Download Earthquakes - phillipsearthscience

Shaking of
Earth’s crust
by a release
of energy.
Earthquakes
Cause / Location
• Friction prevents plates from sliding (where plates
meet…fault)  strain builds up  strain overcomes
friction  plates move suddenly releasing ENERGY!!!
• Focus: point of 1st movement
• Epicenter: point on Earth’s surface directly above
focus.
Rows of lettuce in CA in 1979. Displaced by an
earthquake.
Earthquake (Seismic) Waves
• P waves:
–
–
–
–
–
Primary waves (Get to you 1st)
Fastest (about 6km/sec)
Compressional waves
Squeeze and stretch rock
Can travel though solid and liquid material.
• S waves:
– Secondary waves
– About 3km/sec
– Material moves at right angles to the direction in which the
wave is traveling
– Can travel through solid material, but not through liquids.
• Surface Waves:
– P and S waves produce surface waves
– About 1.5 km/sec
– 2 types:
• Love waves: material moves from side to side
• Rayleigh wave: material moves in elliptical patterns.
Seismograph
• Detects and records
waves produced by
earthquakes
– Can pick up activity
thousands of miles away
• Use data to locate
earthquakes’ epicenters
and to measure their
magnitudes
• About 10,000 stations
around the world
Seismogram
Summarize!
• Foci and epicenters
• 4 wave types and notable characteristics
• P- and S-wave shadow zones (where and
why)
• Seismographs and seismograms