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Saturday, January 14, 2012

Earthquakes: impacts and management

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Sudden release of stresses built up in the earth’s crust cause shaking of the earth- surface. It is called as earthquake. The earth quake may range from mild tremor to a large scale movement of earth causing extensive damage over a wide area. The location of the epicenter is expressed by latitude and longitude.

The intensity of an earthquake is measured on Richter scale, which was devised in 1935 by Charles Richter of California Institute of Technology, U.S.A. An earthquake measuring more than 5 on Richter scale (usually 7 and above) causes great damage. The place of origin of an earthquake is called as its focus or the hypocenter where as the point on the earth surface vertically above the Focus is called as Epicenter.  Earthquakes cause physical, biological, economic and environmental damages. The intensity of an earthquake is calculated through Mercalli Scale, by assessing the damage caused by an earthquake. This Scale was invented by an Italian Seismographer named Giuseppe Mercalli in 1902.

How do earth quakes originate?
The surface of the earth is made up of huge rocks, called as plates. These plates remain moving slowly. Some times their movement is gradual. At other times, plates get locked with each other. Thus the energy created by their movements remains accumulated at a certain place. When the accumulation of this energy grows stronger, the plates break free and snap into a new position. The vibration thus produced causes plates to develop cracks, shake and fall. The fractures thus caused, in the crust of the earth are called as faults. If all the stress has not been cleared, more after shocks or trembling can occur in the fault zone. The point on the earth’s surface which is directly above the Seismic Focus of the quake is called as epicenter.

Impacts of earthquakes
•Since, earthquakes cause shaking and trembling of earth crust, they cause big buildings to fall down. As a result hundreds of people and cattle are crushed to death. Earthquakes cause heavy losses of properties also.
•Earthquakes can destroy everything causing total devastation.
•Buildings are shifted off foundations, ground cracks up, and underground pipelines are damaged.
•Earthquakes cause land slides in hilly areas, and Damage to lines of communications electricity supply.
•Bridges and roads are damaged badly and rail-lines are twisted out of shape.
•Earthquakes generated by undersea tremors create towering walls of water having great powers of destruction. In Japanese language, these strong waves are called as TSUNAMIS.

Management and Mitigation of Earth Quakes
These strategies comprise main and community based activities mentioned below-
•Contractors and developers of building constructions must follow norms fixed for buildings. Buildings must not be built on soft soils.
•Buildings should not be constructed in vulnerable areas and those that have already been built in such areas should be strengthened properly.
•Use of standard quality building materials and following Indian Standards Codes for building constructions should be kept on priority.
•Human habitations at high risk zones should be shifted elsewhere.
•People should be made aware of dos and don’ts about earthquakes and important lifeline buildings should be strengthened to accommodate people after the earth quake. Hospitals and Fire services should be upgraded.
•Community should be prepared and educated for mitigating impacts of earthquakes.
•Community based Earthquake Risk Management Projects should be developed. Retrofitting of school buildings and other important buildings, purchase of Emergency Response Equipments etc. should be the principal activities of such projects.

Key Words : disaster, earthquake, risk, management, risk zones

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