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The main effect of an earthquake is the horizontal forces that are generated in the structure. The horizontal ground accelerations give a measure of this force. The granular soils get compacted due to the vibrations. This in turn causes the settlement of the ground surface. Another effect of the vibrations is liquefaction. The degree of liquefaction depends on the relative density of the soil, percentage of fines, depth of water table and the ground acceleration.
Earthquakes occur due to movements along faults that have evolved through geological and tectonic processes. Often they occur without any prior warning and are, therefore, unpredictable. The large area of India is prone to earthquake. The construction of earthquake resistant building is the only solution for safeguarding our urban centres from the menace of earthquakes. Here are some effects of the earthquake ;
- The dynamic stress and induced pore water pressure may reduce the bearing capacity of the soil
- Loose granular soils are compacted by ground motion. This causes large subsidence of the ground surface.
- Compaction of loose granular soil may induce excess pore water pressure, which causes liquefaction of soil
- The vibration due to earthquake may cause structural damage
The natural disasters like earthquake can not be prevented, but measures are required to be taken to reduce the extent of damage, especially in a vast country like India which is the 2nd largest populated country of the world supported by low level infrastructure and inadequate resources. High levels of risk combined with low levels of coping mechanisms result in major disruptions or loss of lives and livelihood.
The developed countries of the world are adopting new technique of construction of seismic proof buildings whereas under developed countries do not give much attention for the construction of seismic proof buildings due to shortage of resources. With the result world’s worst disasters always take place in underdeveloped and poor countries. Disasters cause enormous destruction and human sufferings. The losses due to occurrence of earthquakes reduce the pace of economic development and often lead to depletion of available resources.
The developed countries of the world are adopting new technique of construction of seismic proof buildings whereas under developed countries do not give much attention for the construction of seismic proof buildings due to shortage of resources. With the result world’s worst disasters always take place in underdeveloped and poor countries. Disasters cause enormous destruction and human sufferings. The losses due to occurrence of earthquakes reduce the pace of economic development and often lead to depletion of available resources.
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| Sichuan earthquake of May 2008 |
Recommendations for the Earthquake Zone ;
The earthquake disasters can be averted with the construction of seismic proof buildings. Each building can be designed in such a way that it may withstand during severest quakes depending on the seismic zone it falls in. “The National Disaster Management Authority” (NDMA) has made it compulsory for all new constructions to be earthquake-resistant, especially in cities located in seismic zones. The guidelines have also recommended selective seismic strengthening and retrofitting of existing priority structures located in high-risk areas.
It has also been proven that well maintained buildings have faired better than those in poor condition during and after an earthquake. Thus, maintenance and seismic retrofit are two critical components for the protection of historic buildings in areas of seismic activity. It makes no sense to retrofit a building without improvements. The subcontinent is sitting on the highly seismic Indian plate, with some major faults lines. In fact there is no seismically safe zone in India. Disasters have left the 800-year-old Qutub Minar with a slight tilt but it has survived several quakes in its lifetime.
• Implementation of Disaster Management Plan
The Disaster Management Bill, likely to be presented in the winter session of Parliament, will make it necessary for all states to have a disaster management authority and implement the national disaster plan. “Eventually disaster management is a state’s concern and the action plan has ultimately depend upon the state’s own concerns and ability to set up institutional and financial.
• Creation of Special Force At National Level
At the national level, other measures are being planned. Eight battalions of 10,000 soldiers are being trained for being posted to eight different locations and money has also been sanctioned for buying aircraft for their use in cases of emergency.
• Creation of Emergency Operation Center
It is being equipped with state-of-the-art communication links and micro-zonation of 38 cities above 10-lakh population is being attempted in different phases. The micro-zonation of Delhi has just been completed. In words of Science and Technology Minister Kapil Sibal, the micro-zonation process is the government’s effort to take effective measures with proper research to minimize risk to existing buildings in the event of an earthquake.
The earthquake disasters can be averted with the construction of seismic proof buildings. Each building can be designed in such a way that it may withstand during severest quakes depending on the seismic zone it falls in. “The National Disaster Management Authority” (NDMA) has made it compulsory for all new constructions to be earthquake-resistant, especially in cities located in seismic zones. The guidelines have also recommended selective seismic strengthening and retrofitting of existing priority structures located in high-risk areas.
It has also been proven that well maintained buildings have faired better than those in poor condition during and after an earthquake. Thus, maintenance and seismic retrofit are two critical components for the protection of historic buildings in areas of seismic activity. It makes no sense to retrofit a building without improvements. The subcontinent is sitting on the highly seismic Indian plate, with some major faults lines. In fact there is no seismically safe zone in India. Disasters have left the 800-year-old Qutub Minar with a slight tilt but it has survived several quakes in its lifetime.
• Implementation of Disaster Management Plan
The Disaster Management Bill, likely to be presented in the winter session of Parliament, will make it necessary for all states to have a disaster management authority and implement the national disaster plan. “Eventually disaster management is a state’s concern and the action plan has ultimately depend upon the state’s own concerns and ability to set up institutional and financial.
• Creation of Special Force At National Level
At the national level, other measures are being planned. Eight battalions of 10,000 soldiers are being trained for being posted to eight different locations and money has also been sanctioned for buying aircraft for their use in cases of emergency.
• Creation of Emergency Operation Center
It is being equipped with state-of-the-art communication links and micro-zonation of 38 cities above 10-lakh population is being attempted in different phases. The micro-zonation of Delhi has just been completed. In words of Science and Technology Minister Kapil Sibal, the micro-zonation process is the government’s effort to take effective measures with proper research to minimize risk to existing buildings in the event of an earthquake.
Micro-zonation, he says, will help bring area-wise changes in building bylaws to ensure quake resistant measures in the structural designs of high rises to minimize the risk of heavy damage and loss of life in event of an earthquake. While the government is attempting a paradigm shift in the disaster management from relief and rehabilitation to mitigation and prevention, to make it successful will eventually depend upon the civil society. You can find other information about the construction of earthquake resistent buildings in seismic zones of india at townplanning.in
