• Seismic waves are waves that travel through
Earth’s interior
• Much of what we know about Earth comes from
the study of seismic waves and how they travel
through different material.
• Studying these waves helps us understand
earthquakes and how to build things that
withstand the different types of waves
associated with earthquakes
There are four types of Seismic Waves
2 Body Waves• They are called body
waves because they
travel through the Earth.
• These are P & S waves.
P = compressional
S = secondary or shear
2 Surface Waves• They are called surface
waves because they
travel primarily on the
surface.
• These are Love waves
and Rayleigh waves.
• Body waves may also be
used in identifying the
epicenter of an
earthquake
• P waves are the faster of the two waves.
• They can travel through solid rock and liquid, as
well as air.
• As a P wave travels through a medium
(material), it causes particles to move in the
same direction as the wave energy is traveling.
• As the waves pass through the medium, they
cause compressions (shortening) and dilations
(expansions).
• S waves are slower than P waves.
• S waves ONLY move through solid
rock.
• As S waves pass through a medium,
particles move perpendicular to the
direction of the wave’s energy path.
Two types of Surface Waves
• Love waves are names after the mathematician
A.E.H. Love, who devised the model of this wave
in 1911.
• Love waves are the faster waves of the 2 types
of surface waves.
• As the Love waves travel across the surface of
the Earth, the particles move from side to side,
perpendicular to the path od the wave’s
energy.
• Rayleigh waves are also called “ground rolls” in
earthquakes and are similar to water waves.
• A Rayleigh wave rolls along the ground just like a
wave rolls across a lake or ocean.
• Because it rolls, it moves the ground up and down, and
side to side in the same direction the wave is moving.
• Most of the shaking from earthquakes is due to
Rayleigh waves, which can be much larger than the
other waves
• Rayleigh waves are named after Lord Rayleigh who
used math to predict the existence of this wave.
Wave Fronts and Rays