Earthquake

An earthquake is a series of vibrations on the earth's surface caused by the generation of seismic waves due to sudden rupture within the earth during release of accumulated strain energy. Most recent seismic codes include response modification factors in the definition of the equivalent lateral forces that are used for the design of earthquake resistant buildings. The crust of the earth when it is subject to tectonic forces, bends slightly. But, because the crust is rigid, when the stress or pressure exceeds the strength of the rocks, the crust breaks and snaps into a new position. The effects of earthquakes vary. This is a result of a variety of factors such as the strength of the earthquake, the level of population in an area and the level of economic development of the area struck. Earthquakes cause thousands of deaths worldwide every year, and systematic study of the causes of these deaths can lead to their prevention. Few studies have examined how multiple types of risk factors are related to physical injury during an earthquake.