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PREFACE:

An earthquake is what happens when two blocks of the earth suddenly slip past one another. The surface where they slip is called the fault or fault plane. The location below the earth's surface where the earthquake starts is called the hypocenter, and the location directly above it on the surface of the earth is called the epicenter.

Sometimes an earthquake has foreshocks. These are smaller earthquakes that happen in the same place as the larger earthquake that follows. Scientists can't tell that an earthquake is a foreshock until the larger earthquake happens. The largest, main earthquake is called the mainshock. Mainshocks always have aftershocks that follow. These are smaller earthquakes that occur afterwards in the same place as the mainshock. Depending on the size of the mainshock, aftershocks can continue for weeks, months, and even years after the mainshock.

Earthquakes are recorded by instruments called seismographs. The recording they make is called a seismogram. The seismograph has a base that sets rmly in the ground, and a heavy weight that hangs free. When an earthquake causes the ground to shake, the base of the seismograph shakes too, but the hanging weight does not. Instead the spring or string that it is hanging from absorbs all the movement. The dierence in position between the shaking part of the seismograph and the motionless part is what is recorded.

Reinforced concrete structures are the most common buildings in urban India, which are subjected to several types of loads during their life time. Seismic analysis is a subset of structural analysis and is the calculation of the response of a building structure to earthquakes; it later became clear that the dynamic properties of the structure aected the loads generated during an earthquake.India has experienced several earthquakes in past few decades, and according to IS 1893:2002 and around 60% (Zone V=60%, Zone IV=18%, Zone III=26%, and Zone II=44%) of its landmass is seismically vulnerable. Especially, in the last two decades, the country has witnessed several moderate earthquakes such as Bihar-Nepal border (M6.4) in 1988, Uttarkashi (M6.6) in 1999 and Kashmir (M7.6) in 2005. The Indian seismic code IS: 1893 indicates that about 60% of country's land area is under threat of moderate to severe earthquake shaking. Even when the earthquake is hazard is highlighted, the lack of knowledge on earthquake-resistant design and construction practices led to considerable damages when exposed to earthquakes that occurred over the last 23 years.

 Building construction is booming in India. More buildings are built in seismic zones of India with current methods of design and construction practices, to make new buildings are earthquake-resistant. Some of the examples are explain in detail.

The 1988 Nepal earthquake occurred in Nepal near the Indian border and aected much of northern Bihar. The magnitude 6.9 earthquake shook the region on August 21, killing at least 709 persons and injuring thousands. The earthquake struck in two installments of 10 seconds and 15 seconds each and left cracks in 50,000 buildings, including Raj Bhava and the old Secretariat Building in Patna, Bihar.

The 1991 Uttarkashi earthquake (also known as the Garhwal earthquake) occurred at 02:53:16 20 October local time with a moment magnitude of 6.8 and a maximum Mercalli intensity of IX (Violent). This thrust event was instrumentally recorded and occurred along the Main Central Thrust in the Uttarkashi and Gharwal regions of the Indian state of Uttarakhand. High intensity shaking resulted in the deaths of at least 768 people and the destruction of thousands of homes.