christchurch earthquake Flashcards
what is some background info on christchurch?
-advanced economy with internation clout: member of of OECD
-population size: 340,000
-high gdp $39,000 (48th in the world)
-88% of the population use the internet
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what is the tectonic setting of new zealand?
-a hinge found along the boundary between the north and south
-subduction occurs to the east of the north island and the west of the south island
-conservative boundary in the south island
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what caused the christchurch earthquakes?
caused by movement along smaller faults such as the greendale fault
what is plate boundary unzipping?
a theory that may help predict where earthquakes may occur in the future. the geogolical evidence suggests that movement on a plate boundary in one location can disperse the energy along the boundary
what is seismic lensing?
occurs when seismic waves radiate out from the epicentre and rebound off rocks such as basalt and granite.he Port Hills to the south of the February epicentre are mostly composed of Basalt, and the waves reflected off the hard rock and reverberated back towards Christchurch, causing the city to experience further shaking.
what is the geology like at christchurch?
The large Canterbury Plain on which Christchurch sits is made up mostly of alluvial deposits (sediment deposited as rivers flood over the flood plain). This makes the area more susceptible to liquefaction, as it is unconsolidated material (9m of liquefiable material underneath Christchurch).
info on the Darfield earthquake (4th september 2010)
Magnitude 7.1
40km West of Christchurch
Depth: 10km
24km surface tear (Greendale fault)
No fatalities
Some land move 4m sideways in less than one second
Impact measured in economic damage to buildings and infrastructure
info on christchurch (Lyttelton) earthquake (22nd febuary 2011)
Magnitude 6.3 (classed as an aftershock of the Darfield quake)
10km SE of the CBD of Christchurch
Depth: 5km
15km surface rupture
Ground movement: Fastest ever ground acceleration in New Zealand (4x faster than the acceleration rate of the mag. 9.0 earthquake in Japan 2011)
Less powerful, but more destructive than the Darfield earthquake
Over 300 aftershocks
what were the social impacts of the earthquakes?
185 deaths (115 of these were from the collapse of the CTV building)
7,000+ injuries
Population loss
20,000 people had left the city by 2012 (of 380,000 population) = 5.3%
Population only returned to pre earthquake levels in 2017
Out-migration of skilled workers (e.g. Doctors)
Others could not leave for economic reasons (can’t sell houses)
Psychological trauma (especially kids): depression, divorce, domestic violence
Homes without working toilets for weeks, sometimes months
Homelessness (insurance claims were still being debated seven years after the quake leaving thousands in limbo whilst waiting for decisions on whether their houses could be rebuilt, or if they could claim to be re-housed). “an area more than four times the size of London’s Hyde Park was deemed uninhabitable” The Guardian 2014
Temporary closure of schools (due to liquefaction affecting sewage and water pipes, not damaged buildings): 84% back in school within 3 weeks
Positive community spirit (Farmy Army)
what were the economic impacts of the earthquakes
Cost to NZ: $40 bn for redesigning and rebuilding (20% of 2011 GDP) - impact on national economy short-lived
Estimated cost of repairs to reach £8 billion. Interest rate cut to deal with the damage leading to a fall in the value of the NZ dollar.
Damage to city: Christchurch Cathedral (also a historic site), roads, schools…
100,000 buildings demolished or severely damaged (half of the city’s buildings)
CTV and PGC buildings collapsed
26 storey hotel grand chancellor was displaced by half a metre and had to be demolished
80% of Sewage and water systems were destroyed
Reduced property prices and skyrocketing rental prices
Long wait for insurance pay-outs
Rising unemployment (initially)
Boom in construction industry and, later, tourism
Region’s economy grew 31% in the following 5 years, creating 50,000 new jobs
The cost of building a new home in Canterbury (excluding land) rose 52 percent in the eight years to September 2017 (This compares with 40 percent nationally).
Rugby world cup matches scheduled to take place at Lancaster Park had to be moved to other venues
what were the physical/environmental impacts of the earthquakes?
SE suburbs experienced 50cm of ground uplift
City centre subsidence caused by liquefaction
Deformation of the surface due to crustal fracturing
Liquefaction caused 200,000 tonnes of saturated silt to well up to the surface where it flowed as streams.
Slope failure, rockfalls and landslides in the steeply sloped, volcanic Port Hills area
what was the preperation and monitering like for the earthquakes?
New Zealand has had strict building codes in place since 1935 (link to frequency of hazard). These codes are designed to ensure that buildings are protected from structural damage during moderate earthquakes, and that major earthquakes would not cause buildings to collapse. These have been updated several times since the 1930s. Unfortunately these did not take into account the risk of liquefaction undermining the strong foundations of some buildings.
NZ has a well developed hazard resilience programme, known as the Natural Hazards Platform, set up in 2009. This includes GNS (New Zealand’s leading provider of Earth, geoscience and isotope research and consultancy services), and NIWA (National Institute of Water and Atmospheric Research)
GeoNet: Provides a national network of instruments and data centres to monitor seismic activity and other hazards. Can provide information to emergency services and search and rescue within minutes of a seismic event.
what were the informal (community/popualtion) responses?
Where families had second homes, or families elsewhere children were enrolled in schools across the country
From June 2010 to June 2012, the population for the greater Christchurch area declined by 9,200 (2%).
Dozens of community organisations popped up after the earthquake to try to decentralise facilities (with the aim of providing services on a more localised basis without the need for a car or laptop). They became the voice of the people on the ground while the Government attempted to gain an overall picture of the disaster (often the information that the Government had and the reality depicted by these organisations were vastly different).
The ‘Farmy Army’ was a group of more than a thousand volunteers from the surrounding farming community who turned up to help clear the streets after the devastating liquefaction (Relief)
‘White chair’ monument to the people who lost their lives
info on the relief of the earthquakes
Full emergency action plan within 2 hours (coordinated by the National Crisis Management Centre in Wellington)
Emergency response teams, international disaster crews, community response
Rescues - all survivors rescued within 24 hours
National state of emergency issued (5 days)
info on rehabilitation
Rescue changed to response after a week (link to Park Model).
Temporary accommodation set up on the racecourse and Agricultural Park, food.
