Hyperstudio Questions 1. When an earthquake occurs the energy produced from the movement of the plates of the Earth radiates out from the focus in the form of seismic waves. The Richter scale is a measure of the strength and length of time that earthquake lasts. Compression waves are the fastest waves produced from an earthquake. They hit the surface with a pounding or jackhammer motion.
Shear waves are about half the speed of P waves.
They hit the surface with a rolling, up and down motion. Surface waves are the last waves to strike the surface and are confined to the upper layers of the Earth. The are the slowest waves and cause the most damage. There are two kinds of surface waves Love and Rayleigh waves. The pyroclastic flow of very hot steam, gas, and ash.