Seismic Waves 3 Types Cornell Notes page 123

Seismic Waves- 3 Types Cornell Notes page 123

Surface Waves • Travel slowly along Earth’s surface • usually most destructive

Body Waves • Travel more quickly through Earth’s layers • 2 types

Body waves 2 types: P Waves • “Primary” wave • Fastest wave • Longitudinal compression waves • Travel through both solids and liquids

Body Waves- • “Secondary” waves 2 Types: • Slower than P waves, but faster S Waves than surface waves • Travel side to side (like a snake) • Can only travel through solids

Assignment: Draw P and S waves S Waves (secondary waves) • SIDE to SIDE motion • Slower moving than P waves • Travel only through solids P Waves (primary waves) Straight ahead motion Faster than S waves Travel through all parts of Earth

Determining distance from seismograph to epicenter • P waves and S waves travel at different speeds. • Time between when P wave arrives and when S wave arrives can be used to determine how far away the epicenter is from that station.

Using Triangulation • The seismograph can tell us how far away the EQ is, but not in which direction. • Must use at least 2 other stations to locate the epicenter.

Using Triangulation 1. Determine distance from station to epicenter. 2. Draw circle around station with radius = to distance. 3. Do the same for at least 2 other stations. 4. Place where all 3 circles meet is the epicenter.

Depth of Focus • Shallow focuses (less than 70 km deep) are more destructive than deep focuses (over 300 km deep).