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Chapter 19Chapter 19Pg. 526Pg. 526
Earthquakes
VocabularyVocabulary• Deformation- The bending,
tilting, and breaking of Earth’s crust.
• Stress- The total force acting on crustal rocks per unit of area.
• Strain- The deformation of material in response to stress.
• Fault- A fracture along which crust move.
Movement- Pulled away from each other
Boundary- Divergent
Stress- Tension
Fault- Normal
Normal faults commonly form at divergent boundaries, where the crust is being pulled apart by tension.
Movement- Push together
Boundary- Convergent
Stress- Compression
Fault- Reverse
Reverse faults normally form at convergent plate boundaries, where the crust is being pushed together by compression.
Movement- Moves side-by-side
Boundary- Transform
Stress- Shear
Fault- Strike-Slip
Strike-slip faults normally occur along transform plate boundaries, where the crust is moving side-by-side by shear stress.
How and Where Earthquake Happen
oEarthquakes occur when Earthquakes occur when rocks under stress suddenly rocks under stress suddenly shift along a fault.shift along a fault.
oVibration of Earth caused by Vibration of Earth caused by the release of energy by the the release of energy by the movement of the fault or movement of the fault or plate. plate.
oAssociated with movements Associated with movements along faults and plate along faults and plate boundariesboundaries
VocabularyFocus- The exact point underground where the energy is released. Where the earthquake starts. Epicenter- The point of Earth’s surface directly above the focus.
Primary (P) Wave• Primary waves are a type of body
wave (travel inside Earth).
• Primary waves are the fastest waves and are the first to reach seismic stations.
• Push-pull motion (compressional waves)
• Travels through solids, liquids, & gases
Secondary (S) Wave• Secondary waves are a type of body
wave (travel inside Earth).
• Secondary waves are the 2nd fastest waves and are second to reach seismic stations.
• “side-to-side” motion (sheer waves)
• travels only through solids
Love and Rayleigh Waves• Love and Rayleigh waves are a type of
surface wave (travel on Earth’s surface).• Very destructive seismic waves.• Slow moving seismic waves• Love waves are surface waves that
cause rock to move side-to-side and perpendicular to the direction of the wave.• Rayleigh waves are surface waves
cause the ground to move with an elliptical, rolling motion.