Geography essay – earthquakes Essay
Geography essay – earthquakes
At a conservative margin two plates try to slide past each other slowly. Quite often, the two plates stick and pressure builds up; the release of this pressure creates a severe earthquake. There are no volcanic eruptions along conservative plate margins because the crust is neither being created nor destroyed. The classic example of a conservative plate margin is the San Andreas Fault in California. The North American and Pacific Plates are moving past each other at this margin, which is the location of many earthquakes.
These earthquakes are caused by the accumulation and release of strain as the two plates slide past each other. The vast majority of Earthquakes occur along plate margins. In fact the locations of the earthquakes and the kind of ruptures they produce help scientists define the plate margin. Many earthquakes form a narrow spread at some plate margins than others; generally speaking, the earthquakes at destructive plate margins have a greater spread and therefore affect more places than at conservative plate margins.
According to plate tectonic theory, huge slabs of plates are in constant movement caused by convection currents, a lot of pressure builds up at the plate margins, which when released causes a sudden jolt or earthquake. This accounts for a large number of earthquakes that occur at plate margins. The fact that the most deadly earthquakes occur at destructive/transform plate margins suggests that greater pressure builds up than at constructive plate margins. Earthquakes are probably the most frequent of all hazards, yet their impact on people, property and communities varies from one place to another.
When it comes to buildings the type of building materials and designs used can minimize loss of life, mainly in wealthy areas. This was the case with the Loma Prieta earthquake where very few people were killed, however in some areas were more vulnerable with older buildings. With the Kobe earthquake (1995) there were less strict building regulations which led to high death toll of over 6,300. In poorer parts of the world building design is often inadequate, even though building design standards are in place they are rarely enforced, which was the case for Mexico City (1985).
Here several modern high rise buildings collapsed as concrete crumbled and the thin steel structures tore apart. The central hospital just collapsed in total killing around 30000 people. It can also have different effects on different parts of the world due to the frequency of the earthquake and the levels of development. In wealthy areas where earthquakes are common, such as California and Japan, a lot is done to prepare for an earthquake; there are regular earthquake drills in schools and offices.
Poorer countries tend to be less well prepared this is partly due to the lack of money to invest in materials and educational programs. Also because earthquakes are perceived as infrequent problems in a society facing daily struggles for survival. It is often said LEDC’S suffer much more from the effects of earthquakes than MEDC’s which is true in terms of human costs. A poor country with UN sturdy buildings and its inability to cope with the after effects of an earthquake, will suffer greater loss of life, homelessness and loss of livelihood than a rich country.
In recent years some of the greatest earthquake disasters have occurred in LEDC’S including India 1993 which killed 10,000 people, Afghanistan 1998 which killed over 6,000. MEDC’s do not tend to suffer as much human loss, but they do suffer a lot of financial loss, as insurance companies and governments re-fund building programs and pay compensation. Afghanistan 25th March 2002 there were a series of earthquakes that lasted 10 hours and killed 800-1000 people, injured 4,000 and left 20,000 homeless. Towns were flattened the earthquake only measure 6. 1 on the Richter scale.
There were a few reasons why this earthquake caused so much widespread disaster. The region is remote and very poor, after suffering droughts and wars they have no resources left to cope with such an earthquake. The houses were very poor and couldn’t withstand the shaking; much housing had heavy roofing to insulate their houses which just collapsed killing people inside. Although the earthquake was not so powerful it was a shallow one occurring at a depth of 8km. Now comparing it with a wealthier place you can see the difference that money can make and buildings.
Taiwan 30th March 2002 measured 7. 1 on the Richter scale so was more powerful than the Afghanistan one, and was at 10km deep so again was shallow; this earthquake only killed 5 people. The Taiwan earthquake was significantly more powerful than the Afghanistan earthquake yet it caused far less loss of life, this was due to the fact that, many of the buildings were modern and coped well with the ground shaking, people were also aware of the dangers and had prepared themselves to minimize the dangers and damage to the properties.
Taiwan is significantly wealthier than Afghanistan and it’s therefore better able to prepare and then to react after an earthquake. In conclusion 2 earthquakes of a similar magnitude might be expected to have similar effects but this is not always the case. Whilst there can be no doubt that a big powerful earthquake will caused a lot of damage wherever they occur, it seems to be the case that all things being equal LEDC’s tend to suffer more than MEDC’s.
Subject: San Andreas,
University/College: University of California
Type of paper: Thesis/Dissertation Chapter
Date: 8 September 2017
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