some 320 specialist search and rescue workers on the ground in Christchurch to carry on the search and rescue work. Their main priority will be to continue searching for survivors as long as there is hope of successful rescue. Other work will be to inspect and ensure that lightly damaged buildings are safe for reoccupation and to make more seriously damaged buildings safe from further, or total, collapse. Naturally, there will be a massive clear-up operation which will last for several weeks.
In human terms, the welfare centres are giving temporary shelter and bedding to people but others have left the area to visit friends or relatives in other parts of South island, away from the aftershock zone. The city of Dunedin, 300km to the southwest, has made accommodation available to temporary evacuees from Christchurch. The Christchurch emergency management group has confirmed that food and fuel supplies are reaching the affected area and local supermarkets are reopening. Water is a problem, with losses during the quake and the possibility of supply contamination meaning that people are being advised to use water sensibly.
There are always dangers and challenges for rescue workers in earthquake affected areas. There is the threat posed by more aftershocks which can destabilise already damaged buildings and critical infrastructure and put rescue workers at risk. There are challenges associated with the clear-up operation and, of course, the issues of raising the population’s morale and the more long-term problems of dealing with bereavement and loss of livelihood. New Zealanders are resilient people but a disaster like this can severely test that resilience. Our thoughts are with them all and, as an international community, we should be prepared to help in any way we can.
Will there be aftershocks and how likely is it that Christchurch will experience another quake of this magnitude?
There have already been many aftershocks that hampered the initial search and rescue operations. These aftershocks are likely to decrease in magnitude and frequency throughout today (February 24th) and Friday but we can’t be certain that this will happen. We can’t forecast when the next event of this magnitude will occur in the area.
How long could it take to make safe and rebuild Christchurch?
Over the next week or so, as more details emerge, the search and rescue teams will become more aware of the extent of devastation but it’s possible that the clear-up operation could take many months. A big problem with the built environment is that the central business district has been very badly affected which could have a major knock-on effect for the region’s commercial operation in the coming months.
Why has this quake been so devastating when last September’s was of a higher magnitude?
The depth of the September 2010 event was approximately twice that of the February 2011 event, though both were very shallow and therefore potentially devastating. The epicentre location is also a factor – generally, areas further from the epicentre tend to be less affected than those closer. The February 2011 earthquake happened 10km south east of Christchurch while the September 2010 event had an epicentre 45km west of the city. The time the quake hits is important too – the September 2010 event stuck at 4:35 am local time when most people were asleep at home, rather than at work. The February 2011 event struck at 1:52pm, just around lunchtime on a working day when commercial buildings were occupied in the central business district. The epicentre of this event was closer to the central business district which made the commercial infrastructure more vulnerable. The combination of all these factors probably contributed to the more devastating effects, particularly in terms of fatalities, this time around.
Why did there appear to be no warning?
Unfortunately, most major earthquakes do not give prior warning which is why rapid onset events like this often take people by surprise. This event was, according to the United States Geological Survey, the largest of an aftershock sequence following the September 2010 event.