Download Earthquakes

Warm-up 10/11
Pass back and go through Quiz!
Announcements
• Earthquakes and Volcanoes test is FRIDAY!
• Review (maybe do quiz corrections) and
STUDY your quiz and notes before then!
• Turn in your signed sheets for the National
Parks Project!
Earthquakes
Oct 11, 2010
Warm-up 10/11
Discuss:
• What type of plate boundary creates
Earthquakes?
• What do you think causes the earth to shake
during an earthquake?
Objectives
• I will be able to describe an earthquake’s
features such as epicenter, focus, magnitude,
and intensity
• I will be able to analyze the energies of seismic
earthquake waves
• I will be able to determine earthquake
location from a travel-time graph
Key Points
• To describe the location of earthquakes, we use the
terms focus and epicenter
• When analyzing how earthquakes travel, we talk about
the 3 main types of earthquake waves: s, p, and surface
– These waves travel at different speeds and cause differing
amounts of destruction
– The magnitude of an earthquake measures the amplitude
of the largest wave
• Major earthquakes can be preceded by foreshocks and
followed by aftershocks
• The intensity of an earthquake describes the amount of
shaking at a specific location
What are Earthquakes?
• Earthquake video
• Take note of at least 4 facts
1.
2.
3.
4.
______________________
______________________
______________________
______________________
Cause of Earthquakes
• What causes earthquakes to occur?
• Where do we usually find earthquakes
occurring?
Cause of Earthquakes
• Earthquakes are the vibration or shaking of the
Earth produced by the rapid release of energy
• When rocks are subjected to large forces, such as
those associated with plate movement, the rocks
are stressed and strained
• When rocks cannot withstand the stress any
longer, they break or shift and energy is released
• Faults are fractures in the earth where movement
has occurred
• Energy release  Vibrations  Earthquakes
Earthquake features
1. Location
– Focus: the place where the earthquake starts- the
source
• Energy radiates out in all directions
– Epicenter: the location on the surface of earth
directly above the focus
Earthquake features
2. Foreshocks: smaller earthquakes that precede or come
before major earthquakes
3. Aftershocks: smaller earthquakes that occur after
major earthquakes
4. Intensity: the amount of shaking produced by an
earthquake at a given location
5. Magnitude: the “size” of the earthquake
- Richter magnitude: determined from the amplitude
(height) of the largest seismic wave
- Moment magnitude: determined from the
displacement (movement) of the fault zone
Earthquake Waves
• All of the above features are a result of the
earthquake waves that transport the energy
from the focus outward in all directions
• Two general categories
– Surface waves: travel along Earth’s surface
– Body waves: travel from the focus through Earth’s
layers
Earthquake Waves
• Surface waves
– Travel along Earth’s outer layer
– Their motion is complex
• Like waves move a ship on the ocean
• Up/down and side-to-side motion
– The most destructive type of earthquake wave
• Because they travel along the ground they cause
anything resting on the land to move
Earthquake Waves
• Body waves- 2 types
1. P-waves
• Primary waves- they arrive first
• Travel the fastest
• Classified as “compressional waves”push-pull motion
• Can travel through solids, liquids, and
gases
Earthquake Waves
• Body waves
2. S-waves
• Secondary/seismic waves- they arrive
after P-waves
• Travel more slowly than P-waves
• Travel at right angles to the direction
they move
• Travel through solids only
Check In – Answer the following on a
SEPARATE piece of paper in COMPLETE
sentences:
1. What is the epicenter of an earthquake?
2. What is the source of an earthquake called?
3. What are the smaller earthquakes that precede
major earthquakes called?
4. Which type of seismic wave travels the fastest?
5. Which type of seismic wave travels the slowest?
6. Which type of seismic wave causes the most
destruction?
7. What is the amount of shaking produced by an
earthquake at a given location?
Locating Earthquakes- Part I
• Because P-waves and S-waves travel
at different speeds we can use the
difference in their arrival times at a
given location to figure out the
distance to the earthquake’s
epicenter
• This information is presented in a
travel-time graph
Reading Travel-time graphs
A. Time in minutes for
the arrival of the waves
B. Distance from the
recording station to the
epicenter
- kilometers at the top
- miles at the bottom
To find when a wave will be received
when given the distance between the
seismic station and epicenter…
1. Find the distance along the x-axis
** make sure you are using the correct units
** look at the top and bottom
2. Follow the distance line up to where it meets
the S-wave or P-wave curve.
3. Go across to the y-axis to find the time
• When will the
first P wave be
received if an
earthquake
epicenter is
approximately
3000 kilometers
from the seismic
station?
_____________
_____________
To find the distance between the
seismic station and epicenter given
the arrival time of one wave…
1. Find the arrival time along the y-axis.
2. Follow that time across until you hit the
wave curve line.
3. Go down/up to the distance
– make sure you check your distance units!
• If the first S
wave arrives
after 9
minutes, what
is the distance
between the
epicenter and
seismic
station?
____________
To find the distance between the
seismic station and epicenter given
the difference in arrival times
between s-waves and p-waves…
1. Look at the S-wave curve and P-wave curve
to find where they are separated by the
amount of time given.
2. Follow that line down/up to the distance in
the appropriate units
Ex: difference in p wave and s wave arrival time
is 5 min. How far is the seismic station from
the epicenter in miles?
• What would
the difference
in travel times
between the
first P-wave
and first Swave be if the
seismic station
is 1500 miles
from the
epicenter?
____________
To find the difference in wave arrival
time given the distance between the
seismic station and epicenter…
1. Find the distance along the x-axis
2. Follow the distance line up to the P-wave
and S-wave curves.
3. Using the times on the y-axis, calculate the
difference in arrival times of the two waves
• What would
the difference
in travel times
between the
first P-wave
and first Swave be if the
seismic station
is 4000 km
from the
epicenter?
____________
Warm Up 10/12
• You DO NOT need your computers for the
warm up today. It will be done on a separate
piece of paper.
• Be prepared for a brownie ticket and then a
warm up on paper.
Brownie Ticket
1. When an earthquake occurs, energy radiates in all
directions from its source, which is the called the ___.
A. Focus
B. epicenter
C. Fault
D. Seismic center
2. Which seismic waves travel the most rapidly?
3. Major earthquakes are sometimes preceded by smaller
earthquakes called ___.
4. The amount of shaking produced by an earthquake at a
given location is called the ___.
A. intensity
B. magnitude
C. epicenter
D. Richter scale
Earth Revealed
• Answer the questions on the worksheet as
you watch a video about EARTHQUAKES!
Study Guide
• Use your notes or the teacher notes for
Volcanoes and Earthquakes to complete the
study guide.
• Your test is on FRIDAY.
• Your study guide is due FRIDAY for a QUIZ
grade!
Warm-Up 10/13/10
• The Richter magnitude of an earthquake is
determined from the ___.
A.
B.
C.
D.
Duration of an earthquake
Intensity of an earthquake
Arrival times of P waves and S waves
Measurement of the amplitude of the largest
seismic wave
• What is the epicenter of an earthquake?
• Which seismic waves travel the most rapidly?
• Which are the most destructive?
O
Objectives
• Today I will be able to:
– Analyze the number of seismic stations necessary
to locate an earthquake epicenter
– Describe other natural side effects of earthquakes
– Analyze how earthquake waves provide
information about earth’s interior
– Describe earthquake safety measures
Locating Earthquakes- Part II
• Using earthquake waves to locate an epicenter
• ESSENTIAL QUESTION WHILE YOU’RE
WATCHING…
HOW MANY SEISMIC STATIONS WOULD YOU
NEED TO ACCURATELY LOCATE AN
EARTHQUAKE EPICENTER? _____________
Other useful information from
earthquake waves
• Earthquake waves tell us the location of an
earthquake’s epicenter and focus
• Earthquake waves also tell us about the make up
of the Earth’s interior
– This information is available because s- waves and pwaves travel at different speeds and are able to pass
through different materials
• BOTTOM LINE: most of the information we
know about the earth’s interior was obtained by
studying earthquake waves.
Effects of Earthquakes
• Main effect of earthquakes… A lot of
destruction
• Side effects:
– Tsunamis- “seismic sea waves” triggered by
earthquakes occurring underwater
• Ocean waves caused by submarine earthquakes
– Landslides- ground movement and liquefaction
– Fires- broken gas lines and electrical wires
Effects of Earthquakes
• San Francisco Earthquake 1989
• Look at how widespread the effects of the
Earthquake are!
Effects of Earthquakes
• Where did you see the earthquake affecting
people?
• At some of these locations and other locations
in the area, people were seriously injured… At
other location people were alright.
• Watch this next clip to figure out why
• Destruction in California Earthquake
Earthquake Safety
• Structures that withstood the shaking…
– Candlestick park
• Built on reinforced bedrock
• Structures that did not withstand the shaking…
– Bay Bridge- too stiff and not well reinforced
– Freeway in Oakland- not flexible or reinforced
– Landfill
• Soft land
• Buildings sank and collapsed, water and gas lines broke
Earthquake Safety
• Buildings can sink!?
– The process is known as liquefaction
– Let’s see how it works
– Liquefaction
Bottom line: The safest location during a major
earthquake would be an area with solid bedrock…
and if possible a location that has been reinforced
Check In – Answer on a separate piece
of paper in complete sentences:
1. Most of the information about Earth’s interior
was obtained by studying what?
2. What is the minimum number of seismic
stations needed to determine the location of an
earthquake?
3. Describe the type of building that would be
safest during an earthquake.
4. How would the lives of people living in areas
affected by tsunamis be effected if earthquakes
stopped happening?
Recent Earthquakes
• Listen as I describe and we watch footage from recent
earthquakes in Haiti and Chile.
• Both suffered devastating Earthquakes this year, while
you watch thing of things they have in common and
things that are different about them.
– http://www.boston.com/bigpicture/2010/01/earthquake_i
n_haiti.html
– http://www.boston.com/bigpicture/2010/02/earthquake_i
n_chile.html
Venn Diagram
1. On a half sheet of paper, create a Venn Diagram
comparing the earthquakes.
–
–
–
4 things only about haiti
4 things only about chile
4 things in common
2. WRITE A PARAGRAPH (5-8 sentences long)
describing the earthquakes and their
destruction using key terms from yesterday and
today IN YOUR OWN WORDS on the back of the
diagram.
Study Guide
• When finished work on your study guide for
the TEST on FRIDAY!
Brownie Ticket
1. What is a tsunami?
2. Which of the following would most likely be the safest
during a major earthquake?
A.
B.
C.
D.
Area with loosely consolidated soil
Area with structures built on a landfill
Area with granite bedrock
Area with steep slopes of unconsolidated sediments
3. Most of the information about the Earth’s interior was
obtained by studying ___.
A.
B.
C.
D.
Rocks of the ocean crust
Earthquake waves
Meteorites
Rocks in deep wells
4. What is the minimum number of seismic stations needed
to determine the location of an earthquake’s epicenter?
Warm Up 4/9
1. A succession of ocean waves set in motion by
a submarine earthquake is called what?
2. Most of the information about Earth’s
interior was obtained by studying what?
3. When an earthquake occurs, energy radiates
in all directions from its source, which is
called the ______________.
4. What type of area would be safest during a
major earthquake? Explain.
Study Guide Collection
• Pull out your study guides.
• Are there any questions that you need help?
• I will go over 3 of them with you as a group
before we turn them in.
Review
• For the review before the test, we will play
jeopardy.
• I will set the timer for 15 minutes. When the
time is up, the game is over.
Test!
• When you complete the multiple choice
question, answer the following ESSAY question
in 5-8 complete sentences.
• Explain how Plate Tectonics are related to
earthquakes and volcanoes. How do these
events affect our planet and human
civilization?
Article Report
• Complete the article report. Follow the
instructions on the paper provided.
• While you are doing this I will be passing out
progress reports. It must remain silent so that
I can talk to each of you about your current
grades.
National Parks Project
• Explain that we will be doing a project over
the next two weeks.
• It will be due on April 22, 2010.
• More details to come next week.