Christchurch Earthquake Essay

On Tuesday 22nd of February 2011 thither was a 6.3 magnitude humanityquake at 1251pm. The damage in Christchurch was farthest much(prenominal) substantial than the damage caused in the 7.1 cosmosquake only 5 months before. 185 people were killed in the February body politic quake and thou brinystays more than(prenominal) were injured. The epicentre of the priming coatquake was very close to Lyttelton and only 10 kilometres out from Christchurch Central city. The intermission line that ruptured and caused the earth quake was the 15 kilometre shift on the southern edge of the city from Cashmere to Avon Heathcoat estuary.The build-up of stress or pressure sensation in the rocks below Christchurch The earth is made up of many architectonic platefuls. It is the effect of these plates that has created the geographical features of many countries. New Zealand lies on the boundary between 2 of these plates The Pacific Plate and the Australian Plate. This boundary is most obvi ous on the Southern Alps. From this main duty period there argon many little ones spreading outwards. Some of these spread into Canterbury. Before the 2010 and 2011 earthquakes it was non thought that there were any signifi give the bouncet breach lines near Christchurch. Now we know there argon. Stress is not caused by the causal agent of tectonic plates, but more by when the edges of the plates jam against each former(a) and stop moving. The pressure builds up behind the part that has jammed. Eventually the pressure is so great that the plate lasts suddenly and this causes earthquakes.The build-up of stress and the sudden movement when the stress is released shakes the rocks deep below Christchurch. The fault lines under and near the city shake, causing the rocks to move. This causes the major earthquakes.The out core of the earth is layer of molten rock. On top of this is the cortex. On top of the mantle is the earths cheekiness that we live on. The mantle gets very warm and in thin places molten rock rises to its top. Because of this hot and cold relationship, the crust on top is broken into tectonic plates. The movement of molten rock causes heartiness to be moved upwards into the crust. When the crust can no longer hold this vim, it moves along the boundaries of the tectonic plates. These boundaries ar the weakest parts of the crust and exit therefore be the first bits to falling out and move.Release of stressThe Port Hills fault line that caused the 6.3 magnitude earth quake in February was 15km long and stretched east to north east along from Cashmere to the Avon Heathcoat estuary. The fault line that caused the Feb 22 quake was one that was previously incomprehensible close to the Port Hills. This fault line did not break the earths surface, so there was nothing visible for scientists to go and boldness at. Using instruments that measure earthquakes and earth movement scientists were able to determine hardly where this fault was an d that the bit that actually moved, causing the earthquake was 15km long. Fault lines atomic number 18 the weakest part of the earths crust. When there is stress caused underneath by movement, the fault lines are the first part to move. It is a bit wish a piece of glass if there is a crack in the glass that will be the first place where the glass will break. So pressure is released under the earths crust. The earths crust will actually hold a lot of this pressure. When the pressure becomes too much for the crust to hold, the fault lines are the first bits to move. sensation of the ways scientists measure and record the fault movement was through the transmutation of GPS stations, whose displacements were used to create the fault slip model.http//www.gns.cri.nz/Home/Our-Science/Natural-Hazards/Recent-Events/Canterbury-quake/Hidden-fault The transmission of goose egg through the earths crustThe energy released when a fault line moves is similar a stone being dropped in a puddle of piss. It causes ripples to move out from the centre. The ripples are worst nearest the centre and they get small as they get to the edge of the puddle. The centre of an earthquake is the epicentre. When energy is released at an epicentre, waves of energy move outwards, causing the ground to shake. As the epicentre of the Christchurch earthquakes was quite an close to the city, the energy that caused the ground to move under Christchurch was violent. If the epicentre had been save away the quakes would hold back felt littler.There was movement up, d throw and sideways during the February quake. The baffle of land on the south side of the fault line lift about 2.5 metres this included the Port Hills. The land on this side of the fault also moved westwards. The land on the north side of the fault moved eastwards towards the sea.However, much of this movement was underground. The land has rise as much as 40 centimetres around the western side of the Avon-Heathcote estuary.Th e totality the Port hills has travel varies a lot , under Lyttelton Harbour it has risen about 5 centimetres but at the base of the hills near the Heathcote valley, it has risen to a maximum of around 25 centimetres. As a expiration of the fault slip, areas like Bexley, Aranui, Wainoni, Avondale and New Brighton subscribe sunk, mostly by slight than 15 centimetres. Northern, northeastern and central areas of Christchurch have also sunk, but broadly by less than 5 centimetres. Earth quakes / fault movements are metric with a sensitive instrument called a seismograph. Earth quakes generate seismic waves and the seismograph is used to detect them.The magnitude of an earthquake depends on how big or small the fault is and the amount it has slipped. The seismograph shows the recordings made on the seismographs detected at the surface of the earth to determine how large the earthquake was. A goldbrick wiggly line that doesnt move very much authority a small earthquake, and a long wiggly line that wiggles a lot means a large earthquake. Through the seismograph we get the Richter plateful. The Richter scale is a scale used for expressing the magnitude of an earthquake based on the height of the largest shake 100km from the epicentre. There are different types of seismic waves that can be detected there are P waves and S waves (primary and secondary) P-waves are travel at the greatest velocity through the earth qualification them the first waves to be recorded on a seismograph during an earthquake. S waves are transverse waves that travel slower than P waves but are more destructive because of their large amplitude.The effects on man-made structures and after piquesLiquefaction is a burden where strength and stiffness of a defect is reduced by tectonic plates shifting or other rapid movement. Liquefaction cash in ones chipss in sodden soils. The water applies a pressure on the soil particles this controls how tightly the particles are press together. Before an earthquake, the water pressure is relatively low. However when the tectonic plates pass shaking it can cause the water pressure to build up to the point where the soil particles can readily move. Some Areas of Christchurch are more accustomed to others as nearly suburbs have up to 9cm of liquefiable substances much(prenominal) as sand and spongelike soil. These substances turn into liquefaction easily as they desegregate well with the water underground. costal areas are also more prone as the soft sand mixes well with the water also. There was more damage caused by liquefaction in the central city and eastern suburbs than other places simply because it depends on the soil. Since Christchurch is built on marsh land our soil is very susceptible to liquefaction and there is very little we can do to stop it. Some Areas of Christchurch are more prone to others as some suburbs have up to 9cm of liquefiable substances such as sand and soft soil.These substances turn int o liquefaction easily as they mix well with the water underground. Costal areas are also more prone as the soft sand mixes well with the water also. Most buildings that survived the Christchurch earth quake were timberen because when wood is shaken it is able to bend and twist with the movement, whereas for bricks and stone they cant move at all and just have to absorb the shock of the shaking which generally leads to buildings collapsing all together E.g. Christchurch Cathedral, CTV building and Knox church. Buildings like the Christchurch Womens Hospital survived through the September and February earthquake because its foundations are base isolated. prat isolation is when a building is separated from the ground that it is built on. tremendous plates separate the ground and the building. One plate is secured to the ground and the other is secured to the toilet of the building. During an earth quake these plates only move a little bit, take up most of the shock from the earthq uake minimizing damage to the rest of the building.Also depends on the soil under the building, if it is prone to liquefaction or not. Some houses had liquefaction coming up through their floors damaging the foundations so much they had to leave their homes, and basements of office buildings or apartment blocks were flooded with liquefaction, making them un-use able.A tsunami didnt occur after the Christchurch earth quake because the epicentre was in land and no seismic energy was released under the sea. Tsunamis only happen when the epicentre is in the sea, making the energy from the earth quake ripple the water on to land. The bigger the earth quake is, the bigger the tsunami.Aftershocks?After shocks are a lots of smaller earth quakes that happen after the initial earth quake. They occur because the fault line that ruptured needs to settle down again and release stress, aftershocks are the fault lines way of releasing remaining energy. According to http//www.christchurchquakemap.c o.nz/february there have been 8673 after shocks since February 22nd 2011 as of Monday 19th May 2014. Including after shocks that have been so big they are classed as an earth quake of their own like the 13th of June 2011 and the 23rd of December 2011. After shocks do not occur in the exact same place, but they do occur along the same fault line and in the same region. The main earthquake has already happened and released most of its energy already, but further along the fault line the rocks are now out of place and the crunch between them causes more earthquakes (aftershocks).Bibliographyhttp//www.ipenz.org.nz/IPENZ/forms/pdfs/ChChFactSheets-Answers-critical-questions-buildings.pdf http//keithwoodford.wordpress.com/2011/02/27/understanding-the-christchurch-earthquake-building-damage/ http//scienceblogs.com/startswithabang/2013/05/10/where-does-an-earthquakes-energy-come-from/ www.scoop.co.nz/stories/SC1103/S00054/the-canterbury-earthquakes-scientific-answers.htm http//www.mona. uwi.edu/earthquake/quickinfo.phphttp//all-geo.org/highlyallochthonous/2011/02/magnitude-6-3-earthquake-rocks-christchurch/http//www.gns.cri.nz/Home/Our-Science/Natural-Hazards/Recent-Events/Canterbury-quake/Hidden-faulthttp//en.wikipedia.org/wiki/Peak_ground_accelerationhttp//www.scoop.co.nz/stories/SC1103/S00054/the-canterbury-earthquakes-scientific-answers.htm http//file. hurtle.co.nz/stuff/12-51/http//www.teara.govt.nz/en/historic-earthquakes/page-13