Earthquakes-Why do some areas suffer more than others?

The main defining point of this question is where the specific area is. Whether it is situated on a boundary or close to it. Earthquakes have been experienced in areas such as England where it was assumed that no seismic activity was present here. This was until it was discovered that England has many fault lines running through the country. Other areas that have experienced earthquakes and do not lie on plate boundaries are areas known as hot spots i.e. Hawaii. From figure 3,51 in the text book it is clear that most of the seismic activity is experienced on or near the plate margins that make up the crust of the earth surface. This is due to the high activity at these points where new material is ‘created’ or ‘destroyed’. From fig 3.51 I can deduce one other aspect of earthquakes and that is that there is a far greater number of reported earthquakes on the eastern sea board of Asia which runs down throughout Indonesia and continues down most of the western rim of the pacific ocean. This high concentration continues down the western coast of South America. These high frequency of earthquakes is in direct proportion to the mid Atlantic ridge where the north American plate is diverging from the Eurasian and the south American plate is diverging from the African plate. The question is why is there such a noticeable difference in the frequency of earthquakes at these plate margins. The answer lies in the type of activity that is being produced from the plate movement at these points. This theory all ties in to the volcanic activity that is present at these plates. On the mid-Atlantic ridge where the plates are diverging lava is easily deposited on to the surface without a great amount of force required in comparison to destructive margins, this therefore correlates to the lower numbers of earthquakes. Destructive margins on the other hand create much stronger forces, as one of the plates becomes subducted under the other. This requires tremendous amounts of energy, which are released as earthquakes. This correlates to high number of earthquakes at destructive plate margins as higher energies are exerted. This is also the case with conservative plate margins. Destructive and conservative plate boundaries are more likely to have a high frequency and magnitude than constructive margins due to the different energy levels produced. This is important because we can now estimate areas that are going to be under larger threats from violent earthquakes and which are not. From the above I can determine that areas near conservative and destructive plates are going to under a larger threat than areas along constructive plate margins.

Apart from the geological features such as plate boundaries the other main reason why different areas suffer in different ways comes down to human influences, for example, development and the hazards associated with developed and developing areas. Some places are considered to potentially suffer more because there is a far greater risk for people and property. If an earthquake was to hit an urban area the chances of damage from the hazard are greater than that if the earthquake struck in the countryside for example. This means the urban area would suffer more. There are many other factors, which do ...

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An Earthquake, which measured 8.4, killed fewer people than one that measured 7.8. This next point refers to the human influences. If I said that one of the above earthquakes occurred in an LEDC and one in a MEDC it would probably become much clearer as why the deaths were disproportionate to the magnitude of the earthquake. In an LEDC the people where unprepared for such a disaster. This may be because the country has neither the money nor technology to do so. From previous work I know that the highly dense populations of LEDC cities along with cheap building construction probably played a major role in most of the deaths.

The LEDC IM referring to is turkey. An earthquake struck the industrial city of izmits in 1999 killing thousands. Many died in buildings that were poorly and cheaply constructed. These buildings would have shook like jelly on the weak foundations of soft rock soils. This was accompanied by the absence of earthquake drills and high density cheap housing to cause a humanitarian disaster zone. The lack of preparedness caused destruction of industry that will mean the prosperity of the city will suffer in the long term. This area in particular would have suffered greatly in both in the short and long term.

The other earthquake struck anchorage, Alaska in 1964 killing a few hundred. The government here was under knowledge of the threat and acted accordingly by preparing the people and buildings with stringent construction criteria and building low-density housing.

Apart from physical characteristics many areas prone to earthquakes suffer more due to the inability of authorities to act and protect areas at threat. Earthquakes are a potential threat anywhere on the globe but this threat is enhanced due to geological features such as positions in relations to plate boundaries. The effect that Earthquakes have is one that can be determined by people by taking the neccercary precautions. Areas experiencing earthquakes will always suffer but the degree of suffering will depend on the position of the area, the precautions that have been taking by the authorities, building criteria, and a new idea that has been introduced, land management. This idea is taken on board from flood prevention by placing areas that are less effected by flooding near the river i.e. farmland and areas that would be damaged considerably (property) away from the river channel itself. This idea could mean that areas prone to earthquakes would build low density housing near the area most at risk.

Alex Robinson