Download Christchurch Earthquake Assessment by Mike Ryan

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.
1

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
Dylan Prentiss, Characteristics of Plate Tectonics, Department of Geography, University of California, 2004
Lewis Thomas, Plate Tectonics, Pg. 5, 2013
3
John Carl Villanueva, Divergent Boundaries, 2009
2

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, 2012
Kelvin Berryman, New Zealand: where two tectonic plates collide, GNS Science, 2012
6
National Geographic, Ocean Trench, 2013
7
New Zealand Herald, Christchurch earthquake, 24 February 2011
8
Wikipedia, Geology, 2013
9
Christchurch City Council, Christchurch Earthquake, 2011
5
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

10
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
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
Lori Peek, Social Impacts of the Christchurch Earthquake, Centre for disaster and risk analysis, 2011
Otago Daily Times, 11,000 aftershocks since Christchurch quake, September 2012
12
Radio New Zealand News, Fire Service Struggling to cope with Rescue Effort, February 2011
13
Radio New Zealand News, Main Roads to Christchurch open, February 2011
14
Radio New Zealand News, Painstaking work continues at devasted buildings, February 2011
15
Christchurch News, As it Happened:6.3 Earthquake rocks Christchurch, New Zealand
16
New Zealand Herald, People likely to be trapped in Cathedral, February 2011
17
Allie Schreffler, Christchurch Earthquake leaves New Zealand in Despair, February 2011
11
Response to the event
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

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,
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.
18
Allie Schreffler, Christchurch Earthquake leaves New Zealand in Despair, February 2011
TerraDaily, World races to aid New Zealand quake rescue, February 2011
20
British Red Cross, Red Cross launches New Zealand Earthquake appeal, February 2011
21
Vernon Small, Commission dollars drained by Christchurch earthquakes, March 2011
22
Professor Jarg Pettinga, Predicting Future Quakes ‘not an exact science’ October 2011
23
Professor Jarg Pettinga, Predicting Future Quakes ‘not an exact science’ October 2011
24
Professor Jarg Pettinga, Predicting Future Quakes ‘not an exact science’ October 2011
25
Eileen McSaveney, Earthquakes-Living with earthquakes, The Encyclopaedia of New Zealand 2012-2013
26
Eileen McSaveney, Earthquakes-Living with earthquakes, The Encyclopaedia of New Zealand 2012-2013
19
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
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.
27
Eileen McSaveney, Earthquakes-Living with earthquakes, The Encyclopaedia of New Zealand 2012-2013
Bill Haneberg, How do scientists measure earthquakes, January 2008
29
Terry Webb, GNS Science, 2013
30
New Zealand Government, Wellington Earthquake National Initial Response Plan, April 2010
28
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