Seismic Wave Behavior and Properties

The video explains how seismic waves would travel in straight paths if the Earth had no changes with depth. However, due to variations in composition, density, and temperature, seismic rays refract as velocity generally increases with depth. The video zooms into the crust to observe wave behavior at boundaries of higher velocity, tracking two paths from an earthquake. The direct path travels through the slowest layer, while the outer path refracts at increased velocity boundaries, eventually sending a head wave to the surface. These waves follow Snell's law, with some reaching Station X before the direct wave due to significant velocity increases.

What would happen to seismic waves if the Earth had no changes with depth?

• They would travel in zigzag paths.

• They would stop moving.

• They would travel in straight paths.

• They would travel in curved paths.

What causes seismic rays to refract as they travel through the Earth?

• Changes in the Earth's magnetic field.

• Changes in the Earth's composition, density, and temperature.

• The rotation of the Earth.

• The presence of water in the Earth's crust.

What happens to seismic waves when they cross into boundaries of higher velocity?

• They refract.

• They slow down.

• They travel in straight lines.

• They stop moving.

What is the critical angle in the context of seismic waves?

• The angle at which waves travel in straight lines.

• The angle at which waves start sending a head wave to the surface.

• The angle at which waves stop moving.

• The angle at which waves reflect back to the source.

Why do some critically refracted waves reach the surface faster than direct waves?

• Because they travel through a vacuum.

• Because the velocity increases were great enough to overcome the slower direct path.

• Because they travel in a straight line.

• Because they are unaffected by the Earth's composition.