Chapter # 5 Study Packet: Earthquakes
1. Types of Faults
http://www.iris.edu/gifs/animations/faults.htm
*Type of fault: ________
*Stress Force: _________
*Movement along fault: ________________
____________________________________
_____________________________________
Type of Fault: ______
Stress Force: _______
Movement along Fault: ______________
__________________________________
*Type of Fault: _________
*Stress Force: __________
*Movement along Fault: __________
____________________________
2. Investigating Plate Movement and Faults:
Fault Line
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Where do most earthquakes take place? Explain why.
______ ______ _____ That is where________, _____ _____ _______,
mountain building, and strike-slip movements take place.
When is more energy released by a fault, when the fault slips easily and
frequently or when it ruptures suddenly?
increased resistance = ______ stress = sudden movement (rupture) =
______energy
Why do some faults rupture suddenly?
Twists or “kinks” in parts of the fault lock the fault until enough _____
builds up causing the fault to _______ and release more energy causing
strong earthquakes.
3. Simulating the motions of Seismic Waves:
__?__ Wave: These seismic waves travel straight outward from the focus
?
compressing and expanding the rocks and ground they move through.
?
__S__ Wave: These seismic waves vibrate from side to side and up and down
as they travel through the rocks and ground.
4. Locating the Epicenter of an Earthquake:
Location of an Epicenter
Seismogram
A ____________ is a geophysicist that study’s earthquakes. In order to locate
the _________ of an earthquake, a seismologist needs to examine seismograms recorded
by _______different seismograph stations. On each of these seismograms, seismologists have
to measure the difference in S – P arrival times (time interval) (in ______ or minutes). The S - P time
interval is the amount of time
that passes between the arrival of the P wave and the subsequent S wave. This interval will then be used to
determine the ________the waves have traveled from the origin to that station. This interval
determines the distance the waves have traveled, but gives no indication of the ________ from
which they came. The seismologist only knows that the earthquake took place somewhere along a circle
having a radius equal to the distance indicated. That is why information from three different seismograph
stations is necessary to locate the earthquake’s ____________.
If the difference in arrival time is 4
minutes, what is the distance to the
epicenter?
A.
B.
C.
D.
2200 km.
2300 km.
2600 km.
2800 km.
5. The San Andreas Fault: http://pubs.usgs.gov/gip/earthq3/contents.html
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What kind of fault is the San Andreas Fault?
__________________________________
Which two plates meet to form the San Andreas Fault?
__________________________________________
Where is the San Andreas Fault located?
____________________________________________________
6. Analyzing Earthquake Graphs:

Were there more magnitude 2.5 or greater
earthquakes in 1986 or 1987?
_______

What year recorded the greatest number of
magnitude 2.5 or greater earthquakes?

______
Since 1973, does the number of magnitude 2.5 or
greater earthquakes seem to be decreasing,
increasing, or staying the same.
__________________________________________
7. The Richter and Mercalli Earthquake Scales:

When an earthquake has a magnitude of
7.0 according to the Richter Scale, what
types of observable damage will you see
according to the Mercalli Scale?
_______________________________
___________________________________

The Mercalli Scale indicates that a tremor
was noticed by many people, but the people
often don’t realize it is an earthquake. What
would the magnitude of this earthquake be
according to the Richter Scale.
_________________________

An aftershock occurs several hours after an earthquake and is felt by everybody. Many people run
outdoors. Furniture moves and items fall off of shelves, but overall only slight damage occurs. What
number would this earthquake rank on both the Mercalli and Richter Scales?
_________________________________________________________________________
8. Mountains Formed by Folding and Faulting:
Example:
Teton Range
Mountains Formed by Folding
Mountains Formed by Faulting
Over millions of years, fault movement can change a flat plain into a towering _______ range.
______________ Mountains such as the _______ Range near the border of Wyoming and
Idaho. Mountains can also form by the ________ of rocks due to the force of _____________.
Geologists use the terms anticlines and synclines to describe upward and downward folds in rock layers. A
fold that bends upward into an arch is called an __________. A fold in rock that bends downward in
the middle to form a bowl is called a __________
9. Earthquake Hazards and Safety:
http://dsc.discovery.com/guides/planetearth/earthquake/interactive/interactive.html
Earthquake engineers build sky scrapers and homes in California which is an area that is prone to
earthquakes. Their goal is to create structures that are resistant to Earthquakes. Engineers first evaluate the
________ on which the structure will be constructed. Engineers also use improved
___________ methods to add stability and strength to structures.
Construction Methods
Reinforced building materials
give concrete and masonry
structures more tensile
strength.
Foundation anchoring
keeps a structure and its
base moving as a unit
when the ground begins
to quake.
Pile foundations reach
down through unstable
soil to the bedrock
beneath for added
stability.
*This is just one example.
(see PH text pg. # 165)
Base isolation allows a
structure’s foundation and the
ground move as one, minimizing
the forces on the building itself.
Animation link:
http://www.sciencelearn.org.nz/con
texts/earthquakes/sci_media/video/
how_base_isolation_originated
Types of Ground
Coastal ground quality
varies. When near water,
there are many dangers to
consider.
Loose, gravely soil.
Prepare to go deep for
support.
Building along a fault zone
has its risks but is often
unavoidable.
10. Tsunamis:
Definition: A tsunamis is an unusually large sea
_______ produced by a seaquake or undersea volcanic
eruption.
Animations Link:
http://www.pbs.org/wnet/savageearth/animations/tsunami/main.html
Stable, solid ground such
as solid bedrock seems
safest, but in a quake-prone
area, all construction is a
calculated risk.