Seismic Sleuths

Earthquakes

A Teachers Package for Grades 7-12
 
Unit Two (continued)

2.4 Earthquake Hazards

ACTIVITY ONE
LIQUEFACTION: THAT SINKING FEELING

RATIONALE
Like other earthquake-related phenomena, liquefaction may cause the 
loss of property and even injury or death. This model allows 
instructors and students to observe the effects of liquefaction and the 
phenomenon of sand boils on a small scale.

FOCUS QUESTIONS
What happens when a damaging earthquake strikes areas prone to 
liquefaction?

OBJECTIVES
Students will:
1. Construct a model to demonstrate liquefaction.
2. Distinguish between soil liquefaction and soil saturation.
3. Assess potential damage to homes, lifelines, and schools.

MATERIALS
for the teacher
 Master 2.4a, Teacher Background Reading: Liquefaction
 Master 2.4b, New Madrid Narrative

for each small group
 226 g (about 8 oz) of well-sorted fine sand [Sandbox sand works well.]
 One .25-1 (9 oz) clear plastic cup
 One pie plate, diameter 23 cm (9 in.)
 225 ml (5 oz) of water in a pitcher
 Sinker or comparable small object weighing at least .06 kg (2 oz)
 One 250-ml beaker
 Newspapers to cover work surface

TEACHING CLUES AND CUES
If possible, substitute a small, hollow, ceramic house, measuring approximately 
5 x 5 x 7 cm, for
the sinker. These are sold at hobby shops for Christmas scenes, and can be 
filled with BBs to add weight.

PROCEDURE
Teacher Preparation
Read Master 2.4a, Teacher Background Reading: Liquefaction, and 
Master 2.4b, New Madrid Narrative. Decide how you will share this 
information with your students. Students who like to read will find 
New Madrid Narrative delightful.
Gather enough materials so you can have two students per station. 
Before class, cover work areas with newspapers, set up the stations, 
and practice each activity at least once to be sure everything works.

A. Introduction
Tell students that an earthquake with a magnitude of 5.0 or greater 
may cause saturated sand or clay soils to liquefy. During the winter 
of 1811 and 1812, a series of earthquakes affected the central portions of the 
United States that we now know as Missouri, Arkansas, 
Kentucky, Illinois, and Tennessee. As the soft sediments along the 
rivers were violently shaken, tremendous volumes of sand were liquefied and 
ejected onto the Mississippi River flood plain. These sand 
boils, as they are called, are still visible in the rural countryside today. 
Fortunately the area of the earthquakes was not heavily populated in 
1811-12, so loss of life, injuries, and loss of property were minimal.

During the 1989 World Series in San Francisco, a 7.1 earthquake 
struck the Bay Area. Millions of people viewed firsthand the fires and 
severe damage to buildings in the Marina District. Some of this 
damage occurred because soil liquefaction caused lifelines to rupture 
and buildings to collapse.

TEACHING CLUES AND CUES
Students may be aware that the flooding of the Mississippi and Missouri Rivers 
in the summer of
1993 caused mud boils in some places. Explain that these eruptions, 
somewhat similar to sand boils, were caused by extreme saturation of 
muddy soils in combination with the force of the torrential rains. Mud 
boils, like sand boils, can also be caused by earthquakes over 
magnitude 5.0.

VOCABULARY
Consolidated: tightly packed, composed of particles that are not 
easily separated.

Ground water: subsurface or underground water.

Lifeline: a service that is vital to the life of a community. Major lifelines 
include transportation systems, communication systems, water 
supply lines, electric power lines, and petroleum or natural gas pipelines.

Liquefaction: the process in which a solid (soil) takes on the 
characteristics of a liquid as a result of an increase in pore pressure and 
a reduction in stress.

Sand boil: a forcible ejection of sand and water from saturated soil, 
caused by an earthquake or heavy flooding.

Saturated: having absorbed water to the point that all the spaces between 
the particles are filled, and no more water can enter.

Unconsolidated: loosely arranged, not cemented together, so particles 
separate easily.

B. Lesson Development
1. Write the word liquefaction on the board, and ask student to 
identify its root work (liquid). Emphasize that liquefaction does not 
cause an earthquake, but is the result of an earthquake. Liquefaction 
occurs only in highly saturated sand or clay soils. An earthquake with 
a magnitude of 5.0 or greater is usually needed to cause liquefaction. 
Earthquake vibrations cause soil particles to lose contact with each 
other, so the soil takes on the characteristics of a liquid.

2. Assign a partner to each student and designate a work station for 
each team. Give these directions:
a. Cut off about 5 mm from the bottom portion of the plastic cup.
b. Invert the cup and place it in the middle of the pie pan.
c. Holding the cup firmly, slowly pour the sand into the bottom of the 
cup to a level of 10-20 mm from the top. (One student may hold while 
another pours.) Level the sand with your fingers. Do not shake the cup 
to settle or level the sand.
d. Lightly place the sinker, model house, or other weight onto the 
leveled surface of the sand.
e. Again holding the cup, slowly pour the entire 225 ml of water into 
the pie pan around the outside of the cup and sand.
f. Observe what happens and record the time it takes for the soil to 
reach saturation.
g. Once the soil is saturated, one student win hold the cup firmly in 
place while the other gives the side of the cup several sharp taps to 
simulate earthquake shaking. Observe what happens to the weight.

C. Conclusion
Help students to clean up and then initiate the discussion. Ask: If the 
weight in our experiment were an occupied building, and liquefaction 
occurred over a large inhabited area, as it did in the San Francisco Bay 
Area in 1989, what would be the effect on:
 People?
 Private homes?
 Schools?
 Buried lifelines (gas, water, electrical, oil, sewage)?
 Agricultural lands?
 Medical facilities, fire stations, police stations?
 Large urban areas (Memphis, San Francisco, Boston)?
 Industrial areas?
 Materials that had been discarded in old sand boils? (These could 
range from dead cows to old refrigerators to poisonous waste.)

ADAPTATIONS AND EXTENSIONS
1. Make sand of various particle sizes and objects of different masses 
available for student experiments. Investigate the degree of 
liquefaction each will exhibit and the effects on the structures that rest 
upon them. (A layer of diatomaceous earth under the sand will bubble 
up when the table is rapped. Try it!)

2. Invite students to find ways to vary the amount of force they apply 
to the sand and water mix in the model.

3. Provide an aquarium or plastic gallon jars so students can 
experiment with larger models. Use transparent containers of any 
sizeeven a plastic sandwich boxfor an interesting side view.

4. Bury objects in the sand and observe the results.

5. Develop models of overhead power lines, pipelines, sewage lines, 
light posts, and highways, and observe how liquefaction affects them.

6. Challenge students with this question: If a building has already 
been constructed on soil that has a potential to liquefy, what can be 
done to reduce the likelihood of damage? Invite them to design and 
test model structures that would reduce structural damage during 
liquefaction.

ACTIVITY TWO
LANDSLIDES: SLIP-SLIDING AWAY

RATIONALE
Earthquakes dramatically increase the potential for landslides in areas 
where landslides are common, such as those where sedimentary rocks 
lie just under the soil. Structures on cliffs and ridges need to be 
designed to the highest earthquake standards, and should be fully 
insured.

FOCUS QUESTIONS
How can an earthquake trigger a landslide?
What factors affect the probability of an earthquake-related landslide?

OBJECTIVES
Students will:
1. Construct a model to simulate an earthquake-related landslide.
2. Investigate the variables that affect an earthquake-related landslide, 
such as the strength of the slope materials, the steepness of the slope, 
and the intensity of ground shaking.
3. Explain why the steepness of a slope determines how the force of 
gravity acts on an area of ground and how it is related to frictional 
forces.

MATERIALS
for the teacher
 Slides or photos of landslide damage (in your geographic area, if 
available)
 Slide projector and screen or blank wall space (optional)
 Pasteboard or cardboard arrows in three colors, cut to the correct 
lengths to illustrate the 30 angle (optional)

for each small group
 A pine board, approx. 2.5 cm x 25 cm x 1.0 m (1 in. x 10 in. x 3 ft.)
 A meter stick
 Two plastic dishes, approx. 19 cm in radius, with sides 3.5 cm high
 Enough dry sand to fill the two dishes
 500 ml of water in a beaker or other suitable container
 Newspapers to cover work surfaces
 A sensitive bathroom scale that can register weights as low as 1 
Newton (less than 2 lbs)
 Paper towels for cleaning the board between trials
 Master 2.4c, Landslide Data Table
 Master 2.4d, Landslide Activity Sheet
 Pencils or pens
 Transparency made from Master 2.4e, Components of the Force of Gravity
 Overhead projector
 Soil, gravel, or other materials for the extension (optional)

TEACHING CLUES AND CUES
The width of the board can vary, but it must be 1 m long.

The inexpensive clear plastic dishes sold to put under potted plants will 
be ideal. The dish must be a little smaller than the board.

VOCABULARY
Friction: mechanical resistance to the motion of objects or bodies that 
touch.

Gravity: the force of attraction between any two objects with mass. 
Gravity is especially noticeable when an object of great mass, such as 
Earth, attracts an object of lesser mass.

Landslide: an abrupt movement of soil and bedrock downhill in 
response to gravity. Landslides can be triggered by earthquakes or other 
natural causes.

Loess: an unstratified, windblown mixture of clay, sand, and organic 
matter usually crumbly and buff or yellow-brown in color.

Mass movement: the movement of surface material caused by gravity.
Variable: in a scientific experiment, the one element that is altered to test 
the effect on the rest of the system.

PROCEDURE
Teacher Preparation
Assemble slides and/or photos. Assemble the other materials ahead of 
time and experiment with them to get a feeling for how various angles 
will affect their movement. Cover work surfaces with newspapers.

A. Introduction
Ask the students: Can an earthquake cause a landslide? Promote a 
discussion of their experiences and ideas. Show any images you have 
gathered of earthquake-related landslides, especially those that have 
affected your local environment.

Explain to the students that not all landslides are earthquake related; 
many are caused by other natural factors. Landsliding, or mass movement, occurs 
when the forces that hold materials in place are exceeded 
by the force of gravity in the direction of motion. The forces that hold 
sand, soil, rocks, and buildings in place are related to the strength of 
the materials. The balance of these forces may be affected by the 
intensity of ground shaking during an earthquake. The steepness of the 
slope on which the materials rest determines how much the force of 
gravity acts in the direction of motion.

B. Lesson Development
1. Divide the class into cooperative groups of three or more students. 
Distribute one copy of Master 2.4c, Landslide Data Table, to each 
group. Ask one member from each group to collect a dish of sand and 
the other materials.

2. Tell the students they will be conducting this investigation in a 
scientific manner. That is, they are to control the variables, manipulate 
only one, and measure or observe the response. When students have 
completed the experiment, it is very important that they use only their 
results to develop an explanation and that their explanation relates only 
to this particular model. Point out that the questions toward the end of 
the Landslide Activity Sheet relate to the scientific process they are 
employing.

3. Instruct students to set up a ramp, as illustrated on Master 2.4c, and 
begin to explore the effect of the ramps angle on the weight the scale 
reads. Explain that the less weight the scale records, the greater the 
force of gravity parallel to the ramp and the weaker the force of 
friction that holds the material in place. Give these instructions:
a. Place the scale at the bottom end of the ramp and place a dish of 
sand right side up on top of it.
b. Raise one end of the ramp to the height corresponding to the first 
angle indicated on the Landslide Data Table. As you move from one 
angle to another, record the scale readings in the Landslide Data Table.

TEACHING CLUES AND CUES
If you do not have enough scales you may do this section as a 
demonstration. You may also choose to simply describe the 
forces and use the factors in the data table below to describe how the 
measured weight of the material changes as the angle of the ramp 
changes. Whether you do the weighing or the students do, be sure 
to convert pounds into the metric unit Newtons (2.2 pounds = 9.8 
Newtons).

4. Stop the groups when they have completed the scale measurements 
and explain that the ramp breaks the force of gravity up into two 
components. Project the transparency of Master 2.4e, Components of 
the Force of Gravity, to illustrate. One of the components operates in 
a direction perpendicular to the ramp; that is the force they just 
measured. The other force operates along the ramp. That is the force 
of gravity, which will cause the landslide. These two components of 
gravity form two sides of a right triangle. Depending on the angle of 
the ramp, the force of friction may or may not cancel the force of 
gravity.

TEACHING CLUES AND CUES
If you made the arrows listed in the materials section, use them now to 
help students visualize these angles. Explain that the science of trigonometry 
deals with 
the mathematics of right triangles. Here you will simply measure and 
calculate the forces.
 
From 0-20 degrees not much will happen, but above 20 degrees, the 
students should begin to see some distinct motion.

5. To investigate the effect of slope on material with and without a 
simulated earthquake, ask the students to remove the scale. Show 
them how to place the dish of sand upside down at one end of the 
board without spilling the sand. First, place the board on top of the 
dish. Then, while holding the board down over the dish, carefully flip 
the board over. The dish should be upside down on the board with all 
the sand still in the dish.

6. When all the groups have accomplished this, ask students to vary 
the angle of the ramp as they did before, this time by slowly raising 
the end of the board with the dish of sand. Instruct students to record 
the height at which the sand starts to slide, then lower the ramp by 
about 5 cm and tap on the ramp to simulate an earthquake.

7. Give these instructions to test the effect of water on the sand:
a. Again cover the dish with the board, flip the dish right side up, and 
add 225 ml of water to the sand.
b. Flip the dish of wet sand back onto the ramp and repeat step 6 to 
see the effect each new angle of the ramp has on the wet sand.
c. Continue to record your data and observations in the Landslide Data 
Table. Use the transparency of Master 2.4e, Components of the Force 
of Gravity, and Master 2.4d, Landslide Activity Sheet to answer the 
questions about force.

C. Conclusion
Allow time for students to respond to the last questions on the 
Landslide Activity Sheet, which ask them to develop an explanation 
for what they have observed. When they have finished, ask the groups 
to share their explanations, being certain to justify their explanations 
by citing their data.

Ask the class if they think the work they have just done is similar to 
what scientists do. Ask them what the scientific community would do 
with a variety of explanations and varying data for the same 
procedure. Impress upon students that their investigation is one aspect 
of science and their reporting is another. Explain that it would take a 
great deal of time and many replications for any of their explanations 
to be accepted as a landslide theory. If they try the extension activities 
and want to carry their investigation of landslides still further, they 
will have to connect this model to real landslide data.

Finally, review and summarize the forces involved in landslides, 
referring to the illustrations on the handouts. Show the photos or 
slides again, and ask students to explain what they observe in terms of 
physical forces.

ADAPTATIONS AND EXTENSIONS
Invite students to test the effect of the material by repeating steps 6 
and 7 above with dishes of potting soil, gravel, and other materials.

ACTIVITY THREE
TSUNAMI: WAVES THAT PACK A WALLOP

VOCABULARY
Amplitude: a measurement of the energy of a wave. Amplitude is the displacement 
of the 
medium from zero or the height of a wave crest or trough from a zero point.

Period: the time between two successive wave crests. Run-up elevation or height: 
the 
highest attitude above the tide line, in meters, that the water reaches as it 
is forced up on land by a tsunami. Seismic sea wave: a tsunami 
generated by an undersea earthquake.

Tsunami: a potential destructive ocean wave created by an earthquake or other 
large-scale 
disturbance of the ocean floor. This Japanese word has the some form in 
both the singular and the plural.

Wave crest: the highest point a wave reaches. The lowest point is called its 
trough.
Wave height: the vertical distance in meters from a waves crest to its 
trough. (This measurement will be twice the amplitude measured for the 
some wave.)

Wavelength: the horizontal distance between two successive crests, often 
measured in meters.

RATIONALE
Underwater earthquakes can cause very powerful seismic sea waves 
commonly called tsunami or (incorrectly) tidal waves. These waves 
can devastate a coastal community because of the tremendous amount 
of energy they carry.

FOCUS QUESTIONS
How do earthquakes cause seismic sea waves?
What kinds of energy transfers are involved?
What precautions can people take to limit tsunami damage?

OBJECTIVES
Students will:
1. Prepare and present a class report that reflects their own research 
on seismic sea waves.
2. Describe the characteristics of an average seismic sea wave in 
terms of speed, wavelength, and period, and predict its effects on a 
coastal community.
3. Calculate the energy of the disturbance (sea floor motion) that 
causes an average seismic sea wave.

MATERIALS
 Master 2.4f, Teacher Background Material
 Student copies of Master 2.4g, Tsunami Event Reports
 Student copies of Master 2.4h, Seismic Sea Waves Activity Sheet
 Transparency of Master 2.4i, Wave Characteristics and Energy
 Overhead projector
 Student copies of Master 2.4j, Seismic Sea Waves Energy Analysis
 Copies of Master 2.4k, Seismic Sea Waves Research and Report 
 Form, one for every two students
 A large coil, telephone cord, or hose for demonstrating wave action
 Numerous student copies of Master 2.41, Grading Matrix
 Poster board or chart paper, markers, and audiovisual equipment as 
available
 Video camera (optional)

PROCEDURE
Teacher Preparation
Read the teacher background information on tsunami. Locate some 
before and after photos of tsunami, and either make transparencies or 
have them available to pass around the room.

Check your school and community libraries for the periodicals listed at 
the end of this lesson and in the Unit Resources. Also look for beginning 
oceanography textbooks and back issues of Scientific American.

TEACHING CLUES & CUES 
You may want to review scientific notation before handling the large 
numbers in this activity.

A. Introduction
If you have photos, share them with the class. Then pass out copies of 
Master 2.4g, Tsunami Event Reports. Have students take turn reading 
the accounts aloud. Ask students what they think causes tsunami.

B. Lesson Development
1. To provide the students with some common language, pass out 
Master 2.4h, the Seismic Sea Wave Activity Sheet, and help the class 
work through it. Project the upper half of Master 2.4i, Wave 
Characteristics and Energy. Ask students to tell you what belongs in 
each blank, and label the wave form accordingly. Point out that waves 
never stand still, so we have to be very clever to measure their 
characteristics.
2. Pose this question: How can a fault movement of only one meter in 
the depths of the ocean cause a huge wave to strike land? Promote 
student discussion until someone mentions the energy involved. At 
that point, project the lower half of Master 2.4i, and show students 
how the uplift of one meter actually involves lifting a column of water 
the same size as the area of seafloor uplifted.
3. Pass out copies of Master 2.4j, Seismic Sea Waves Energy 
Analysis. Work through the activity as a class or have students 
complete the worksheets in pairs, depending on their previous 
preparation.

TEACHING CLUES & CUES
You may want to videotape the presentations by setting the camera up 
on a tripod very close to the presenters. If you film your first 
class, you can use the footage to show other classes what you are 
looking for.

4. Challenge students to explain how a wave that is only one meter 
high in the ocean can grow so high as to overwhelm the land. Again 
direct their attention to the lower half of 2.4i, and point out the energy 
involved. (As the wave nears shore, in shallow water, the energy is 
forced upward, or refracted. See Master 2.4f for more detail.)

5. Invite students to do some research on actual tsunami drawn from 
the table of Notable Tsunami (below) or from other sources. Hand out 
one Seismic Sea Waves Research and Report Form (Master 2.4k) to 
every two students, explaining that each team is to research a specific 
topic and report what they learn to the class. Two students will report 
on tsunami warning systems; the others will report on a particular 
tsunami drawn from the list below. Set a due date and establish how 
you are going to evaluate the report. If you will use the matrix 
provided, explain it now.

Notable Tsunami by Place Reported

November 1, 1755	Lisbon, Portugal
April 2, 1868	Hilo, Hawaii
June 15, 1896	Sanriku, Japan
August 13, 1868	Arica, Peru
August 27, 1883	Java, eruption of Krakatau (also spelled Krakatoa)
March 2, 1933	Sanriku, Japan
April 1, 1946	Hilo, Hawaii
March 9, 1957	Hilo, Hawaii
May 23, 1960	Southern California
March 28, 1964	Crescent City, California
November 29, 1975	Hilo, Hawaii
May 26, 1983	Minehama, Honshu, Japan
July 12, 1993	Aonae, Japan

6. Invite discussion of preventive measures that can be taken to 
minimize seismic sea wave damage. As students progress in their 
research, they may be able to suggest guidelines. The presentations on 
early warning systems will address this topic directly.

7. When the due date for presentations is near, review how you will 
evaluate the presentations and specify the time limit for each. Provide 
poster board or chart paper and markers, overhead transparencies and 
pens, and slide or video apparatus if available.

C. Conclusion
Have the students present their reports. Before each presentation, 
distribute copies of the grading matrix. Ask students to use one matrix 
sheet for each presentation, taking notes in the space allotted and 
evaluating their peers presentations on the same criteria by which 
theirs will be graded. A respectful classroom atmosphere will ensure 
the success of these presentations.

ADAPTATIONS AND EXTENSIONS
Challenge one pair of students to research and describe the compressional waves 
that have been associated with underwater earthquakes in 
terms of the waves characteristics and its effect on ships.

2.4a Teacher Background Reading
Liquefaction

How Liquefaction Occurs during Quakes
Liquefaction happens during an earthquake when vibrations cause the pressures to 
build up in the ground water 
that occupies the pore spaces between the grains of sand, silt, or loess. The 
longer the duration of the earthquake, 
the more likely that liquefaction will be induced. The only solid strength of 
such a deposit is provided by the 
friction between grains touching each other. When the pressure in the water that 
fills the pore space between the 
grains is sufficient to spread them apart, the solid nature of the sand, silt, 
or loess deposit is changed into that of a 
viscous liquid: quicksand or quickclay.

Because it takes time for the pressures that produce liquefaction to build up 
underground, and because quicksand 
is a heavy, thick fluid that moves slowly, conditions of liquefaction, sand 
boiling, and associated phenomena may 
not he apparent during the shaking. In fact, they often do not manifest until 
after the shaking has already passed, 
sometimes not until 10-20 minutes later. The quick conditions or boiling of the 
sand can persist for hours or even 
days after the quake, sometimes as much as a week.

How Big Does It Take & How Near to the Quake?
A natural question regarding seismically induced liquefaction is how big an 
earthquake is required to induce 
quick conditions and how close it has to be for such effects to be possible. 
With regard to size, several technical 
publications suggest that liquefaction does not occur for earthquakes less than 
Richter magnitudes of 5.2. 
However, minor liquefaction effects in areas underlaid by particularly ideal 
predisposing conditions (loose sand 
deposits saturated with a near-surface water table) have been observed for 
earthquakes as small as 4.7 on the 
Richter scale in the New Madrid Seismic Zone. Minor damage to vulnerable 
structures has occurred in such 
areas.

With regard to distance, an earthquake in June of 1987 of magnitude 5.2 in 
southeastern Illinois caused 
liquefaction phenomena near Bell City, Missouri, 150 miles (240 km) from the 
epicenter. A swimming pool, two 
large grain bins, a carport, and three houses were damaged (one severely). There 
was also fissuring and lateral 
spreading. At the same time, points nearer the epicenter of that quake did not 
experience such ground failures. 
Three years later in 1990 this same area experienced no liquefaction phenomena 
when a 4.7 earthquake struck 
only 20 miles (32 km) away.

Nearness to the epicenter implies greater amplitudes of ground motion, but 
distance implies a longer duration of 
shaking, since the wave train consists of many waves traveling at a variety of 
speeds. The epicenter of the 
magnitude 8.1 earthquake that struck Mexico City in 1985 was 240 miles (384 km) 
away and induced 
liquefaction that severely damaged some buildings. Although lasting less than a 
minute at its distant source, that 
quake lasted several minutes in Mexico City. Ground shaking amplitudes within 
the city, were never large, yet 
400 buildings collapsed, resonating with the long-lasting wave train (or 
sequence of waves) amplified by 
underlying clays.

The New Madrid earthquakes of 1811-12 induced extreme examples of liquefaction, 
manifesting as sand boils 
and explosion cratering in the area of St. Louis, Missouri, and across the river 
in the flood plain of Illinois. 
Liquefaction also occurred from those quakes as far as Cincinnati, Ohio, more 
than 300 miles (480 km) away.

Three Ways to Induce Liquefaction
Liquefaction in soils can be stimulated three ways: seismically, mechanically, 
and hydrologically. Seismically-
induced liquefaction is caused by seismic waves. Mechanically-induced 
liquefaction is caused by vibrations that 
come from railroad trains, motor vehicles, tractors, and other mechanical 
sources of vibratory ground motion. 
Hydrologically-induced liquefaction occurs when ground-water pressures increase 
due to rising stream levels 
during flooding conditions. This type of liquefaction most commonly occurs on 
properties protected by levees, 
where rivers can rise to levels above the land surface without actually flooding 
the land. Most of the New Madrid 
Seismic Zone falls into this category, being surrounded by levees that flank the 
rivers and drainage ditches 
throughout the area. Because of this, seismically-induced sand boils became 
hydrologically active during river 
flood stages, and can turn into quicksand and boil again, just as they did 
during the earthquakes that formed them. 
Similarly, tractors, trains, and trucks crossing over sand fissures during times 
of high water table can 
mechanically induce liquefaction, causing highways to sag, railroad tracks to 
get out of parallel, and farm 
equipment to sink into the ground.

Note: Adapted from Stewart, David, and Knox, Ray, The Earthquake That Never Went 
Away: The Shaking Stopped in 1812, 
but the Impact Goes On, Marble Hill, MO: Gatlinburg-Richter Publications, 1993.

2.4b New Madrid Narrative
(A 1912 Account of the 1811-1812 Earthquakes)

The First Day
At 2:30 on the morning of December 16, 1811, a tremendous earthquake occurred 
whose epicentral region is thought to have 
been just west of the location of present day Blytheville, Arkansas, a city that 
did not exist at the time. Had it been there, it 
would have been devastated totally, as evidenced by the numerous earthquake 
boils and fissures that visibly surround the city 
today. The Richter surface wave magnitude is thought to have been 8.6. President 
James Madison, 800 miles (1280 km) away 
in the White House in Washington, DC, was shaken out of bed by the quake.

Many aftershocks immediately followed, some probably magnitude 6.0 or greater. 
At least two more of the December 16 
shocks are thought to have equaled 8.0 on the Richter scale.

Then, some time around 11:00 a.m., another great shock occurred in the vicinity 
of present-day Caruthersville, which to the 
residents there at the time seemed worse than the first. This one is thought to 
have been another magnitude 8.0. However, 
present-day Caruthersville wasnt there at the time. It was not founded until 
1857. In 1811 another village occupied that site. 
It was called Little Prairie, Missouri.

The River Rampages, and Towns Disappear
The Mississippi River was churned into a virtual maelstrom, with miles of banks 
caving in, boats being swamped and sunk, 
and even entire islands disappearing along with their human occupants.

Two towns disappeared at this time. One settlement to disappear on December 16, 
1811, was Big Prairie, Arkansas. At the 
confluence of the Mississippi and St. Francis Rivers, the town site liquefied 
and sank, but slowly enough for all residents to 
safely escape. There were about 100 people there at the time. The Mississippi 
River now occupies that site.
Another community destroyed that day was Little Prairie, Missouri, near present-
day Caruthersville. Eyewitness accounts of 
the horror tell us of people being violently thrown from their beds in the 
middle of the night. It had been a bright full moon, 
but shortly after the shock everything became pitch black because of the dust. 
People were injured and bleeding, and some 
were even knocked temporarily unconscious.

The earth continued to jerk and rumble through the darkness until daylight, 
when, around 8:00 a.m. the second hard shock hit 
the area. Throughout the morning more shocks continued, with the ground heaving 
and cracking, sometimes opening and then 
suddenly slamming shut, spewing ground water over the tops of tall trees. In 
some places the ground literally exploded, 
blasting debris high into the air, raining sand and carbonized wood particles 
down upon the heads of those nearby, while 
leaving a deep crater in the ground where smooth land had been before. Sometimes 
the earth formed spreading crevasses 
beneath the bases of large trees, splitting their trunks from their roots 
upwards beyond the levels of their limbs. At one point 
during the morning a great fissure began to form within the town. The 
townspeople stood around that pit and watched, 
horrified, as dark, viscous fluids gurgled from beneath the earth while gaseous 
fumes and the smell of sulfur and brimstone 
filled the air.

Many were thinking that the end of the world was at hand and that the very gates 
of hell itself were opening up to take their 
village. Amidst the terror, after the third great shock around 11:00 a.m., the 
soils of their settlement began to turn into 
quicksand, with dark waters oozing from the pores of the earth. As their whole 
town began to sink their streets and cabins 
were flooded, not from the river, but from the ground itself.

Escape from Little Prairie
Hastily, the residents of Little Prairie gathered what meager possessions they 
could hold, lifted small children to their 
shoulders, and waded westward. Looking ahead of themselves, they could see the 
rising waters far off on the horizon. For 
eight miles (12.8 km) they waded through waist-deep waters, never knowing from 
one step to the next if they were going to 
plunge headlong into an unseen crevasse or trip over a buried stump, all the 
while surrounded by snakes, coyotes, and other 
wild creatures swimming for their lives in that turgid flood. During their 
escape, they did not know if they would live through 
the day or not, but all did survive.

The First Day Was Over, but the Worst Was Yet to Come
What has been described, thus far, was only the first day of the Great New 
Madrid Earthquake series. More and bigger 
tremors were yet to come. At about 9:00 a.m. on January 23, 1812, another of the 
really big ones hit. This was probably 
centered north of Little Prairie and south of Point Pleasant, a small settlement 
there at the time. It is thought to have been an 
8.4 magnitude earthquake.

The Mississippi River bank, on which the village of Point Pleasant was situated, 
collapsed during the January 23 event. 
Fortunately, the residents had all evacuated the site prior to that catastrophe 
so that none were injured. The town, however, 
was lost forever.

The January 23 event also caused several huge sand boils in Tennessee that 
created a dam across Reelfoot Creek. This created 
Reelfoot Lake.

On February 7, 1812, came the largest quake of all. At about 3:15 in the morning 
the region was rocked by an 8.8 magnitude 
shock. Outside of Alaska, that is the largest earthquake in American history and 
one of the largest in the world.

This is the quake that caused the Mississippi River to run backwards. It caused 
such towering waves of water to be thrown 
over the banks that thousands of acres of trees were shattered into splinters 
and stumps. It threw boats up on dry land along St. 
Johns Bayou at New Madrid. And it created two temporary waterfalls. These falls 
had a vertical drop of about six feet (2 m) 
followed by a mile (2 km) or so of shallow rapids.

During the largest of the New Madrid earthquakes, the river is said to have 
boiled, whirled, and heaved with massive waves 
bashing from one bank to the other, sweeping boats and debris into oblivion. 
Some eyewitnesses from the banks said they 
actually saw the river open up in yawning chasms, into which the swirling waters 
disappeared, drawing hapless flat boats and 
their passengers into the maelstrom, never to be seen again. Others said water 
spouts would shoot upwards from the waters 
surface, like tall fountains.

The earthquakes had literally destroyed the landscape with sand deposits, 
crevasses, and permanent flooding. Most residents 
of the region abandoned their properties and moved away. The boot-heel portion 
of Missouri was nicknamed Swampeast 
Missouri sometime after the quakes.

Two More Towns Gone Forever
The February 7 quake destroyed two other towns, wiping them forever from the 
face of the earth. One was Fort Jefferson, 
Kentucky, swept away by landslides. These slumps are still visible today along 
Highway 51 leading into Wickliffe. The other 
lost town was New Madrid itself. What was left of the settlement slumped 
downward 15-20 feet (5-10 m) into the waters 
edge and was washed away by the spring floods of 1812.

The throbs and throes of terra firma wrought by the Great New Madrid Earthquakes 
of 1811-12 trouble us no more. Though 
the motions of these gargantuan ground vibrations ceased in 1812, their impact 
goes on. Permanent traces of their violence lie 
scattered over a 5,000 square mile (12,000 sq km) area spanning five states.

Note: This account was adapted with only minor changes from Fuller, Myron L., 
The New Madrid Earthquakes of 1811-
1812, A Scientific Factual Field Account, USGS Bulletin 494, Washington, DC: 
Government Printing Office, 1912; reprinted 
by Southwestern Missouri University Center for Earthquake Studies, 1990. Please 
keep in mind that the numerical Richter 
magnitudes quoted in this book were not determined by instrumental measurements 
as they are today, because these events 
predated the invention of reliable seismographs.

2.4c Landslide Data Table

2.4c Landslide Data Table (key)

2.4d Landslide Activity Sheet

Name

Group Names/Roles

1. Why do you think the scales measure less weight as one end of the ramp is 
raised?

2. At what height or what angle does the dry sand slide?

Why do you think it slides then, in terms of forces?

3. What effect does the simulated earthquake (knocking on the ramp) have on the 
dry sand?

Why do you think the simulated earthquake has that effect?

4. Before testing wet sand, what effect do you think wetting the sand will have 
on the slide angle? Why?

5. What effect did wetting the sand have on its slide angle? Why?

6. What effect does the simulated earthquake (knocking on the ramp) have on the 
wet sand?

7. How did you control the following variables?
a. height or angle
b. quantity of material
c. amount of moisture
d. surface condition
e. other

8. How did you insure that only one variable was changed at a time?

9. From your data, try to explain how earthquakes affect landslides in as much 
detail as possible.

10. How could you test your explanation?

11. What was interesting or unexpected in the investigation? Why?

2.4d Landslide Activity Sheet (key)

Date:

1.	Why do you think the scales measure less weight as one end of the ramp is 
raised?
	Some of the weight is acting along the ramp. The scale doesnt record that 
weight.	 
		
2.	At what height or what angle does the dry sand slide?
	40-50 cm, or about 30 degrees.	
	Why do you think it slides then, in terms of forces?
	The force of gravity along the ramp is greater than the frictional forces.
	 
		
3.	What effect does the simulated earthquake (knocking on the ramp) have on 
the dry sand?
	The sand slides a bit with each knock.	
	Why do you think the simulated earthquake has that effect?
	It must reduce the frictional forces because gravity remains constant.	  
		
4.	Before testing wet sand, what effect do you think wetting the sand will 
have on the slide angle? Why?
	It will probably slide more easily because the water reduces the friction.
	 
		 
5.	What effect did wetting the sand have on its slide angle? Why?
	The sand seemed to stick to the ramp, so it required a sharper angle to 
make it slide.	 
	Surface tension causes the sand to adhere to the ramp.	 
		
6.	What effect does the simulated earthquake (knocking on the ramp) have on 
the wet sand?
	It slid further with each knock.	 
	
7.	How did you control the following variables?
	a.	height or angle
	Used a meter stick according to the table.	
	b.	quantity of material
	Filled the dish full each time.	
	c.	amount of moisture
	Measured 225 ml.	
	d.	surface condition
	Used only one type of sand.	
	e.	other
			
8.	How did you insure that only one variable was changed at a time?
	We carefully observed and recorded after each change.	 
			
9.	From your data, try to explain how earthquakes affect landslides in as 
much detail as possible.
	An earthquake will cause a slidable piece of material to move a certain 
amount for each jolt.	 
			
10.	How could you test your explanation?
	Repeat the investigation. Compare our explanation to others. Look into 
real landslide data.	 
			
11.	What was interesting or unexpected in the investigation? Why?
	The addition of water did not lower the angle required for the sand to 
slide.	 
		 
2.4e Components of the Force of Gravity		

2.4f Teacher Background Reading
Seismic Sea Waves
 
A seismic sea wave is created when a fault in the ocean floor moves vertically. 
The energy of the lifted or 
lowered water radiates outward as very long shallow water waves commonly (and 
erroneously) called tidal 
waves. Because these waves have nothing to do with the attraction of the Moon 
or the Sun, scientists prefer the 
Japanese word tsunami, which means wave in the harbor, or the English term 
seismic sea wave.

Most seismic sea waves, like most earthquakes, occur around the Pacific Ocean, 
but there have been great 
seismic sea waves in most regions of the Earth.

The great destructive power of these waves comes from the huge energy imparted 
to the water by fault 
movement. To equate this energy to mechanical work, we can imagine the work 
needed to lift an average volume 
of ocean water a distance (d) of 1 meter. The average depth of the ocean (h) is 
3.8 km. The average surface area 
(A) of the ocean floor moved up or down by such an event, according to seismic 
sea wave research, is 20,000 
square kilometersa 200 km x 100 km piece of seafloor about the size of New 
Jersey. The volume (V) of 
seawater lifted would then be 76,000 cubic kilometers. If we take 1.03 kg/m3 as 
the density (D) of seawater, the 
mass (m) of that seawater would be about 78 billion metric tons. To lift this 
much water by 1 m would take 7.6 x 
1014 Joules, the energy of 183 kilotons of TNT. See Master 2.4j for a complete 
quantitative analysis.

This energy radiates outward from the epicenter as a wave train of low waves, 
not as a single large wave. Each of 
these seismic sea waves has an average amplitude of 1 meter, wavelengths over 
100 km, and periods of 7-15 
minutes (for short-period tsunami) or over 40 minutes (for long-period tsunami). 
These waves travel at speeds 
between 550 and 800 kilometers per hour before encountering land.

Seismic Sea Wave Characteristics
Seismic sea waves are very different from wind-generated sea waves. Normal wind 
waves rarely have 
wavelengths over 300 meters, and generally travel under 100 km/hr. A medium-
sized tsunami can have 
wavelengths of 150 km and travel at 550800 km an hour. Tsunami are like tides 
in that a low tide is followed by 
a high tide, but in the case of a tsunami dramatic high and low tides can be 
only tens of minutes apart. This may 
be the origin of the expression tidal wave.

As seismic sea waves encounter land, they cause rapid tide-like motion. The 
trough of the waves causes very low 
tides, while the wave crests may cause a run as high as 32 meters. Sometimes 
seismic sea waves can cause 
enormous breaking waves. The mechanism for these waves is very similar to that 
of wind waves; the friction of 
the ocean bottom slows the troughs and the crests move over them and break. Thus 
the characteristics of seismic 
sea waves when they hit land, like those of wind waves, are very much related to 
the characteristics of the near-
shore ocean bottom and the shoreline.

The depth of the ocean water also controls the speed of seismic sea waves. As 
the depth changes, the waves 
speed and direction change, resulting in the phenomenon we call refractionthe 
change in direction of a wave as 
it moves from one medium to another.

Extensive international cooperation has developed a tsunami early warning system 
for the Pacific Islands. A 
system for the U.S. Pacific Coast is being developed. The older system is 
centered at the Pacific Tsunami 
Warning Center in Honolulu, where data are collected from seismic observatories 
across the globe. The Center 
evaluates the potential of a tsunami and institutes special observations at 
various tsunami watch stations. All 
these data are verified and emergency preparation procedures are put into effect 
when necessary.

Causes Other Than Earthquakes
Not all destructive sea waves are caused by earthquakes. Some are caused by 
landslides and volcanic eruptions 
and some are artificially created by events like underwater nuclear explosions. 
In 1883, the Krakatoa Island 
volcano erupted, blowing the island away down to a depth of about 43 m below sea 
level. This event caused giant 
waves that killed some 36,000 people in Java and Sumatra.

2.4g Tsunami Event Reports

1. On July 12, 1993, the Hokkaido-Nansei-Oki earthquake of magnitude 7.8 
produced one of the largest seismic 
sea waves in Japans history. The tsunami hit the Okushiri coast within five 
minutes after the main shock, 
causing waves at the shoreline between 15 and 30 m high. The town of Aonae on 
the island of Okushiri suffered 
extensive damage. At least 185 people were killed, with property damage 
estimated at $600 million.

2. The Prince William Sound, or Anchorage, Alaska, earthquake of March 27, 1964, 
caused seismic sea waves 
generated by an underwater landslide. At Valdez, the earthquake triggered a 
landslide that deepened the harbor 
by as much as 100 m in one place and caused a tremendous tsunami. In addition, 
the earthquake uplifted the sea 
floor by as much as 4 meters. The tsunami killed 119 people in Alaska, Hawaii, 
and California and caused over 
$282 million in damage.

3. On April 1, 1946, at 53.5 north and 163 west, 130 km southeast of Unimak 
Island, Alaska, a large earthquake 
occurred 4,000 m below the ocean surface in the Aleutian Trench, causing an 
undersea landslide. Four and one 
half hours later, a tsunami reached Oahu, Hawaii, after traveling 3,600 km at 
800 km/hr. Water rose 12 m above 
the high tide line on Oahu and 18 m on Hawaii (the Big Island). This seismic 
sea wave demolished 488 homes 
and damaged 936 others, with property loss estimated at $25 million and 173 
people killed.
4. An earthquake on the ocean floor may also cause a compressional wave that can 
severely damage ships close 
to the epicenter of the event. Even though we consider fluids as non-
compressional in systems like automobile 
brakes, compressional waves can travel in seawater under the tremendous 
pressures and accelerations of the 
water in underwater seismic events. Ships struck by these waves report an 
experience similar to running aground 
or striking another vessel.

In 1969, a magnitude 8.0 earthquake west of Gibraltar caused compressional waves 
that struck the 32,500-ton 
tanker Ida Knudsen, sailing in 4,900 m of water. The tanker was 35 km from the 
epicenter of the seaquake and 
suffered so much damage that at first it was declared a total loss. The ship was 
later extensively rebuilt.

2.4h Seismic Sea Waves
Activity Sheet

Name
Date
Characteristics of a Seismic Sea Wave
Label the following characteristics and state the average values.
 
A Possible Tsunami Scenario
Imagine that a magnitude 6.8 earthquake occurs 1,625 km from a coastal town on a 
strike-slip fault in the ocean 
floor, where the water is 3.8 km deep. A wave train is generated with a speed of 
650 km/hr and wavelengths of 
150 km. The National Tsunami Warning Center alerts the townspeople.

1. How long will it take the tsunami to hit the coastal town?

2. The first wave hits at 2:00 p.m. Does Jen have time to rescue the boom box 
left on the beach before the next 
wave hits? Calculate the period of the waves. (Period is wavelength divided by 
speed.)

3. Describe what might happen when this seismic wave encounters the coastal 
town.

4. What could be done to prepare for this tsunami?

2.4h Seismic Sea Waves
Activity Sheet (key)

Characteristics of a Seismic Sea Wave
Label the following characteristics and state the average values.

A Possible Tsunami Scenario
Imagine that a magnitude 6.8 earthquake occurs 1,625 km from a coastal town on a 
strike-slip fault in the ocean 
floor, where the water is 3.8 km deep. A wave train is generated with a speed of 
650 km/hr and wavelengths of 
150 km. The National Tsunami Warning Center alerts the townspeople.

1. How long will it take the tsunami to hit the coastal town?
Time = Distance / Speed =	1,625 km = 2.5 hours
	650 km / hr

2. The first wave hits at 2:00 p.m. Does Jen have time to rescue the boom box 
left on the beach before the next 
wave hits? Calculate the period of the waves. (Period is wavelength divided by 
speed.)
Period = Wavelength / Speed =	150 km = .23 x 60 = 13.8 min
	650 km / hr

3. Describe what might happen when this seismic wave encounters the coastal 
town.
There would be very high and very low water with only minutes in between.

4. What could be done to prepare for this tsunami?
People could be warned to move to high ground.

2.4i Wave Characteristics and Energy
 
2.4j Seismic Sea Waves
Energy Analysis
 
Name
Date

To calculate the minimum energy needed to cause an average seismic sea wave, we 
can calculate the work 
needed to give a particular volume of ocean water some gravitational potential 
energy. In essence, this means 
calculating the product of the force needed to lift a particular volume of water 
and the height to which it is lifted. 
Using the average values from tsunami research to carry out the following steps, 
calculate the energy released 
by an earthquake on the sea floor that starts a seismic sea wave.

1. What is the average sea floor area that moves in an earthquake that results 
in a seismic sea wave?

2. Knowing that the average ocean depth (h) is 3.8 km, what volume (V) of water 
is moved in the disturbance that 
causes a seismic sea wave? (Use the formula V = Ah.)

3. This volume of ocean water has a certain mass. Knowing the density (D) of 
ocean water to be 1.03 kg/m3, 
calculate the mass (m) of the water moved by the quake. (Use the formula m = 
DV.)
(note: 1 km3 = 1 x 109 m3)

4. To lift that mass of ocean water requires a force that is at least equal to 
waters weight. Using 9.8 m/s2 as the 
acceleration due to gravity (g), calculate the force (F) needed to lift that 
much ocean water.

5. Supposing that volume of ocean water is lifted an average height (d) of one 
meter, how much work (W) is 
done? This value represents the energy imparted to the seismic sea wave by the 
earthquake.

6. How much energy is this in equivalent tons of TNT? 1 Ton TNT = 4.18 x 109 
Joules

7. Imagine this much energy spreading over a great area, but then being applied 
to say only 3.8 meters of water 
instead of 3.8 kilometers. How high might the 3.8 meters of water be lifted?

2.4j Seismic Sea Waves
Energy Analysis (key)

1. What is the average sea floor area that moves in an earthquake that results 
in a seismic sea wave?

A = 20,000 km2

2. Knowing that the average ocean depth (h) is 3.8 km, what volume (V) of water 
is moved in the disturbance that 
causes a seismic sea wave?

Volume of seawater: V = Ah = (20,000 km2)(3.8 km) = 7.6 x 104 km3
= 76,000 km

3. This volume of ocean water has a certain mass. Knowing the density (D) of 
ocean water to be 1.03 kg/m3, 
calculate the mass (m) of the water moved by the quake. To convert km3 to m3, 
multiply by 10 m3/km3.

Density of seawater: D = 1.03 x 103 kg/m3
Mass of seawater lifted:
m = DV = (1.03 x 103 kg/m3)(7.6 x 104 km3) = (1.03 x 103 kg/m3) (7.6 x 104 km3) 
(109 m3/km3)
7.8 x 1016 kg or 78 trillion metric tons
(note: 1 km3 = 1 x 109m3)

4. To lift that mass of ocean water requires a force that is at least equal to 
waters weight. Using 9.8 ms2 as the 
acceleration due to gravity (g), calculate the force (F) needed to lift that 
much ocean water.

Acceleration due to gravity: g = 9.8 m/s2
Force due to gravity or weight of seawater:
F = mg = (7.8 x 1016 kg)(9.8 m/s2) = 7.6 x 1017 Newtons

5. Supposing that volume of ocean water is lifted an average height (d) of one 
meter, how much work (W) is 
done? This value represents the energy imparted to the seismic sea wave by the 
earthquake.

Distance lifted: d = 1 m
Work done against gravity:
W = Fd = (7.6 x 1017N)(1 m) = 7.6 x 1017 Joules.

6. How much energy is this in equivalent tons of TNT?

Conversion factor: 4.18 x 109 Joules = 1 Ton TNT
W = Energy = (7.6 x 1017 Joules) (1 Ton TNT/4.18 x 109 Joules)
Energy = 1.8 x 108 Tons TNT or 180 Megatons TNT

7. Imagine this much energy spreading over a great area, but then being applied 
to say only 3.8 meters of water 
instead of 3.8 kilometers. How high might the 3.8 meters of water be lifted?

If all the energy were applied to only 3.8 meters of water (1/1,000th), then the 
water would rise 1,000 meters 
instead of only one meter. The energy spreads out very rapidly, so maybe only 
1/100th of the energy reaches the 
3.8 meters of water. In this case the water would rise 30 metersquite a 
sizeable wave.

2.4k Seismic Sea Wave Research and Report Form

Name

Date

Event

Cause

Characteristics of the tsunami

Damage

What could have been done to prevent the damage?

Information Source 
Title:
Author: 
Publisher and place of publication:
Date:

2.4j Grading Matrix

Score 4 points 
Students clearly communicate all the facts about their event, covering each of 
the categories on the Seismic Sea 
Wave Research and Report Form. While reporting the waves characteristics and 
energy, students connect the 
Wave Characteristics and Effects activity sheet and the Energy Analysis activity 
to their event. The students 
employ logical thought processes and a knowledge of todays safety practices in 
their discussion of damage 
prevention. They use some visual method of communicating their ideas, such as 
the board, an overhead, a video, 
a poster, or a demonstration.

Score 3 points 
Students clearly communicate all the facts about their event, covering each of 
the categories on the Seismic Sea 
Wave Research and Report Form. They do not effectively connect the Wave 
Characteristics and Effects activity 
sheet and the Energy Analysis activity to their event. The students discussion 
of preventive measures is good. 
They use the board, an overhead, a video, a poster, or a demonstration in their 
report.

Score 2 points 
Students clearly communicate all the facts about their event, covering each of 
the categories on the Seismic Sea 
Wave Research and Report Form. They superficially mention wave characteristics, 
wave energy, and preventive 
measures, or they cover one of these three, but not the others. They rely mainly 
on the spoken word to 
communicate their information and ideas.

Score 1 point 
Students report the facts of their event by reading directly from the Seismic 
Sea Wave Research and Report 
Form. They hardly mention wave characteristics and energy. The discussion of 
preventive measures, if any, is 
incomplete. They do not use any visual communication aides.

Score 0 points 
Students report incorrect information. The Seismic Sea Wave Research and Report 
Form was poorly completed 
and the presentation to the class is poor. Statements about the waves 
characteristics, its energy, and damage 
prevention are missing or inaccurate.

2.5 Quake-Smart Siting

RATIONALE
City planners, developers, builders, and buyers need information 
about soil and subsoil geology in order to choose sites and design 
structures that will best withstand ground shaking and other 
earthquake hazards.

FOCUS QUESTIONS
What are the important geologic considerations when choosing a 
building site and designing or reinforcing a building for earthquake 
survivability?
Have these considerations been taken into account in the planning of 
towns and cities?

OBJECTIVES
Students will:
1. Interpret soil- and earthquake-related geologic maps.
2. Apply these interpretations in choosing a building site and an 
earthquake-resistant building design.
3. Locate information about the soils and geology of their local 
community and apply the same process to interpret it.

TEACHING CLUES AND CUES
Sample maps are provided so students can do this activity without any 
special preparation. However, the activity will be most meaningful to students 
if they can 
relate it to their own area. Master 2.5b, Soil and Geologic Maps and 
Map Sources, suggests types of maps that would be appropriate and 
where to get them. The Unit 1 resource list suggests many other. 
sources. if you have trouble locating maps, call your county or state 
geology office or the USDA Soil Service and ask for help.

MATERIALS
 Student copies of Master 2.5a, Background Reading: Site Characteristics
 Unit 1 Resource List
 Master 2.5b, Soil and Geologic Maps and Map Sources
 Student copies of Master 2.5c, Surface Map, Soil Map, Geologic 
Map, and Hazard Map (4 pages)
 Transparencies made from Master 2.5c, Surface Map, Soil Map, 
 Geologic Map, and Hazard Map (4 pages)
 Overhead projector
 Local map prepared in Unit 1

VOCABULARY
Fault: a break or fracture in Earths crust along which movement 
has taken place.

Landfill: a site where soil has been deposited by artificial meansoften, 
where garbage or rubbish has been disposed of, then covered with dirt 
and compacted.

Landslide: an abrupt movement of soil and bedrock downhill in 
response to gravity. Landslides can be triggered by an earthquake or 
other natural causes.

Liquefaction: the process in which a solid (soil) takes on the 
characteristics of a liquid as a result of an increase in pore pressure and 
a reduction in stress.

Sedimentary deposits: accumulation of solid particles that originated 
from the weathering of rocks and that have been transported or deposited 
by wind, water, and ice.

Seismic: of or having to do with earthquakes.

Slump: a type of landslide in which a block of rock or soil moves along a 
curved surface and rotates.

Tsunami: a potentially destructive ocean wave created by an 
earthquake or other large-scale disturbance of the ocean floor; a 
seismic sea wave. This Japanese word has the same form in both the 
singular and the plural.

PROCEDURE
Teacher Preparation (optional but highly recommended)
If at all possible, gather a selection of local geologic and soil maps in 
advance. Make student copies of these maps or the appropriate 
portions of them. If you are not familiar with maps of this type, invite a 
local geologist or soil scientist to explain them.

A. Introduction
Have students read Master 2.5a, Background Reading: Site 
Characteristics, as homework, or read it with them in class. Explain 
and amplify any unfamiliar terms. Discuss the relationship between 
soils, subsoil geology, and the suitability of a site for building. Explain 
that the locations of roads, utility lines, reservoirs, and other facilities 
also involve seismic considerations.

B. Lesson Development
1. Divide students into small groups. Give each group one copy of 
Master 2.5c, Surface Map, Soil Map, Geologic Map, and Hazard Map 
(4 pages). Use the map keys to review the special symbols and 
markings on each map. Instruct students to interpret the information 
shown on the specialized maps and transfer it to the surface map.

2. As a class, discuss what type of building would be most earthquake 
resistant in each area of the maps the groups have developed. Ask: Are 
there some areas where construction is not advisable no matter what 
the building materials? Instruct students to add these notations to the 
maps.

3. When all the maps have been completed, site hazards have been 
noted, and construction recommendations have been made, regroup 
students into three or four large groups. Within each large group, stu-
dents can quiz each other about the potential of various sites on their 
maps.

4. Ask for a volunteer from each large group to report on the groups 
findings and recommendations. Ask students: What would be the best 
way to share your recommendations if these maps represented your 
own area of the country?

C. Conclusion
Stack the three specialized maps on the projector at the same time so 
the various kinds of information are all displayed simultaneously. 
Discuss the conclusions that students have drawn and answer any 
questions. Extend the discussion to the geologic history and hazard 
potential of your own region.

(optional but highly recommended) 
Direct students attention to the local map they prepared in Unit 1. 
Have them follow the process they used above to transfer information 
from local soil maps to the classroom map, noting any implications for 
building and the location of critical facilities. If this process arouses 
concerns about safety during an earthquake, ask students to contact the 
local officials they interviewed in Unit 1 to express their concerns and 
find out if these concerns have been taken into consideration. Ask 
these students to report back to the class on what they learn.

2.5a Teacher Background Reading
Site Characteristics

Earthquakes dont kill people, buildings do.
Architects and engineers consider this a fair one-sentence summary of 
earthquake-related deaths, injuries, and 
damage. Yet, underneath every building is the Earth, which can shake and damage 
or destroy the building. In the 
final analysis, the cause of the death and destruction may not be the earthquake 
or the building, but rather 
someones lack of knowledge about the soil and subsoil under the building. Much 
of the scientific study 
surrounding earthquakes is focused on the geological characteristics of building 
sites, the relationship of building 
sites to earthquake damage, and how buildings respond to ground shaking induced 
by earthquakes. Location is 
just as important as building design for making sure that a building can survive 
an earthquake. Geological site 
considerations include the location and history of faults, sedimentary deposits, 
landfill, liquefaction, steep slopes 
and landslides, tsunami, and human-made hazards.

Faults: Displacement and Ground Shaking
Earthquakes happen when two sides of a fault are displaced, releasing energy in 
waves. Buildings can be 
damaged either by direct displacement on the fault or by ground shaking.

Geologists have mapped the locations of many of the most dangerous fault zones 
in the U.S., yet many faults are 
not yet recognized. A building within a fault zone can be severely damaged by an 
earthquake on that fault, but 
this kind of damage is rare. Most buildings are not in fault zones, and the 
recurrence interval for any particular 
fault may be hundreds or thousands of years. The most common cause of damage in 
earthquakes is the ground 
shaking caused by the earthquake waves. These attenuate, or die off, with 
distance, so the two most important 
factors controlling the amount of shaking are the magnitude of the earthquake 
and the distance of the building 
from the fault.

The distance from the fault, not from the epicenter, determines the amount of 
damage. Energy is produced by all 
the parts of the fault that move in an earthquake. Because in big earthquakes 
the fault can be hundreds of miles 
long, a structure may be hundreds of miles from the epicenter and still be on 
top of the quakes impact zone.

Several other factors can affect the amount of shaking. Waves do not travel 
evenly in all directions from the fault, 
so the orientation of the fault and the way in which displacement on the fault 
occurs can change the 
characteristics of the waves. Even more important are variations in local 
topographythe lay of the land
including the subsoil layers, which may trap or amplify seismic energy, and the 
type of rock and soil that underlie 
buildings.

Sediments and Landfill
Ground shaking is greatest on soil that has arrived in place fairly recently, 
whether it was put there by natural 
processes (in which case, geologists call it sediment) or by artificial ones (in 
which case, it is called landfill). 
Unfortunately, most of the worlds urban centers are sited on relatively young, 
loose, sedimentary deposits. 
Sediment age and particle size are important in predicting how soil will respond 
to shaking during an earthquake. 
Areas near the shores of rivers and oceans are especially likely to contain 
young sediments washed there by the 
water.

Structures located on former watercourses (such as old river beds) or on sites 
that have been artificially filled 
with sand dredged up from the bottom of a body of water are among the worst 
locations for construction in 
earthquake country because the soil can shift so easily. In Mexicos devastating 
1985 earthquake, Mexico City, 
320 km (200 miles) from the epicenter, suffered far more damage than the 
shoreline towns closer to the epicenter. 
The shoreline is made of solid rock, but Mexico City is built on the sediments 
of an ancient lakebed.

Old watercourses are usually low and wet, so they are frequently filled when 
someone wants new land to build on 
and sell. Landfill is usually a mixture of soil, rock, and decaying organic 
material in particles of varying sizes.

Because it is not natural to the area where it has been put, landfill in one 
spot is likely to be of a different 
composition from landfill in another spot nearby. When seismic waves are 
transmitted through landfill, they are 
amplified and their period is lengthened. Long earthquake waves are particularly 
destructive to some types of 
surface structures. Landfills commonly will settle and sink during a strong 
earthquake.

Liquefaction
Whenever poorly consolidated soil or fine sand becomes saturated, an earthquake 
is likely to cause soil 
liquefaction. Earthquake vibrations compact the soil, causing water mixed with 
sand to flow upward. Structures 
may settle several feet or even topple, causing considerable damage. In a 
related phenomenon, sandy or muddy 
soils may behave like liquids, flowing out onto the surface as sand boils or mud 
boils.

Slopes and Landslides
Structures on cliffs and ridges are also at high risk for earthquake damage, 
even if they are built on strong 
bedrock. Earthquake waves appear to be reflected and amplified by topographic 
highs like cliffs and ridges. 
Earthquakes also dramatically increase the potential for landslides in areas 
where landslides are common, such as 
those where sedimentary rocks lie just under the soil. The probability of an 
earthquake-related landslide depends 
on the strength of the slope materials, the steepness of the slope, and the 
extent and duration of ground shaking. 
Structures on cliffs and ridges need to be designed to the highest earthquake 
standards, and should be fully 
insured.

Tsunami
Tsunami are caused by faulting and the abrupt movement of the ocean floor during 
an underwater earthquake. A 
wave generated by this movement can travel as fast as 640 km/hr (400 mph) on the 
open ocean, where it may not 
be much above normal height. When it approaches the shore, however, it may 
attain a height of 15-20 m (50 
feet)in some cases, even 32 m. Tsunami present a distinct hazard to low-lying 
coastal areas, particularly the 
west and northwest shorelines along the western North American coast and the 
northerly facing coast of Hawaii. 
Low-lying waterfront properties in these areas are at high risk from tsunami.

Human-Made Structures
Human-made structures, such as dams, reservoirs, water tanks, and tall 
buildings, can present special earthquake 
hazards, and need to be considered during site selection. Every building 
decision needs to consider the exposure 
to geologic hazard and the probability of an earthquake, bearing in mind that 
earthquakes are possible anywhere 
in the world at any time.

2.5b Soil and Geologic Maps and Map Sources

 USGS topographical maps of your area

 Detailed USGS seismic maps that specifically identify earthquake fault traces 
(available only for areas of high 
seismic risk)

 Maps issued by state departments of geology or natural resources

 Land use policy or development maps, available from county or city zoning 
offices. The use of these maps is 
mandatory for all nonresidential and large-scale residential construction. They 
may be referred to as special 
studies zones maps

 Seismic risk maps. These are based on the location, number, and magnitude of 
historic earthquake events that 
have taken place and been recorded during the last 200 years

 Maps indicating areas of structurally defective grounds, generally developed 
by state or local agencies to 
include (a) poor soils and (b) landslide areas

 Landslide susceptibility maps, available from USGS for specific regions in the 
U.S. The U.S. Department of 
Housing and Urban Development also has data and maps of landslide problems.

 Maps noting geologic hazards; may he included in your local building codes

 Microzonation maps include data on the anticipated maximum earthquake 
intensity, active faults, geologic 
units, special studies zones, ground response, liquefaction susceptibility, 
landslide susceptibility, and zones of 
potential tsunami inundation. Available from zoning offices.

 Soil studies of the area produced for agricultural purposes, either by USDA or 
local agencies

 Soil maps produced by the Soil Conservation Service

BOOKS FOR YOUNG READERS
Asimov, I. (1978). How Did We Find Out about 
Earthquakes? New York: Walker.

Aylesworth, T.G., and Aylesworth, V.L. (1983). 
Moving ContinentsOur Changing Earth. Hillside, 
N.J.: Enslow.

Eicher, D.L. (1976). Geologic Time. Englewood 
Cliffs, NJ. Prentice Hall.

Eicher, D.L. (1984). The History of the Earths Crust. 
Englewood Cliffs, NJ: Prentice Hall.

Fodor, R.V. (1978). Earth in Motion: The Concept of 
Plate Tectonics. New York: William Morrow.

Iacopi, R. (1974). Earthquake Country. Menlo Park, 
CA: Lane Book Company.

National Geographic Society. (1982). Our Violent 
Earth. Washington, DC: National Geographic Society.

Poynter, M. (1990). Earthquakes: Looking for 
Answers. Hillside, NJ: Enslow.

Walker, B. (1981). Earthquake. (Planet Earth series) 
Alexandria, VA: Time-Life Books.

BOOKS
Adams, M. W., editor. (1970). Tsunamis in the Pacific 
Ocean. Honolulu, HI: East-West Center Press.

Bolt, Bruce A. (1993). Earthquakes. New York: W. H. 
Freeman and Co. General information on earthquakes 
in a readable style. Probably the best single source 
currently available.

Bolt, Bruce, A. (1982). Inside the Earth. San 
Francisco: W.H. Freeman and Co. More technical than 
the later Earthquakes, but highly readable for adults 
and advanced students. Includes excellent historical 
information; portraits of Beno Gutenberg, Inge 
Lehmann, and other pioneers of seismology; plus 
challenging activities and exercises.

Bonini, W.E., and Bonini, R.R. (1986). Andrija 
Mohorovicic: Seventy Years Ago an Earthquake 
Shook Zagreb. In History of Geophysics, Vol. 2, 
edited by C. Stewart Gillmor. Washington, DC: 
American Geophysical Union, pp. 83-88.

Earthquake National Research Council. (1986). Active 
Tectonics. Washington, DC: National Academy Press. 
An anthology of technical discussions, part of the 
Studies in Geophysics series.

Eiby, G.A. (1980). Earthquakes. Auckland, New 
Zealand: Heineman.

Georgi, Johannes. (1934). Mid-Ice: The Story of the 
Wegener Expedition to Greenland. London, England: 
K. Paul, Trench, Trubner, and Co., Ltd.

Gere, J.M., and Shah, H.C. Terra Non Firma: 
Understanding and Preparing for Earthquakes. New 
York: W.H. Freeman.

Gubbins, David. (1990). Seismology and Plate 
Tectonics. New York: Cambridge University Press. An 
undergraduate textbook. Readable, with useful 
illustrations, many advanced math activities, and some 
60 seismograms.

Levin, H.L. (1978). The Earth through Time. 
Philadelphia, PA: W.B. Saunders.

Moore, Gwendolyn B., and Yin, Robert K., 
(November 1984). Innovations in Earthquake and 
Natural Hazards Research: Determining Soil 
Liquefaction Potential. Washington DC: Cosmos 
Corporation (202-728-3939).

Nance, John J. (1989). On Shaky Ground: Americas 
Earthquake Alert. New York: Avon Books.

National Academy of Sciences. (1985). Liquefaction 
of Soils during Earthquakes. Washington, DC: 
National Academy Press.

Federal Emergency Management Agency/National 
Science Teachers Association (NSTA)/FEMA. 
(1988). EarthquakesA Teachers Package for K-6. 
FEMA 159. Washington, DC: FEMA Publications 
(500 C St. SW, Washington, DC 20742).

Oakeshott, G.B. (1976). Volcanoes and Earthquakes: 
Geologic Violence. New York: McGraw Hill.

Pakiser, Louis. (1989). Earthquakes. Washington, DC: 
U.S. Government Printing Office. An illustrated 
pamphlet of general information, prepared for the U.S. 
Geological Survey, Department of the Interior.

Scholtz, Christopher H. (1990) The Mechanics of 
Earthquakes and Faulting. Cambridge, England: 
Cambridge University Press. A technical reference for 
teachers interested in exploring further.

U.S. Department of Commerce, Coast and Geodetic 
Survey. (1965). Tsunami! The Story of the Seismic Sea 
Wave Warning System. Washington, DC: U.S. 
Government Printing Office. An exciting story with 
fine illustrations, at a students reading level.

Wegener, Alfred (1966). The Origin of Continents and 
Oceans. New York: Dover.

Wegener, Else. (1939). Greenland Journey: The Story 
of Wegeners German Expedition to Greenland in 
1930-1931. London and Glasgow: Blackie and Son 
Ltd.

ARTICLES AND PAPERS
Evaluating Earthquake Hazards in the Los Angeles 
RegionAn Earth Science Perspective. U.S. Geologic 
Survey Professional Paper #1360, 1985, pages 
375-413, Evaluating Tsunami Potential.

Gore, R. (1985). Our Restless Planet Earth. National 
Geographic 168: 142-181. Includes map, Earths 
Dynamic Crust.

Lowman, P.; Wilkes, Y,; and Ridky, R.W. (1978). 
Earthquakes and Plate Boundaries. Journal of 
Geological Education 26: 69-72.

Matthews, Samuel, W. (1973) This changing Earth. 
National Geographic 143: 1-37.

McCredie, Scott. (March 1994). Tsunami: The Wrath 
of Poseidon. Smithsonian Magazine 24, 12:28-39.

Peterson, Ivars. (Oct. 12, 1985). Liquid Sand. 
Science News.

U. S. Geological Survey, 904 National Center, Reston, 
Virginia, 22092; 703/648-6078. See especially 
Pacific Tsunami Warning System, Volume 18, 
Number 3, 1986, and Devastating Tsunami Inspires 
Efforts to Reduce Future Tsunami Destruction, 
Volume 19, Number 2, 1987.

Wilson, J.T., ed. (1970). Continents Adrift: Readings 
from Scientific American. New York: W.H. Freeman 
and Co.

NONPRINT MEDIA
California Earthquake Education Project. Earthquake 
kits and group materials. Lawrence Hall of Science, 
University of California, Berkeley, CA 94720; 
415/327-6017.

The Drift Globe. Burlington, NC: Omni Resources, 
Inc. (919/227-8300). A 12"-diameter globe with velcro 
fasteners and velcro continents. Instruction guide is 
illustrated with cartoons.

The Earthquake Connection. A live-action video in 
two parts. Available from Wards Natural Science 
Establishment, Inc., 5100 W. Henrietta Road, PO Box 
92912, Rochester, NY; 800-962-2660. Wards also has 
earthquake filmstrips and slides.

Earthquake Effects: A Computer Animation and Paper 
Model. U.S. Geological Survey Open-File Report 
92-200B, by Tau Rho Alpha, Robert A. Page, and 
Leslie C. Gordon. Order from U.S. Geological Survey, 
PO Box 25425, Denver, CO 80225; 303-236-4476.

Earthquake Simulator. A program for the Apple II 
series. Available from Wards Natural Science 
Establishment, Inc., 5100 W. Henrietta Road, PO Box 
92912, Rochester, NY; 800-962-2660.

Earthquake Slides. Photographs of earthquake effects, 
copies of seismograms, and seismicity maps can be 
obtained from the National Geophysical and Solar 
Terrestrial Data Center, Code D62, NOAA/EDS, 
Boulder, CO 80302.

Earthquake Sounds. A cassette tape of sounds 
recorded in various earthquakes, available with a 
catalog from Seismological Society of America, 201 
Plaza Professional Building, El Cerrito, CA 94530; 
415-525-5474.

Earthquakes: Environments and Effects. A 15-minute 
interactive videotape available from CALEEP, 510-
642-8718.

EERI Videotapes and Slide Sets. Oakland, CA: 
Earthquake Engineering Research Institute. For 
information, phone 510-451-0905, or fax 510-451-
5411.

Steinbrugge Collection. Richmond, CA: Earthquake 
Engineering Research Center. Over 10,000 
photographs and 5,000 slides of earthquake damage. 
The library will provide copies to teachers and 
researchers. Call 510-231-9401 for information.

Note: Many of the references for Unit 3 may also be useful 
for teaching this unit. Inclusion of materials in these 
resource listings does not constitute an endorsement by 
AGU or FEMA.