The seismic waves can be divided into primary, secondary and surface waves. Primary Seismic Waves reach first to the surface of the earth after the energy is emitted in the earth’s interior.They travel in radial direction. These waves can travel through allthe three states – liquid, solid and gaseous.The buildings on the earth’s surface moveback and forth because of Primary Seismicwaves. Secondary waves reach after the Primary Seismic Waves. They scatter in all directions from the focus.These waves can travel only through the solidMedium.The buildings on the earth’s surface move upand down because of these waves. After the main P and S waves the surface waves reach the epicenter and travel in the direction of the circumference of the earth along the crust.
