2011 Christchurch Earthquake- Mike Ryan

Executive Summary- 200 words

On Tuesday February 22, 2011 10kms south-east of Christchurch’s central business district was struck by a devastating 6.3 magnitude earthquake. From the earthquake 181 people were killed and a further 7000+ were injured. Although this earthquake occurred more than five months after the September 2010 earthquake, it was still considered to be an aftershock of the earlier quake. The earthquake occurred due to a build-up of pressure between the Australian plate and the Pacific plate, the expulsion of this pressure was the cause of the quake. The result left the city in a tragic state, a huge economic and social mess that the country has still not been able to completely recover.

Due to minimal knowledge on how to predict earthquakes, New Zealand was struck by surprise and was not in a state of preparation for the event after just recovering from a higher magnitude quake several months earlier. This report outlines the tectonic movements that were responsible for the event, the human impacts, future predictions, technology used to monitor events and an overview of possible ways to minimise the disastrous effects of future events.

Tectonic Movements and Impacts- 600 Words

The Earth’s crust consists of a series of plates which are made of lithospheric materials. As the plates shift around liquid rock (magma) is expelled from the gaps in the plates, this then comes into contact with cold ocean water causing it to cool rapidly to form brand new lithospheric crust.1 Plate boundaries are either continental or oceanic based on the movement it creates at the plate boundaries. There are three main types of plate boundaries which are: convergent, divergent and transform.

Convergent Boundaries- Convergent boundaries consist of crust being destroyed as one plate is driven under another plate. These are known as Subduction zones, mountains and volcanoes are often found where plates converge due to one plate being forced upwards.2

Divergent Boundaries- Divergent boundaries consist of two or more plates pulling away from each other. As the two plates break away from each other the linear feature formed is called a rift. When the rift widens, it evolves into a rift valley. These often lead to the formation of volcanic islands.3

1 Dylan Prentiss, Characteristics of Plate Tectonics, Department of Geography, University of California, 20042 Lewis Thomas, Plate Tectonics, Pg. 5, 20133 John Carl Villanueva, Divergent Boundaries, 2009

Transform Boundaries- Transform boundaries are when two separate plates slide past each other in their movement. During this process of movement, lithosphere is neither created nor destroyed. Many of these transform boundaries are found on the seafloor. This slide of plates can often lead to major earthquakes.4

New Zealand is highly prone to earthquakes and volcanoes as it has two of the world’s major tectonic plates- the Pacific Plate and the Australian Plate. In the south of New Zealand, a major trench known as the Puysegur Trench5, formed through convergent plate movements forming a Subduction zone.6 The Australian plate subducts under the Pacific plate, down to approximately 200 kilometres. In the central south island of New Zealand, consisting of Christchurch, much of the plate movement and collision is taken up by the movement across the Alpine Fault. The movement across this fault is mainly transform boundaries as the plates shift together causing almost constant tremors through the centralised areas of New Zealand as well as convergent boundaries as the plates shift upwards causing some of the major volcanic activity throughout the area.

The 2011 Christchurch earthquake was caused by the pressure exerted between the Australian and Pacific Plates. The earthquake was “strike-slip event with oblique motion” mostly horizontal movement of the plates and some level of vertical movement.7 The earthquake had much greater vertical movement than horizontal movement. Convergent boundary movement was the leading cause of the earthquake, as major pressure was formed between through the Australian plate subducting under the Pacific plate, and then as the pressure was expelled, the earthquake was the result of this release.8 The earthquake struck at a shallow depth of 5kms and was measured at 6.3 on the Richter scale, this disaster affected the majority of the southern island and the base of the northern island of New Zealand9, showing the dramatic proportion of the damage that occurred.

4 Hobart King, Transform Plate Boundary, 20125 Kelvin Berryman, New Zealand: where two tectonic plates collide, GNS Science, 20126 National Geographic, Ocean Trench, 20137 New Zealand Herald, Christchurch earthquake, 24 February 20118 Wikipedia, Geology, 20139 Christchurch City Council, Christchurch Earthquake, 2011

Human Impacts of the Natural Disaster- 500 Words

“It is a very tragic situation and it’s a time of great agony”, stated Prime Minister John Key in response to the disaster. The February 2011 Christchurch Earthquake, had a substantial effect on the population throughout the whole of New Zealand. From the disaster there were 181 casualties from immediate and post disaster injuries/fatalities as well as 7,100+ injured.10 This disaster had a much greater proportion of damage in comparison to the September 2010 earthquake which struck with a greater magnitude. The damage left the country in NZ$16 billion in economic loss through destruction and damage. The disaster left areas of the country without access to power for up to 4 weeks with 95% of power restoration.

Short Term Damage-

Series of aftershocks, more than 11,200 aftershocks have been recorded by GNS Science since the earthquake.11

Road and bridge damage occurred and complicated rescue efforts12

City centre evacuation occurred Soil liquefaction and surface flooding occurred, this made rescue operations a lot harder,

and transportation of the injured to medical facilities was also difficult13

Of the 3000 buildings inspected within the central area of the city after the disaster, for safety precautions 45% of these were given red or yellow stickers to prevent access to these buildings14

Christchurch hospital experienced partial damage and was partly evacuated, however the lower portion of the hospital remained open for medical assistance15

Main Long Term Damage-

Major damage to highly important buildings such as the Christchurch Cathedral16 This held significant religious importance and was also a major identifying characteristic of the city itself17

10 Lori Peek, Social Impacts of the Christchurch Earthquake, Centre for disaster and risk analysis, 201111 Otago Daily Times, 11,000 aftershocks since Christchurch quake, September 201212 Radio New Zealand News, Fire Service Struggling to cope with Rescue Effort, February 201113 Radio New Zealand News, Main Roads to Christchurch open, February 201114 Radio New Zealand News, Painstaking work continues at devasted buildings, February 201115 Christchurch News, As it Happened:6.3 Earthquake rocks Christchurch, New Zealand16 New Zealand Herald, People likely to be trapped in Cathedral, February 201117 Allie Schreffler, Christchurch Earthquake leaves New Zealand in Despair, February 2011

Financial consequences, predictions from Prime Minister, John Key, predicted the disaster will cost the country more than $10 Billion and he expects the consequences to be long term18

Response to the event-

Teams from Australia, Japan, the United States, Britain, Singapore and Taiwan joined hundreds of local rescuers digging through the rubble in Christchurch in search of survivors19

The Red Cross immediately sent in teams to launch an emergency appeal to help the survivors of the earthquake20

Funds were sent in from many other countries, such as Australia, America and China Houses were demolished that were deemed unsafe and almost immediate reconstruction

began throughout New Zealand21

Future Predictions

Scientists state that the probability of extreme earthquakes occurring again in New Zealand, are highly likely. Since the major earthquakes of 2010 and 2011, the area of Canterbury has experienced almost 8000 aftershocks22, the majority of these have been of very low magnitude. Professor Jarg Pettinga stated that “Any number of those fault lines can rupture at any time when the stresses are built up”23 Based on the current rate of major earthquakes throughout New Zealand, it has been predicted that there is around 14% chance of a major, high magnitude earthquake occurring each year.24 New Zealand Scientists have stated that it is possible to predict some earthquakes of high magnitude through strong changes in the pattern of smaller ones over several years.25 They can also partly be predicted through scientists measuring and studying certain trenches, find out how often they erupt, and determine when they will next erupt as their history may indicate their future behaviour.26

Technology used to monitor and predict

There is no established way for seismologists so predict the date and time of an earthquake. They are able to use information from previous years to predict the generalised area, but it is very difficult to get the time and date of the event correct.

The only way scientists and seismologists have for determining when earthquakes will occur is through looking over the history of events and basing predictions off the commonality of earthquakes happening in certain areas. If there has been a steady flow of continuous earthquakes in an area,

18 Allie Schreffler, Christchurch Earthquake leaves New Zealand in Despair, February 201119 TerraDaily, World races to aid New Zealand quake rescue, February 201120 British Red Cross, Red Cross launches New Zealand Earthquake appeal, February 201121 Vernon Small, Commission dollars drained by Christchurch earthquakes, March 201122 Professor Jarg Pettinga, Predicting Future Quakes ‘not an exact science’ October 201123 Professor Jarg Pettinga, Predicting Future Quakes ‘not an exact science’ October 201124 Professor Jarg Pettinga, Predicting Future Quakes ‘not an exact science’ October 201125 Eileen McSaveney, Earthquakes-Living with earthquakes, The Encyclopaedia of New Zealand 2012-201326 Eileen McSaveney, Earthquakes-Living with earthquakes, The Encyclopaedia of New Zealand 2012-2013

this makes it a lot easier for predictions to occur. Areas where there is constant movement in plate technology at boundaries are also prone to experience a much greater number of events and along trench lines.

Another way predictions can be made is through the study of measuring land movements in areas that are being deformed using techniques such as Global Positioning System measurements and radar. Through this, determinations can be made on areas that are most likely for seismic activity to occur and if the likeliness is increased or decreased in these areas.27

Earthquakes however can be measured; this is done through the measurement of size: magnitude and intensity. Magnitude is a measure of the amount of energy released during the earthquake. This is measured through a seismograph and then recorded on the Richter scale; the measurement of the highest recorded seismic wave. A seismograph records seismic waves produced through the event. The intensity is an observation of the effects of the earthquake, this changes depending on how close an individual is to the epicentre; the core of the earthquake/centre.28

While there are no confirmed and reliable ways to predict earthquakes at this time seismologists recommend that people in earthquake prone areas to have a plan of what to do when a major one hits.

Dr Terry Webb of GNS science stated “We’ve got to plan around this- it’s something we shouldn’t be living in fear of”29

Possible Solutions

Due to how common earthquakes are through New Zealand, there have been several disaster plans implemented for all of the population to follow in times of emergency. The main disaster plan outlines: agreed roles and responsibilities for agencies participating in the response, it ensures that the national level response is co-ordinated, that the plan can be activated immediately and automatically and is as effective and efficient possible within the constraints of the event.30

For the most efficient levels of minimising the disastrous effects of these serious events in New Zealand, the disaster plan needs to be highly practised throughout the whole of New Zealand. This includes: programs in school to outline response to a serious situation, awareness days for the whole country to train the population on response to the situation if it occurs as well as the distribution of the Earthquake Initial Response Plan. The country needs to remain in a constant state of preparedness and expectation of another disastrous event happening in the near future, this will help prevent the

27 Eileen McSaveney, Earthquakes-Living with earthquakes, The Encyclopaedia of New Zealand 2012-201328 Bill Haneberg, How do scientists measure earthquakes, January 200829 Terry Webb, GNS Science, 201330 New Zealand Government, Wellington Earthquake National Initial Response Plan, April 2010

number of casualties and train people to act in a smart way that will reduce city damage, violence and people acting in an improper way.

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