Seismic Waves

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Earthquake Vocabulary

By looking at this picture, try to come up with

a definition of “epicenter” and “focus”

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Earthquake Vocabulary

• Focus—location of EQ inside Earth

• Epicenter—location directly above focus on

Earth’s surface

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How do we feel earthquakes?

If earthquakes start at the focus deep inside

earth, how do we feel it on the surface?

How Earthquakes Travel

• Seismic waves—vibrations that travel

through Earth caused by EQs

Types of Seismic Waves

Primary Wave(P-wave)

Secondary Wave(S-wave)

Surface Wave

3 types of seismic wavesDirection of earthquake

Types of Seismic WavesPrimary Wave

(P-wave)

Secondary Wave(S-wave)

Surface Wave

• Travels through

ground

• Travels through

ground

• Travels only on

Earth’s surface

• Fastest waves • Medium speed waves • Slowest waves

Types of Seismic WavesPrimary Wave

(P-wave)

Secondary Wave(S-wave)

Surface Wave

• Travels through

ground

• Travels through

ground

• Travels only on

Earth’s surface

• Fastest waves • Medium speed waves • Slowest waves

• Can travel through

solid and liquid

• Only travel through

solids

Types of Seismic WavesPrimary Wave

(P-wave)

Secondary Wave(S-wave)

Surface Wave

• Travels through

ground

• Travels through

ground

• Travels only on

Earth’s surface

• Fastest waves • Medium speed waves • Slowest waves

• Can travel through

solid and liquid

• Only travel through

solids

• Rock particles move

in the same direction

as EQ

• Rock particles move

perpendicular to

direction of EQ

Perpendicular (opposite direction) to movement of EQ

Same direction as EQ

Types of Seismic WavesPrimary Wave

(P-wave)

Secondary Wave(S-wave)

Surface Wave

• Travels through

ground

• Travels through

ground

• Travels only on

Earth’s surface

• Fastest waves • Medium speed waves • Slowest waves

• Can travel through

solid and liquid

• Only travel through

solids

• Rock particles move

in the same direction

as EQ

• Rock particles move

perpendicular to

direction of EQ

• Rolling motion

Types of Seismic WavesPrimary Wave

(P-wave)

Secondary Wave(S-wave)

Surface Wave

• Travels through

ground

• Travels through

ground

• Travels only on

Earth’s surface

• Fastest waves • Medium speed waves • Slowest waves

• Can travel through

solid and liquid

• Only travel through

solids

• Rock particles move

in the same direction

as EQ

• Rock particles move

perpendicular to

direction of EQ

• Rolling motion

Direction of EQ Direction of EQ Direction of EQ