The dynamic response of the building to earthquake ground motion is the most important cause of damages to the building that are induced by earthquake. Failure of the ground and soil beneath building is another major cause of damages. Nevertheless, contrary to the popular belief, buildings rarely get damaged on account of fault displacement beneath a building.
Mostly earthquakes take place due to rapid movement along the fault planes inside the crust of the earth.
Due to this sudden movement of the fault lines, a great deal of energy is released, which then propagates through the earth in the form of seismic waves. The seismic waves cover a great distance before they lose most of their energy. In figure given below the basic features of all forms of wave motion, not only of seismic waves.
When at a point of time after their origin, the seismic waves reach the surface of the earth and set it in motion, it is known as earthquake ground motion. In the event of this earthquake ground motion occurring under a building and it is quite strong, it sets the building in motion, beginning with the foundation of the building and then transferring the motion, throughout the building in a quite complicated manner. These motions consequently generate forces that can make damages.