Transcript Chapter 19 - Earthquakes

Chapter 19 - Earthquakes
19.1- Forces within Earth
1/5/16, Tuesday To-Do
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Bellringer: What causes Earthquakes?
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Get a copy of the Learning Target
Inventory off of the front stool. Rate
yourself on each learning target.
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If you have not taken your semester 1
exam yet, I’ll be giving it to you tomorrow.
1/5/16 Tuesday
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Often, you may hear people say that the
animals and fish seemed to sense there is
an earthquake coming. Why/how do you
think that may be possible?
To-Do 1/4/16, Monday
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Bellringer: What would you do during an
earthquake?
Bellringer: 1/6/16 Wednesday
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*Define what you think Stress and Strain is
as they apply to rocks.
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Get a copy of the guided notes off of the
front stool.
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We’ll Finish reviewing earthquake safety
and take notes on stress and strain.
Earthquakes:
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Earthquake = vibrations caused by
movement in crust
Are the result of movement of crust
produced by Plate tectonics
Stress = total force acting on crustal rocks
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Builds up overtime
Overcomes strength of rocks and causes
movement along fractures in rock
http://earthquake.usgs.gov/learning/kids/sciencefair.php
Stress
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Three types
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Compression – decrease volume of material
Tension – pulls material apart
Shear – causes material to twist
Strain = deformation of material in a
response to stress
Deformation
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Elastic – when a material is compressed,
bent, or stretched
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at low stress
Material can return to “normal” when stress is
zero
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Example: Pulling on a rubber band
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Deformation
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Plastic – stress builds up past elastic limit
Permanent deformation – stays changed
even when stress is zero
Point of Rupture = failure
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Example: Pulling rubber band until it breaks
Deformation
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Most materials exhibit varying degrees of
plastic and elastic deformation
http://www.uwsp.edu/geo/faculty/ritter/images/lithosphere/Earth_Structure/plastic_deformation.jpg
Bellringer:
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Compare and contrast the movements of
each of the three types of faults. Page 531
in your book.
Faults notes:
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Any fracture or system of fractures along
which Earth moves
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Happens along weak regions
Fault plane = surface along which
movement takes place
Fault Animation:
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Fault Motion:
http://www.iris.edu/gifs/animations/faults.ht
m
Examine animations of fault motion:
http://www.classzone.com/books/earth_sci
ence/terc/content/visualizations/es1103/es
1103page01.cfm
What kind of fault is it?
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Fence offset produced by 1906 San Francisco
earthquake Right-Lateral Strike-Slip Faults The fence
was offset 2.6 m by the magnitude 8.2 earthquake of
April 18, 1906, San Francisco, California. The section of
the San Andreas fault shown here is 0.8 km north of
Woodville. The photo is looking northeast. The lateral or
strike-slip fault offset is large; however, the trace is
nearly invisible. This earthquake, together with the fire
that followed, resulted in more than 3,000 deaths and
400 million dollars of property damage. [Photo credit:
G.K. Gilbert, U.S. Geological Survey. Photo has been
colorized.]
What kind of fault is it?
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The footwall is on the left. Since the beds
indicate that the hanging wall has risen
relative to the footwall, this is a reverse
fault.
What kind of fault is it?
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If you stood on the fault plane, the
block on the right would be under your
feet. This is thus the footwall. The red
line marks equivalent layers on
opposite side of the fault. Since the
hanging wall dropped relative to the
footwall, this is clearly a normal fault.
http://facweb.bhc.edu/academics/science/harwoodr/Geol101/study/Images/ReverseFault.gif
Faults
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Reverse Fault – form as a results of
horizontal and vertical compression that
squeezes rock
Seen near convergent plate boundaries
Two areas end up closer together after
faulting
http://facweb.bhc.edu/academics/science/harwoodr/Geol101/study/Images/NormalFault.gif
Faults
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Normal fault – movement partly horizontal
and partly vertical
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Horizontal movement pulls rocks apart and
stretches crust
Vertical movement causes one side of rock to
move down relative to the other side
Two areas end up farther apart after
faulting
http://facweb.bhc.edu/academics/science/harwoodr/GEOL101/Study/Images/StrikeSlipRLFault.gif
Faults
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Strike-slip fault – caused by horizontal
shear
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Movement is mainly horizontal in opposite
direction
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Example: San Andreas Fault
Creates offset features after movement
Discuss:
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Evaluate how earthquake intensity is
related to the type of fault.
Bellringer:
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Contrast the three types of seismic
waves.
Earthquake waves
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Seismic waves = vibration of the ground
produced during an earthquake
Primary waves = squeeze and push rocks
in same direction wave is traveling
Secondary waves = cause rocks to move
at right angles relative to wave direction
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Slower than P waves
Surface waves = cause most destruction
and take longest to past
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Slowest wave, only travel of Earth’s surface
Seismic Waves
http://www.seismo.unr.edu/ftp/pub/louie/class/100/waves.GIF
Earthquake
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Focus = point where waves originate
Epicenter = point on surface directly above
focus
http://stevekluge.com/geoscience/images/epicenter.jpg
In-Class Assignment/Homework