Earthquake!! The P wave propagates at ~6 km/sec in rock with particle motions that are parallel to the direction of propagation. The S wave is slower at 4 km/sec and propagates with particle motions that are perpendicular to the direction of propagation. When we record these waves, the gap between the P wave and the S wave provides information about how far away the earthquake occurred from the seismograph.
CLOSED CAPTIONING: A .srt file is included with the download. Use an appropriate media player to utilize captioning.
