Download What are Seismic Waves?

What are Seismic Waves?
Types of Waves
• Compression wave (longitudinal)
• Transverse Wave
• Seismic Wave
– Body Waves
• Primary or p-wave
–Compression wave
• Secondary or s-wave
–Transverse wave
– Surface
• Love wave
• Rayleigh wave
Seismic Wave
• Seismic waves are the waves of energy
caused by the sudden breaking of rock
within the earth or an explosion. They are
the energy that travels through the earth
and is recorded on seismographs.
• There are several different kinds of
seismic waves, and they all move in
different ways. The two main types of
waves are
– body waves
– surface waves
How Seismographs Work
The pendulum remains
fixed as the ground
moves beneath it.
Typical Seismogram
Body Waves
• P Waves (compression wave)
• The first kind of body wave is the P wave or
primary wave. This is the fastest kind of seismic
wave. The P wave can move through solid rock and
fluids, like water or the liquid layers of the earth.
It pushes and pulls the rock it moves through just
like sound waves push and pull the air.
Primary Waves (P Waves)
• A type of seismic wave that compresses
and expands the ground
• The first wave to arrive at an
earthquake
Stop and Think
• Have you ever heard a big clap of
thunder and heard the windows rattle at
the same time?
• The windows rattle because the sound
waves were pushing and pulling on the
window glass much like P waves push and
pull on rock. Sometimes animals can hear
the P waves of an earthquake. Usually
we only feel the bump and rattle of
these waves.
Body Waves
• S wave (transverse wave)
• The second type of body wave is the S wave or
secondary wave, which is the second wave you
feel in an earthquake. An S wave is slower than a
P wave and can only move through solid rock. This
wave moves rock up and down, or side-to-side.
Secondary Waves (S Waves)
• A type of seismic wave that moves the
ground up and down or side to side
Comparing Seismic Waves
Surface Waves
• Move along the Earth’s surface
• Produces motion in the upper crust
– Motion can be up and down
– Motion can be around
– Motion can be back and forth
• Travel more slowly than S and P waves
• More destructive
• Types:
– Love
– Rayleigh
Surface Waves
• Love Waves
• The first kind of surface wave is called a Love
wave, named after A.E.H. Love, a British
mathematician who worked out the mathematical
model for this kind of wave in 1911. It's the
fastest surface wave and moves the ground from
side-to-side.
Surface Waves
• Rayleigh Waves
• The other kind of surface wave is the Rayleigh wave,
named for John William Strutt, Lord Rayleigh, who
mathematically predicted the existence of this kind of
wave in 1885. A Rayleigh wave rolls along the ground
just like a wave rolls across a lake or an ocean. Because
it rolls, it moves the ground up and down, and side-toside in the same direction that the wave is moving.
Most of the shaking felt from an earthquake is due to
the Rayleigh wave, which can be much larger than the
other waves.
Earthquakes
What is an earthquake?
• Used to describe both sudden slip on a
fault, and the resulting ground shaking
and radiated seismic energy caused by
the slip
• Caused by volcanic or magmatic activity,
• Caused by other sudden stress changes
in the earth.
What causes earthquakes?
• Tectonic plates move past each other
causing stress. Stress causes the rock
to deform
Focus –
point inside the Earth where an
earthquake begins
Epicenter – point on Earth’s surface above
focus
How do scientists calculate how far a location
is from the epicenter of an earthquake?
• Scientists calculate the difference
between arrival times of the P waves and
S waves
• The further away an earthquake is, the
greater the time between the arrival of
the P waves and the S waves
Locating Earthquakes
Locating Earthquakes
Locating Earthquakes
How are Earthquakes Measured?
Richter Scale
How are Earthquakes Measured?
Mercalli Intensity Scale
Click Link for Interactive Demo
http://elearning.niu.edu/simulations/images/S_portfolio/Mercalli/Mercalli_Scale.swf
Earthquake Waves & Earth’s Interior
Seismic
Waves
in the
Earth
Tsunamis
Formation of a Tsunami
Tsunami Warning System
Now it is your turn!!
• Click on the following link:
•
http://www.sciencecourseware.com/eec/Earthquake/EpicenterMagnitude/
• Now start activity using handout at end of notes.
• You must use the following code
– For 3rd period use
• 2113714
– For 4th period use
• 2113861
- For 6th period use
- 2113947
Assignment due by Tues March 26 by end
of class!