What type of surface wave causes both vertical and horizontal ground movement via an elliptical motion?

The correct answer is Rayleigh Waves, which are a type of surface wave generated by seismic events. These waves move in an elliptical motion, resulting in both vertical and horizontal displacements of the ground. This characteristic makes them particularly effective at causing damage during an earthquake, as they create rolling motions that can lead to significant shaking.

Rayleigh Waves are named after Lord Rayleigh, who mathematically described them. They travel along the surface of the Earth and are one of the slowest seismic waves but often cause the most destruction due to their complex motion, which affects buildings and structures.

While Love Waves are also surface waves, they primarily cause horizontal ground movement without the vertical component that Rayleigh Waves exhibit. Surface Waves is a broader category that includes both types of waves but does not specifically describe the elliptical motion. P Waves, or primary waves, are compressional waves that travel through the body of the Earth, moving particles back and forth in the direction of wave propagation and do not exhibit the surface characteristics of Rayleigh Waves.