Name__________________________________ Date__________
Earthquakes and the Modified Mercalli Scale
An earthquake is a sudden violent movement of the Earth’s crust which may cause extensive
damage and loss of life. The amount of damage caused by an earthquake depends on the intensity
of the earthquake and the distance to the epicenter. Other factors that are important are the
building materials, type of construction, and the condition of the ground. Buildings with
foundations in solid rock usually suffer less damage than those built on sand or landfills.
In this activity, you will use data from an earthquake that hit the town of Wattsville. You
will determine the Mercalli rating based on the damage reported and construct an isoseismal map
in order to find the epicenter and evaluate the damage to the surrounding area.
Problem:
How can the amount of damage caused by an earthquake be described?
How can the modified Mercalli scale be used to determine the location of an earthquake?
Vocabulary:
Earthquake ______________________________________________________________
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Epicenter _______________________________________________________________
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Modified Mercalli scale ____________________________________________________
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Richter scale _____________________________________________________________
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Isoseismal map ___________________________________________________________
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Procedure:
1. Listen to the KWAT script and determine the Modified Mercalli rating for each of the
locations in the Wattsville area by comparing the caller’s description to the modified
Mercalli scale.
2. Record the number of the modified Mercalli rating at each location on the Wattsville
map.
3. Construct an isoseismal map by drawing isoseismal lines that connect points of equal
modified Mercalli values.
Regents Earth Science 1 Mr. Clark
Bethpage HS
Name__________________________________ Date__________
Mercalli
Description
Intensity
Usually not felt except by a very few under especially favorable conditions, but detected by
I
instruments.
Felt by very few people at rest, especially on the upper floors of buildings. Delicately
II
suspended objects may swing.
Felt quite noticeably indoors, especially on the upper floors of buildings, but many people
III do not recognize it as an earthquake. Standing automobiles may rock slightly. Vibration
like a passing truck. Often mistaken for a passing vehicle. Duration estimated.
During the day, Felt indoors by many, outdoors by few. At night some awakened. Dishes,
IV windows and doors disturbed. Walls make creaking sound. Sensation like heavy truck
striking a building. Standing automobiles rocked noticeably.
Felt by nearly everyone. Many people awakened. Some dishes, windows, and so on
broken. Cracked walls with cracked plaster in a few places. Unstable objects overturned.
V
Disturbances to trees, poles, and other tall objects sometimes noticed. Pendulum clocks
may stop.
Felt by all, many frightened and many run outdoors. Some heavy furniture moves. A few
VI
instances of fallen plaster and damaged chimneys. Slight damage occurs.
Everyone runs outdoors. Damage negligible in buildings of good design and construction.
Slight to moderate damage in well built ordinary structures. Poorly built or badly designed
VII
buildings suffer severe damage. Some chimneys broken. Slight damage every where else.
Noticed by persons driving cars.
Everyone runs outdoors. Minor damage to specially designed buildings. Moderate to
considerable damage in ordinary substantial buildings, with partial collapse. Major damage
VIII
in poorly built structures. Panel walls thrown out of frame structure. Chimneys, factory
stacks, columns, monuments, and walls may collapse. Heavy furniture overturned. Sand
and mud ejected in small amounts. Changes in well water. Persons driving cars disturbed
All buildings suffer major damage. Damage considerable in specially designed structures.
Well designed frame structures thrown out of plumb. Damage great in substantial buildings
IX
with partial collapse. Buildings shifted off their foundations. Ground cracks, underground
pipes break, foundations shift.
Major damage. Structures destroyed. Ground is badly cracked. Landslides occur. Some well
built wooden structures destroyed. Most masonry and frame structures destroyed with
X
foundations. Rails bent. Landslides considerable from river banks and steep slopes. Shifted
sand and mud. Water splashed and slopped over river banks.
Almost all structures fall. Bridges wrecked. Very wide cracks in ground. Underground
XI pipelines completely out of service. Earth slumps and land slips in soft ground. Rails bent
greatly.
Total destruction. Ground surface waves seen. Objects thrown into the air. All construction
XII
destroyed. Lines of sight and level distorted.
Regents Earth Science 2 Mr. Clark
Bethpage HS
Name__________________________________ Date__________
Wattsville Map
Regents Earth Science 3 Mr. Clark
Bethpage HS
Name__________________________________ Date__________
Discussion Questions:
1. What is an earthquake? ____________________________________________________
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2. What is the modified Mercalli scale? _________________________________________
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3. What is the difference between the modified Mercalli scale and the Richter scale? ______
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4. Based on the map where is the most damage? ___________________________________
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5. Where do you think the epicenter is located? ___________________________________
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6. Why did some buildings near the epicenter sustain less damage than other buildings? ___
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7. What are some advantages of the modified Mercalli scale in rating an earthquake? _____
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8. What are some disadvantages of the modified Mercalli scale in rating an earthquake? ___
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9. How can the amount of damage caused by an earthquake be described? ______________
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10. How can the modified Mercalli scale be used to determine the epicenter of an
earthquake?
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Regents Earth Science 4 Mr. Clark
Bethpage HS