Study Guide (Part 5)
Earthquakes
Key Vocabulary Terms for Part 5:
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Aftershock – A smaller earthquake that follows a larger earthquake.
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Body Waves – Waves of energy that travel from the focus of an earthquake through the
material of Earth’s body; P waves and S waves are two types of body waves.

Earthquake – The shaking of earth’s crust caused by a release of energy.
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Elastic-rebound Theory – The theory that earthquakes occur when the stress building up
between two lithospheric plates overcomes the force of friction, causing the plates to
suddenly move, release energy, and then snap back to their former shapes.
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Epicenter – The point on Earth’s surface directly above the focus of an earthquake.
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Fault – A break in the lithosphere along which movement has occurred.
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Focus – _The point at which the first movement occurs during an earthquake
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Liquefaction – A temporary state in which loose soil and rock materials take on the property
of liquid, often as a result of severe ground-shaking.

Magnitude – The measure of the amount of energy released in an earthquake

Mohorovicic Discontinuity (Moho)– The boundary between Earth’s crust and mantle

P Waves – Body waves that squeeze and stretch rock materials as they pass through Earth;
also known as compressional waves or primary waves.

S Waves – Body waves that cause particles of rock material to move at right angles to the
direction in which the waves are traveling; also known as shear waves or secondary waves.

Seismic Gap – An area along a seismically active fault where no earthquake activity has
occurred over a long period of time
Study Guide (Part 5)

Seismograph – An instrument that detects and records waves produced by earthquakes

Shadow Zone – The wide area around Earth on the side opposite an earthquake’s focus
where neither P waves or S waves are received.

Surface Waves – Earthquake waves that travel along Earth’s surface; Love waves and
Rayleigh waves are two types of surface waves.

Tsunami – A large ocean wave that results from an underwater earthquake, landslide, or
volcanic eruption.
Notes for Part 5:

What is the cause of most major earthquakes (pg. 214)? The strain that builds up along
faults at or near boundaries between lithospheric plates.

What prevents the plates from moving causing strain and tension to build up (pg. 214)?
Friction

What kind of seismic body wave can travel through liquids and solids (pg. 215)? P waves
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What kind of seismic body wave can travel only through solids (pg. 215)? S waves

What is the difference between surface waves and body waves (pg. 215-216)? Body waves
travel through the Earth from the earthquake’s focus while surface waves travel along
the Earth’s surface. P waves & S waves produce surface waves once they reach the
surface.

What type of seismic waves travel slower than P waves or S waves (pg. 216)? Surface
waves

What kind of damage can occur after an earthquake (pg. 222)? Aftershocks, liquefaction
(which leads to foundation failure), fires, and tsunamis
Study Guide (Part 5)

What was the main difference to the destruction of buildings in San Francisco after an
earthquake in 1906 and 1989 (pg. 222)? In 1906 San Francisco could not control the fires
that raged out of control, and in 1989 the buildings were built to better handle the
earthquakes so the only ones affected were ones on poor foundations where liquefaction
happened.

What made the situation worse in San Francisco after the earthquake of 1906 (pg. 223)? The
gas and water lines were severed during the earthquake which prevented the
firefighters from putting out the fires and 3,000 buildings were destroyed in the process.

What is the average speed of a tsunami at an ocean depth of 4500 meters (pg. 223)? 750
kilometers per hour (kph)

How did scientist use earthquakes to figure out the structure of Earth’s interior (pg.228)?
They studied the velocities of the P waves and S waves and saw that they travelled at
different speeds depending on the density of the material which allowed scientists to
determine the different layers of the Earth’s interior. They also knew that P waves and
S waves can’t travel through the same material (liquids and solids) so that also helped
the scientists identified the composition of Earth’s interior, and more specifically the
core.