Civil Engineer Group

Earthquakes occur when energy stored in elastically strained rocks is suddenly released. This release of energy causes intense ground shaking in the area near the source of the earthquake and sends waves of elastic energy, called seismic waves, throughout the Earth. Earthquakes can be generated by bomb blasts, volcanic eruptions, and sudden slippage along faults. Earthquakes are definitely a geologic hazard for those living in earthquake prone areas, but the seismic waves generated by earthquakes are invaluable for studying the interior of the Earth.

Origin of Earthquakes

Most natural earthquakes are caused by sudden slippage along a fault zone. The elastic rebound theory suggests that if slippage along a fault is hindered such that elastic strain energy builds up in the deforming rocks on either side of the fault, when the slippage does occur, the energy released causes an earthquake. This theory was discovered by making measurements at a number of points across a fault. Prior to an earthquake it was noted that the rocks adjacent to the fault were bending. These bends disappeared after an earthquake suggesting that the energy stored in bending the rocks was suddenly released during the earthquake.

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Earthquakes are a major geological phenomena. Man has been terrified of this phenomena for ages, as little has been known about the causes of earthquakes, but it leaves behind a trail of destruction. There are hundreds of small earthquakes around the world everyday.Some of them are so minor that humans cannot feel them, but seismographs and other sensitive machines can record them. Earthquakes occur when tectonic plates move and rub against each other. Sometimes, due to this movement, they snap and rebound to their original position. This might cause a large earthquakes as the tectonic plates try to settle down. This is known as the Elastic Rebound Theory.

Every year, earthquakes take the lives of thousands of people , and destroy property worth billions. The 2010 Haiti Earthquake killed over 1,50,000 people and destroyed entire cities and villages. Designing Earthquake Resistant Structures is indispensable. It is imperative that structures are designed to resist earthquake forces, in order to reduce the loss of life. The science of Earthquake Engineering and Structural Design has improved tremendously, and thus, today, we can design safe structures which can safely withstand earthquakes of reasonable magnitude.

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Articles by Pravin Kumar

It is not earthquakes that kill people, it is said. In Bhuj, near the epicentre of the recent Gujarat earthquake on January 26, it is reported that nearly 50 per cent of the buildings have been flattened. In Ahmedabad, Surat and Rajkot, high-rise buildings designed by reputed architects and built by good builders have collapsed.

Earthquakes are hazards with a low probability of occurrence, but with major consequences. Hence, our response to them is a case of "being wise after the event". Most constructions in India are non-engineered types, consisting of walls of clay, stone, brick, and the like, built without hazard provisions. Earthquake damage can be mitigated by using earthquake-resistant designs for new buildings and retrofitting existing ones for acceptable levels of risk.

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