I chose to do my case study on the 2011 Christchurch earthquake in New Zealand. I chose it because I have always been interested in Liquefaction and the damage that is causes to infrastructure. The boundary between the subducting oceanic plate and the Australian plate runs right through the middle of New Zealand. New Zealand is part of the Ring of Fire. The area is highly tectonically active so New Zealand receives a lot of earthquakes. The Christchurch earthquake occurred at 12:51 PM New Zealand time on February 22, 2011. The focus of the earthquake was very close to the surface and it had a magnitude of 6.3. The earthquake was powerful enough to generate its own aftershocks, even though it was technically an aftershock a larger but less destructive earthquake six months previously. The earthquake was caused by a previously unknown fault line that was 6 km from the center of Christchurch. The type of faulting that caused the earthquake is called reverse faulting. The secondary hazard besides the actual earthquake itself is the liquefaction that occurred as a result of the earthquake. The liquefaction destabilize the foundations of the buildings and caused them to partially sink into the ground or collapse. The liquefaction deposited thousands of tons of silty sand all over Christchurch. The liquefaction actually caused more damage than the shaking from the earthquake. 185 people died in the earthquake and 7000 people were injured.
Over the years New Zealand has taken many steps to mitigate the damage caused by earthquakes. They have retrofitted their bridges, and lifelines to hopefully withstand earthquakes. They also practice earthquake drills in schools and teach the children the safest places to be during an earthquake. The problem I caused the most damage was the development of residential neighborhoods in areas that they knew had a high risk of liquefaction. When the earthquake occurred most of the houses in these areas were destroyed from a combination of the liquefaction and the shaking from the earthquake.
Christchurch is still rebuilding from the earthquake and may have completed about half of the Christchurch central recovery plan. It focuses on a few key projects that will help revitalize Christchurch. Christchurch central business district was mostly destroyed so during the rebuilding process they have changed the Central business district hopefully for the better. The government has also bought out the houses in the areas with high liquefaction and there are plans to turn the area into a park.
Christchurch was not caught completely unawares by the liquefaction that occurred during the 2011 earthquake. The earthquake that had occurred in September of the previous year had minor liquefaction and scientists knew that liquefaction was possible in the area. Christchurch was prepared to handle an earthquake but they were not prepared for liquefaction.
Since the Christchurch earthquake, New Zealand’s economy has been bolstered by a booming construction economy. Other earthquakes have hit Christchurch in the last five years and they seem to be slowly rebuilding.