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.