Transcript What are seismic waves?

Warm-up- 8 minutes
Which type of boundary creates new
lithosphere/oceanic crust?
2) Which type of boundary is associated with
mountains and volcanoes?
3) This boundary neither creates nor destroys
plates.
4) Stephen is visiting the mountains in
Colorado. What type of tectonic plate
boundary is Stephen near?
Answer in complete sentences.
1)
What is an Earthquake?
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Vibration of earth caused by rapid
release of energy.
Transform plate boundaries produce
earthquakes
What is a focus?
The point beneath the
Earth’s surface where
rock under stress breaks
to cause an earthquake.
What is an
epicenter?
The point on the
surface directly
above the focus.
The farther the distance
between the focus and the
epicenter, the weaker the
earthquake. Therefore,
the closer the focus is to
the surface, the stronger
the earthquake.
Distance from Focus to Epicenter
What is a fault?
It is the break in the crust
where the earthquake began,
between two blocks of rock
that have moved past each
other.
Question A
What is the primary cause of
earthquake activity?
1. Lowering of aquifer levels
2. Mining activity in the 19th century
3. Interaction of tides with the coast
4. Plates grinding past each other
along fault lines
Question B
The area in which an earthquake
starts, or where rocks begin to
break, is the
1. Breaks in the Earth’s lithosphere
2. Focus
3. Epicenter
4. Hot spots
3 Types of Faults
Normal
Reverse
Strike-slip
When the hanging
wall drops down.
When hanging
wall moves up.
Walls move
sideways
Creates forces that Creates
pull the sides apart compressional
forces.
Horizontal
forces
12
Question C
A reverse fault occurs when
1. The land is thrust UP
2. The land is dropped DOWN
3. The land slides past another piece of
land
4. There is a convergent boundary in
play
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What are seismic
waves?
Seismic waves are the
waves (vibrations)
caused by earthquakes
During an earthquake,
vibrations called seismic
wave move out from the focus
in all directions similar to the
ripples created by a pebble in
a pond.
Seismic waves carry the energy
of an earthquake away from the
focus, through the Earth’s
interior, and across the surface.
What are the three types
of seismic waves?
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Primary waves
(P waves)
Secondary Waves
(S waves)
Surface waves (L waves)
Describe a P wave.
Travel the fastest
 Travel solids, liquids, and gases
 Move through the Earth at
different speeds, depending on
the density
 Called “push-pull” waves
(compress and expand the
ground like an accordion)

Describe an S wave.
Arrive at a given point after the
P waves
 Travel only through solids
 Move through solids at different
speeds depending on the density
 Cause rock particles to move
from side to side & up and down

Describe a L wave.
Slowest of the seismic
waves
 Move along the Earth’s
surface like waves travel in
the ocean
 Cause most of the damage
during an earthquake
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When the P & S
waves reach the
surface, they move
more slowly creating
the most severe
ground movements.
Question D
In order from most destructive to least
destructive, name the different
waves that are associated with
earthquakes
1. Surface (L), s-wave, p-wave
2. P-wave, s-wave, surface (L)
3. Surface wave, p-wave, s-wave
4. S-wave, p-wave, surface (L)
Guided Practice- 15 minutes
Using your notes, you will make a foldable
of fault lines and seismic waves.
1. One the front describe AND draw each
type of fault line.
2. On the back, describe AND draw each
type of seismic wave.
I will walk around and record participation
grades
3 Types of Faults
Normal
Reverse
Strike-slip
When the hanging
wall drops down.
When hanging
wall moves up.
Walls move
sideways
Creates forces that Creates
pull the sides apart compressional
forces.
Horizontal
forces
Seismographs are used by
scientist to detect, measure &
record the vibrations of
seismic waves.
An earthquake’s magnitude is a
measurement of its strength based
on seismic waves and movement
along faults.
https://www.youtube.com/watch?v=
Gbd1FcuLJLQ
What are 3
rating scales
used to
measure an
earthquake?
Mercalli scale –
This scale rates
earthquakes by describing
their effects on people,
buildings, and the land
surface in a given
location.
Richter scale
This scale rates
earthquakes according to
the size of seismic waves
as measured by the
seismograph.
Moment Magnitude
scale
This scale rates earthquakes by
estimating the total energy
they release. The moment
magnitude scale can be used
to measure earthquakes of
all sizes, near or far!
How do scientists
determine the
location of an
earthquake’s
epicenter?
When an earthquake
strikes, P waves are the
first to arrive at a
seismograph followed by
the S waves.
 The farther away the
epicenter is, the greater
the difference between
the two arrival times.
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This difference in time tells
scientists how far the
seismograph is from the
epicenter. This information
is then used to plot a circle
on a map.
The circle shows the
distance from one
seismograph station to all
points where the epicenter
could be located.
.
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To determine the exact
location of the epicenter, at
least THREE stations need to
find their distance from the
epicenter and draw a circle
on a map
The single point
where the 3 circles
intersect is the
location of the
earthquake’s
epicenter.
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In the Additional Notes section of
your Guided Notes, write down a
brief COMPLETE SENTENCE
summary of today’s lesson (3-5
sentences).
What are the main points that
you would need to teach to an
absent student?
Pen Pal Letter- 25 min
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1.
2.
3.
4.
5.
6.
Write a letter to a friend (real or
imaginary) about what earthquakes are
and how they are formed. In your letter,
you must include the words below. Be
sure to circle these words so that I can
identify them.
Earthquakes (define them)
Transform boundaries
Focus
Epicenter
Fault lines (describe all 3 types and describe
each)
Seismic waves (identify and describe all 3)
Earthquake Pen Pal Letter, By Your name
Dear Liz,
I learned about Earthquakes in Earth Science class
today. Earthquakes are vibrations on the Earth’s
surface caused by rapid release of energy. They are
formed at transform boundaries.
Etc.
Sincerely,
Dr. Cao
Exit Ticket
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Draw the three types of faults
(normal, reverse, and strikeslip). What happens at each
fault?