EarthQuake

Category: Articles/Opinion
Written by: peregrine ...... (on November 02, 2008 - 12:13 AM)

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You must have been hearing alot about the eathquake now a days as it has recently ,again, struck Pakistan. The question is how this Eathquake occur and what can be the measure taken to lessen the amount of destruction caused by it.
Due to the complexity of this topic only major things will be explained in the following lines.

First you all must know that there are tectonic plates of the earth which are dynamic (in motion). When ever these plates come in contact with each other they form a plate boundary. Earthquakes occur mostly along these plate boundaries. When maximum amount of stress is abosrbed by a colliding plate then it Ruptures releasing enormous amount of energy e.g. like thousands of atom bombs exploding simultaneously.This rupture in common life can be seen when you bend a ruler , it is only upto certain stress level that it can be bent after this limit it will rupture. This rupture releases energy in the form of heat, sound and light . This energy is not released all at once instead it is released in short bursts giving rise to aftershocks. This energy travles in the form of waves (elastic waves). These waves are generated in the subsurface and also on the surface. The major destruction is caused by the waves generated at the surface.
This was a general overlook on the mechanism if you have need any elaboration of the point than you are wel come.
Now moving towards Pakistan. The most important thing to know is that these earthquakes can not be stopped. Pakistan has been divided into 19 seismic zones out of which seven zones are dangerous with respect to earthquake. It includes peshawar karachi quetta makran and our northern areas including balakot and muzafarabad. Karachi lies in close proximity ot a triple junction (where 3 plates meet). The possibility of tsunami can also not be totally ignored. Presence of tall buildings and defected construction material used, Karachi may be a seismic risk area. Pakistan has had a notorious history with respect to earthquakes. In 1935 one great earthquake struck quetta and chaman area destroying almost 30,000 people at that time. This large earthquake was preceeded by a smaller foreshock in 1931.
Recently on oct 08 2005 another great earthquake in our northern areas killed almost one lac people.

Now after the earthquake situation is aggravated by rain which usually follows an earthquake. The reason for this is the tremendous amount of heat energy released which evaporates water and forms zones of low air pressure causing clouds to cover the effected area.
Earthquakes can not be stopped or predicted as stated earlier but in countries like china there has been some advanced testing upon it. They have applied fluid injection methods to lubricate the surfaces which eventually diminishes the possibility of stress accumulation against a fault.
But in Pakistan we are not yet able to apply this technique.
Earthquake has a return period of about 70 to 100 years. So we can expect another major Earthquake in the region of quetta witha magnitude of around 8 in 20 to 30 years and this earthquake of 6.4 magnitude may be considered as a foreshock similar to the one that struck quetta in 1931 before the devastating earthquake of 1935.

We need to strengthen our disaster management cell so that the rehibiltation process is quick. We need to establish few more seismology centers and encourage research in this field. The proper measurement of stresses accumulated and the rates of movement of plates can lead near to prediction of a major earthquake beforehand.

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