Earthquakes Seismic Waves General Info Seismic waves are

Earthquakes!

Seismic Waves General Info Ø Seismic waves are the energy released when rocks break along faults. Ø Focus = the point within the Earth’s Interior at which this energy is first released. Ø Seismic waves are produced and travel outward from the earthquake focus. Ø Are Seismic Waves Compressional or Transverse Waves? – Why? ?

Epicenter EQ Epicenter = the point on the Earth’s surface directly above the earthquake’s focus. The speeds of seismic waves allows us to determine how far away earthquake epicenter is from a seismic station. Measured with Seismograph.

“Body” Waves 1) P-waves (Primary Waves) 1) Fastest Seismic Wave Cause particles in rocks to move back & forth in same direction. Ex: Stretched Spring, Compressional / Sound Wave. 2) S-waves (Secondary Waves) Cause particles in rocks to move at right angles to the direction of the wave travel. Ex: Ocean Wave, Transverse Wave.

Surface Waves Move rock particles in a rolling, side-to-side, swaying motion. Most damaging type of seismic waves.

Measuring EQ’s Ø Richter Scale Used to measure the strength of an earthquake. l Based on the height of the lines on the seismograph. l Scale has no upper limit, but 9. 5 is estimated maximum. l

Measuring EQ’s Ø Mercalli Intensity Scale Used to measure the intensity of an earthquake based on the amount of damage caused by the earthquake. l Scale has 12 levels. l