Cause of Earthquakes and relation to the cause of New Zealand Earthquakes:
Tectonic plates are broken up pieces of the Earth’s outer crust, which are the reason why earthquakes occur. These plates move regularly but extremely slowly. The different ways plates meet and diverge at boundaries and they are called divergent boundaries, convergent boundaries, transform boundaries and subduction boundaries After there is movement within tectonic plates for a long time, it causes a lot of stress and tension. An extreme amount of pressure is released from the fault line in between plates and the plates move towards each other, converge from each other or move sideways against each other. At this point, an earthquake occurs as seismic waves form from a focus in the fault line or a fracture in a fault and energy radiates outwards in all directions. If the earthquake is oceanic, a tsunami is likely to form from the seismic waves but if it is a continental earthquake, the land will start to shake. When the seismic waves reach the earth’s surface from the crust, it will then cause buildings and structures to shake. The amount of seismic waves depends on how much energy was released. This then determines the magnitude of earthquakes.
Since New Zealand lies in between the Australian Plate and the Pacific Plate, it suffers from many earthquakes since there are a lot of faults or fractures along these plates; The major faults are the Alpine Fault and the Wellington Fault. It is unfortunate that the New Zealand land mass is situated in between two tectonic plates which is the main reason why so earthquakes occur. Every year the country has thousands of earthquakes, but only around 200 big enough to be felt.
Process of Earthquakes:
The tectonic plates move by the methods of divergence, converging, subduction and transform and if this occurs over a long period of time, pressure builds up and is released in the form of seismic waves which therefore creates an earthquake. The process when an earthquake occurs is that a sudden jerking movement happens between the 2 plates for which then creates severe movement in the ground or ocean above. This shaking generally lasts for less than 40 seconds. Primary waves radiate in all directions from the epicentre of the earthquake. There are three different types of seismic waves released they are primary waves, secondary waves and long waves. Primary waves travel very rapidly. Although they are the first waves recorded by instruments such as seismographs, they do very little damage but, secondary waves travel through solids. Secondary waves can cause the ground to vibrate extremely both horizontally and vertically. Waves which are slower than primary waves and secondary waves are called long waves which are also very harmful.
Effects of Earthquakes:
Ground shaking is caused by seismic waves passing through land especially areas near the epicentre where most damage is likely to happen. The amount of ground shaking depends on how stable the ground is, whether it is on solid bedrock or loose sediment. It also depends on the strength of the earthquake and how long it lasts for, and the distance in which the seismic waves travel. When an earthquake is strong enough to cause the ground to rupture, infrastructure built will collapse. Ground ruptures can only occur where there is a fault line. Shaking of the ground may trigger avalanches, landslides and rock slides. Some landslides and avalanches can be more damaging than the initial effects of the earthquake. There can be damage to man-made structures. Bridges, buildings, dams, roads and other infrastructure from ground shaking can be damaged. Materials used does usually affect the amount of damage a building received.
During earthquakes, fires can start from broken electrical and gas lines which is a common side effect. The gas released from broken gas lines can be fuel for a fire which started from a small spark such as a broken light bulb. As most water and plumbing lines will also be broken, it is hard to find accessible water during a fire at the time. Factories and power plants affected by the earthquake can release toxic chemicals which can pollute the atmosphere and the area around it which can have a harmful effect on society. Radioactive pollution from damaged nuclear power plants can affect the societies extremely as there are many health issues which can be present if people are exposed a large amount of radiation.
There can be liquefaction of the land. Liquefaction occurs when the sturdiness and hardness of soil is decreased by the tremors released from an earthquake. It has the same effects as quicksand. If liquefaction occurs on land, it is hard to rebuild on in the future. Tsunamis are one of the worst effects of an earthquake. They are often formed from earthquakes occurring in the oceanic crust. They can sweep away buildings and people.
Extent of the impact of earthquakes on society:
The growth of population and urbanisation of New Zealand, especially in earthquake prone areas, can be suggested to be directly linked to the astounding impacts on humans and its environment during this disaster and will only increase in the following decades. Recent earthquakes around New Zealand have illustrated the only increasing mortality rate and the detrimental affects it has on health and safety and properties within the area.
There are a number of factors that need to be said to fully be able to understand the extensive damage that earthquakes can have on the population, such as magnitude, how densely populated the affected area is, the level of earthquake disaster preparedness and the mitigation measurements enforced. On February 2011 at 12:51pm, Christchurch was hit with a magnitude 6.3 earthquake, taking the lives of 185 people and seriously injuring 164 people. Essentials such as roads, bridges, water pipes, power lines, cell phone towers and phone poles were damaged or broken. Several minutes after that, there were 10 aftershocks felt, each with a magnitude of 4 or more debilitating already weakened buildings. As a result of that earthquake alone, two major buildings collapsed and up to 100 000 buildings were damaged and around 10 000 had to be demolished.
Those 185 lives lost represents the mothers, fathers, uncles, aunts, grandparents, friends and neighbours that were taken by a force that even the strongest machines break under. Those 100 000 buildings that were damaged and the 10 000 that had to be demolished hold the memories lost, but this is only a small glimpse into the world of an earthquake prone area. Although contributing factors may change slightly, the effects remain the same. The deaths, injuries and economical burdens of a natural disaster such as earthquakes is always going to impact society but it depends on how much it effects them.
There are a number of factors that need to be said to fully be able to understand the extensive damage that earthquakes can have on the population, such as magnitude, how densely populated the affected area is, the level of earthquake disaster preparedness and the mitigation measurements enforced. On February 2011 at 12:51pm, Christchurch was hit with a magnitude 6.3 earthquake, taking the lives of 185 people and seriously injuring 164 people. Essentials such as roads, bridges, water pipes, power lines, cell phone towers and phone poles were damaged or broken. Several minutes after that, there were 10 aftershocks felt, each with a magnitude of 4 or more debilitating already weakened buildings. As a result of that earthquake alone, two major buildings collapsed and up to 100 000 buildings were damaged and around 10 000 had to be demolished.
Those 185 lives lost represents the mothers, fathers, uncles, aunts, grandparents, friends and neighbours that were taken by a force that even the strongest machines break under. Those 100 000 buildings that were damaged and the 10 000 that had to be demolished hold the memories lost, but this is only a small glimpse into the world of an earthquake prone area. Although contributing factors may change slightly, the effects remain the same. The deaths, injuries and economical burdens of a natural disaster such as earthquakes is always going to impact society but it depends on how much it effects them.
Impact on the lithosphere, biosphere, atmosphere and hydrosphere:
Lithosphere:
The lithosphere is the solid upper part of the earth made up of the upper portion of the mantle and the crust. The lithosphere is rigid despite the rocks that make it up are considered flexible. It is also thought to be the coolest layer of the earth as it able to conduct heat through the the processes of convection due to its plastic mantle underneath the lithosphere. When earthquakes occur on solid sedimentary rocks, it often soften the effects but when they happen on less compacted rock, damages to buildings is likely which also includes falling power lines and infrastructure destruction. These quakes that occur on less compacted rock may also cause fires and deaths and injuries.
Biosphere:
This is the regions of the crust, waters and atmosphere where life exists. The biosphere includes up to the highest mountains, thousands of kilometres above sea level, to the lowest depths of the seas. However this is the extremes, in reality, the upper parts of the atmosphere have very little oxygen which is essential for life with very low temperatures and the bottoms of the oceans are often very dark and cold. It is often said that the biosphere is just the peel of an apple in relation to its size. The intense movement in an earthquake can cause severe damage to properties and the natural environment whilst also accountable for the loss of life. Although, it must be made clear that the earthquake in itself doesn't harm life, it is when building and objects start collapsing and falling.
Atmosphere:
The atmosphere, it’s the only thing keeping you from burning up everyday from ultraviolet radiation. How it does this? Well a collection of gases, 78% nitrogen, 21% oxygen, 1% water vapour to soak up the ultraviolet radiation from the sun, while warming the earth through heat retention. It also provides essential rainfall whilst holding the oxygen needed to survive. In a nutshell, the atmosphere is the collection of gases needed in order to make life on earth habitable. Earthquakes are known to indirectly enhance the greenhouse effect as the strong movements in the ground release pockets of methane, a gas that contributes to the greenhouse effect. Methane, along with carbon dioxide, absorb the suns radiation and traps it under the atmosphere thus increasing the overall temperature.
Hydrosphere:
The hydrosphere consists of the total amount of water on the earth, whether it be on the ground, under the ground or in the air. It can also be in different forms such as liquid, ice or vapour. The hydrosphere works in a cycle, the water cycle, water collects in clouds which then falls to earth in the different forms of precipitation such as rain or snow. It then collects into rivers lakes or oceans that may be evaporated to start the process all over again. If the earthquake originated from beneath the surface for which is known as a submarine earthquake, can cause a tsunami which can potentially turn into a serious catastrophe. There is also the real possibility that both confined and unconfined aquifers can be affected. Although the risk is there that an unconfined aquifer may get contorted, there is a greater chance that a confined aquifer may be deformed due to the intense movement of the earth. Also, the groundwater level may change with the effects evident in both types of aquifers. Also, a large effect to the hydrosphere is through tsunamis as this can interrupt some oceanic communities and if a tsunami reaches land this can strongly affect those inhabiting on land.