Seismic waves travel a curving path through the earth due to changes in composition, pressure, temperature within the layers of the Earth. If there were no changes with depth, seismic waves would travel a straight path to the other side of the Earth. But wave arrivals to distant seismic stations have taught us that there are layers. Seismic waves through the Earth follow the same laws of refraction and reflection as any other wave at interfaces. When they encounter boundaries between different media, the wave will react according to Snell’s law, and the angle of refraction across the boundary will depend on the velocity of the second media relative to the first.
Narrated by Dr. Wendy Bohon, Informal Education Specialist, IRIS
Animation by Jenda Johnson, Earth Sciences Animated
