Earthquakes Section 17.2

Earthquakes Shaking of the Earth’s crust caused by a release of energy Build-up of stress Stress overcomes friction Plates slip (EQ) Land snaps back into original shape

3. Earthquakes Focus – point UNDERGROUND where movement starts Epicenter – point ON THE SURFACE directly above focus

3. Earthquakes Seismic Waves: Body Waves P-Waves aka “Primary Waves” Compressional wave movement Travel through solids, liquids, and gasses

3. Earthquakes Seismic Waves: Body Waves S-Waves aka “Secondary Waves” Arrive second, slower than p-waves Side-to-side wave movement Travel through solids ONLY

3. Earthquakes Seismic Waves: Surface Waves L-Waves aka “Land Waves” or “Surface Waves” Last waves to occur Cause most damage Rayleigh Waves or Love Waves

3. Earthquakes P S Body Wave Mantle Outer Core (liquid) Inner Core (solid) P Speed up, refract Slow down Speed up S STOP

3. Earthquakes

3. Earthquakes

Collapse Because Lack of Shear Walls San Fernando, Ca 1971 Loma Prieta, Ca 1986 San Francisco