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## PowerPoint Slideshow about ' EARTHQUAKES' - sandro

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### EARTHQUAKES

Shaking Crust

EARTHQUAKES

- Vibrations produced by breaking of lithosphere (crust & upper mantle)
- Elastic limit = amount that rocks can stretch and bend
- When surpassed rocks break & move
- Seismic waves (vibrations) sent out in all directions

Fault

- Surface along which rocks move

3 Types of Faults

- Normal Thrust/Reverse Slip
Fault Fault Fault

Focus vs. Epicenter

- FOCUS – point below the surface where rocks actually break
- EPICENTER – point on surface directly above the focus

Primary Seismic Waves

- P wave
- Longitudinal wave – particles move parallel to wave direction
- Fastest
- Least destructive

Secondary Seismic Waves

- S wave
- Transverse wave – particles move at right angles to wave direction
- Slower than P waves
- More destructive than P waves

Surface Waves

- L wave
- Particles move in ellipses compared to wave direction
- Slowest
- Most destructive

LAG TIME

- LAG TIME = difference between first S wave and first P wave arrival at a seismic station
- Longer lag time = further from the epicenter

Time-Travel Graph

- Compares distance from epicenter to lag time

Seismograph Station-Locating an Epicenter

- Triangulation-information from at least 3 seismic stations
- Seismograph measures how much the surface of the earth moves
- Draw 3 circles
- Intersection = Epicenter

Richter Scale- Measures the Magnitude

- Measures amount of energy released, magnitude
- OBJECTIVE scale
- NOT influenced by other factors
- Used to compare earthquakes
- Increase of “1” = 10 times more energy released

Mercalli Scale

- Measures amount of damage done to man-made structures
- SUBJECTIVE scale
- Influenced by many factors (height of buildings, age, how built, etc. . .)
- Used to determine amount of $$$ for aid

San Andreas Fault- edge of the Pacific plate is slipping past the North American plate

San Andreas Earthquake

http://earthquake.usgs.gov/regional/nca/1906/18april/index.php

San Andreas Earthquake

http://earthquake.usgs.gov/regional/nca/1906/18april/index.php

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