Seismic waves are waves of energy that travel through the Earth's layers as a result of earthquakes, volcanic eruptions, and other events. There are three main types of seismic waves: P-waves, which are pressure waves that travel fastest; S-waves, which are slower shear waves; and surface waves, which travel along the Earth's surface and include Rayleigh and Love waves. Seismologists can use measurements of seismic wave arrival times and properties to learn about the Earth's deep interior structure and locate earthquake epicenters.