Nicole McMahon
ndmcmaho@mtu.edu
Title: Earthquake Measurement Scales
Drawings:
P-Wave
S-Wave
Surface Waves
Amplitude
Source: http://rev.seis.sc.edu/index.html
Earthquake: 9/29/2009, Samoa Islands Region, ML 7.9, MW 8.0
Source:
http://upload.wikimedia.org/wikipe
dia/commons/8/81/2008-IwateEarthquake-Intensity.jpg
Objective: To introduce the different scales used to describe the size of earthquakes
Materials needed:
8.5x11 Paper (1 for each two students)
Pencils (1 for each student)
Prepared questions for EQ drill and Trivia Challenge
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Nicole McMahon
ndmcmaho@mtu.edu
Time duration: 40 minutes
Vocabulary:
Intensity – A measure of the violence of an earthquake in terms of the extent to which people felt
the earthquake, the damage to structures, and secondary effects such as landslides.
Several intensities can be assigned for a single earthquake.
Magnitude – A measure of earthquake size that corresponds to the energy release during the
earthquake. Only one magnitude is assigned to a single earthquake.
Modified Mercalli Intensity Scale – An arbitrary scale of earthquake intensity devised in 1902 by
Guiseppi Mercalli based on earthquake effects. Numbers (Roman numerals) range from I
(earthquake felt only by seismometers) to XII (total destruction).
Moment Magnitude Scale – A numerical scale of earthquake magnitude devised by
seismologists. Numbers vary between 0 and 10 are calculated based on physical
parameter “seismic moment” (area of the fault plane*displacement on the fault
plane*rock strength). Magnitudes represent energy release.
Richter Magnitude Scale – A numerical scale of earthquake magnitude devised in 1935 by the
seismologist Charles Richter. Numbers vary between 0 and 10 and are calculated based
on the maximum wave amplitude on a specific seismometer.
Seismogram – The record made by the seismometer.
Seismometer/Seismograph – An instrument that records seismic waves (i.e. from an earthquake).
Activities:
1. Introduction: Japanese Earthquake Drill (5m)
Explain to the students that in Japan (California, as well), routine earthquake drills are
performed in the same way we do fire drills. Explain that when shaking is felt, students
immediately climb underneath their desks to prevent debris from falling on their heads.
Activity:
Do one practice drill and explain to students that several times throughout the class you
are going to give an inconspicuous signal (such as touching your ear/nose) which means
the ground has started shaking and they are to get under their desk immediately. The last
person to get down will have to answer a trivia question. Questions could be based on
teaching material or fascinating earthquake facts (largest earthquake, most seismically
active state etc.)
2. Introduction: Human Seismometer (10m)
Briefly explain to students the basics of seismometers (maybe drawing examples on the
board) and explain that the Richter Scale measures the magnitude of earthquakes.
Activity:
Have students pair up with one sheet of paper and two pencils. Have students draw two
blank seismograms on their sheet of paper. One student will be the seismometer, holding
the pencil very lightly above the zero amplitude line and slowly pulling forward in time.
The other student will act as the earthquake shaking the desk (starting small and growing
in magnitude). Place the extra pencil at the edge of the desk (part hanging off), and have
the students shake until the pencil falls off. The amplitude at the point the pencil falls off
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Nicole McMahon
ndmcmaho@mtu.edu
will be the put into this equation (ML=3A) to determine the magnitude of the earthquake.
Actual equation:
M L  log 10 A  log 10 A0 ( D)
Where A=amplitude of EQ (in mm), A0=background amplitude, and D is distance from
epicenter.
Debriefing:
Explain that one number increase in magnitude is equal to 10x seismic wave amplitude
increase and 32x energy increase ((M5-M7, 100x amplitude, 1024 energy).
Richter scale is outdated and moment magnitude is used which is (area of fault plane x
displacement x rock strength) and measures actual energy release better.
<M4 – small earthquakes, rarely cause significant damage
M5-M7 – large earthquakes, can cause significant damage
>M8 – Catastrophic
Can use the board to write down a few numbers and effects.
3. Introduction: Earthquake Intensity Scale (10m)
Briefly explain the basics behind the Modified Mercalli Intensity Scale (using board for
illustration) and maybe show a picture.
Activity:
Have a volunteer come to the front of the room and wave a piece of paper in a big wave
toward the students. Then have students who felt the wind raise their hand, students who
didn’t, and have students guess the intensity (maybe showing the intensity map on the
board.
Debriefing:
I – Not felt
IV – Felt indoors by many, outdoors by few; dishes, windows, doors disturbed
VIII – Considerable damage to ordinary buildings (slight damage to specially-designed
structures); many chimneys fall and heavy furniture overturned
XI – Few to no masonry structures standing; bridges destroyed and rails bent greatly
XII – Total damage; lines of sight and levels distorted; objects thrown into the air
Can use the board to write down a few numbers and effects.
Assessment/Evaluation:
Boys vs. Girls Trivia Challenge (10m)
Have the students split into two teams (boys vs. girls) and do a trivia challenge awarding
points to the team who answers correctly.
Hangman (5m)
The teacher or the students can draw a hangman game on the board based on the vocabulary
of the material.
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Nicole McMahon
ndmcmaho@mtu.edu
Resources:
Smith, G.A. and Pun, A., 2006. How Does Earth Work? Pearson Prentice Hall: Upper Saddle
River, NJ.
Bates, R.L. and Jackson, J.A. (ed), 1984. Dictionary of Geological Terms (3ed). Anchor Books:
New York.
Wikipedia
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