Disasters can be categoried as natural and man-made disaster.
Natural disaters are caused by forces of nature, which are powerful and uncontrollable and occur suddenly. These events occur due to Earth's natural process. Such disasters can cause severe damage to life and property.
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Earthquake : An earthquake is a sudden release of energy accumulated in deformed rocks which causes the ground to tremble or shake.
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Seismograph : It is an instrument which measures and records vibrations of an earthquake.
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Richter Scale : Richter scale is the scale having 0 to 9 range used to measure the magnitude and intensity of an earthquake. One point increase represents 10 times magnitude of the earthquake.
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Landslides : Sliding of mass of rock, earth an debris which move down a slope of a mountain by their own force and weight are termed as landslides.
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Debris flow : Flow of debris in the Western Ghats of kerala down the slopes is called debris flow.
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Floods : Floods are temporary inundation of large areas due to an increase in reservoir or due to rivers flooding their banks because of heavy rains, cyclones etc.
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A Cyclone : A Cyclone is a violent storm, often of vast extent, characterised by high winds rotating about a calm centre of low atmospheric pressure.
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A Drought :A drought is an insidious natural hazard that results from a departure of precipitation over a season or longer period of time, insufficient of meet the demands of human, plant and animal activities.
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Watershed : Watershed is the geographic area where water flows to a common point.
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EARTHQUAKES :
Definition : An earthquake is a sudden release of energy, which has accumulated in deformed rocks, causing the ground/earth to tremble or shake.
• Onset Type and Warning : Earth quake onsets suddenly. They occur at any time, day, night and at any time of the year. They occur all of a sudden without any advanced warning. Their impact is sudden. Earthquakes cannot be predicted despite extensive researches and investigation in recent decades.
• Elements at Risk : The following elements are at risk during earthquakes
1. Settlements : Settlements in earthquake prone areas-built on alluvial and wind blown soil deposits. Settlements built in landslide prone areas. Settlements built along geological fault lines.
2. Buildings : Weak and having high occupancy. Traditionally built using earth, rubble, bricks by masons. Buildings with heavy roofs. Buildings with poor quality material. Buildings with poor maintenance. Buildings with weak and flexible storage.
• Typical Effects Of Earthquakes :
1. Physical Damage : Damage of building Damage to service structure Fires due to short circuit Floods due to dam failures. Landslides, in hilly and mountainous regions.
2. Casualties : Very high near the epicentre Very high in thickly populated areas. In buildings. which are not earthquake resistant.
3. Public Health :
• Multiple fracture injuries.
• Moderately and most severaly injure
• Break down in sanitary conditions
• Unhygenic conditions leading to spread of epidemics.
4. Water Supply :
• Failure of water supply/distribution system, water supply network.
• Failure of fire hydrants and non control on fires.
5. Transport Network :
• Breach in roads and railway lines.
• Failure of airport run ways.
• Collapse of related infrastructure.
6. Communication :
• Failure and collapse of transmission towers, transponders
•Disconnection of telephone and telegraph lines.
• Damage to telephone exchange
7. Electricity :
• Failure of transformers
• Breaking of electric wires network
MAJOR MITIGATION STRATEGIES REGARDING EARTHQUAKES
Engineered Structures :
• Buildings to be designed and built to withstand ground shaking.
• Architectural and engineering inputs to be put together to improve building design and building practices.
• Intensive analysis of soils before starting construction.
• No construction of buildings on soft soil.
• Building codes and guidelines to be enforced strictly. The Bureau of Indian Standards publisher these codes and guidelines.
• Municipality to check the building plan thoroughly before starting construction, as per building bylaws. Building design should satisfy all building bylaws for safety and comforts.
• Existing big buildings such as hospitals, schools and fire stations should be upgraded by retrofitting techniques.
• Architects, buildings, constructors, designers, engineers, fmanciers, government, functionaries, houseowners and masons should be given training to sensitise them. This will create public awareness.
• Construction of building should be avoided in the areas prone to fires, floods, landslides, earthquakes and cyclones.