Which seismic wave is characterized by shaking that is perpendicular to the direction of the wave?

The S wave, or secondary wave, is distinguished by its unique movement, which involves shaking that is perpendicular to the direction of wave propagation. This characteristic means that as the S wave travels through the Earth, it causes the ground to move up and down or side to side at a right angle relative to the wave's path.

S waves are a type of shear wave, and they can only travel through solids, which is an important aspect of understanding the Earth's internal structure. Their movement is responsible for the significant shaking experienced during an earthquake, typically coming after the P waves but being more damaging due to their strong lateral motion.

In contrast, the P wave, or primary wave, moves in the same direction as it propagates, compressing and expanding the material it travels through. The Richter wave does not exist as a specific type of wave but rather refers to a scale to measure the intensity of seismic waves. Surface waves have characteristics similar to S waves in their shaking, but they travel along the Earth’s surface and involve both vertical and horizontal movements, making them a different category altogether.