When an earthquake occurs, seismic waves propagate through the Earth and across its surface. You can watch this happen in speeded-up time.
The three-dimensional Earth view, in the lower left, illustrates how P waves (red), S waves (blue), and surface waves (yellow) spread across Earth's surface away from the earthquake's epicenter. They move outward like the circular ripples on a pond created by a tossed stone.
The cross-sectional Earth view, in the lower right, shows the P and S waves that move through the planet. When they encounter internal boundaries in the Earth, such as that between the lower mantle and outer core, these waves are partially reflected back toward the surface and partially refracted to pass through the boundary. Note that S waves, which propagate by shearing, can not travel through the liquid outer core because liquids can't be sheared.
The speed indicated by the slider is relative to real time. For example, a speed of 60 indicates that a second of motion on the screen represents a minute in the real world.
Each of the three windows on the screen has its own information button.
