Earthquake Focus The point in the Earth’s interior where the is energy release occurs.
Primary Waves: Waves that move through Earth by causing particles in rocks to move back and forth in the same direction the wave is traveling.
Secondary Waves Move through Earth by causing particles in rocks to move at right angles to the direction of the wave.
Surface Waves Move by giving particles an elliptical motion, as well as a back-and-forth swaying motion.
Epicenter The point on Earth’s surface directly above an earthquake’s focus.
Locating an Epicenter 1. S-P Interval: Take the difference in arrival time of the primary and secondary waves. 2. Find the distance from the seismic station and the epicenter. For 3 stations. 3. Plot the distances as radii on three circles. Where they meet is where the epicenter is located.