quake quest

7/21/2019 Quake Quest

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TopicEarthquakes

Key Question

How can you locate the epicenter of an earthquake?

Learning GoalsStudents will:• read simplified seismograms;• read and interpret a Richter Nomogram; and• interpret data to locate the epicenter of earthquakes

using triangulation.

Guiding DocumentsProject 2061 Benchmarks • Some changes in the earth’s surface are abrupt

(such as earthquakes and volcanic eruptions)while other changes happen very slowly (such asuplifting and wearing down mountains).

• Graphs can show a variety of possible relation- ships between two variables.

NRC Standards • Lithospheric plates on the scales of continents and

oceans constantly move at rates of centimetersper year in response to movements in the mantle.Major geological events, such as earthquakes,volcanic eruptions, and mountain building, resultfrom these plate motions.

• Mathematics is important in all aspects of scientificinquiry.

• Technology used to gather data enhances accuracyand allows scientists to analyze and quantify resultsof investigations.

NCTM Standards 2000* • Recognize and apply geometric ideas and relation-

ships in areas outside the mathematics classroom,

such as art, science, and everyday life • Select and apply techniques and tools to accuratelyfind length, area, volume, and angle measures toappropriate levels of precision

MathMeasurement length

ScienceEarth science geology

Integrated ProcessesObservingInferringCollecting and recording dataInterpreting dataDrawing conclusions

MaterialsFor each group:

one pushpin two scale compass cards (see Management 5) pencil with a sharp point one 12-inch by 18-inch piece of cardboard

Background Information The study of earthquakes is called seismology.Earthquakes occur as a result of a sudden release ofstored energy. This energy builds up over long peri-ods of time as a result of forces between the Earth’stectonic plates. Most earthquakes occur along faultsin the upper part of the Earth’s crust when one tec-tonic plate moves rapidly relative to the position ofthe other plate. This sudden motion causes seismicwaves to radiate out. This area is called the focus.

A seismic wave transfers energy from one spotto another within the Earth. There are two types ofwaves that scientists monitor during earthquakes: P(primary) waves, which are similar to sound waves,and S (secondary) waves which are a type of shearwave. In the Earth, P waves can travel through solidsand liquids; S waves can travel only through solids Seismographs are instruments used to measureEarth movement. The first seismograph was cre-ated in the second century AD in China. The brilliant

scientist, mathematician, and inventor Chang Hengdeveloped this seismograph. The illustration on thestudent map page of this activity shows what thisseismograph looked like. A tremor caused one ofeight bronze balls that were placed in the dragon’smouth to drop into the mouth of one of eight bronzefrogs. The path of the ball indicated the area fromwhich the tremor came.

EARTH BOOK 109 © 2007 AIMS Education Foundatio



Modern seismographs began their development in1848. The principle behind a traditional seismographis rather simple. A weight is freely suspended from asupport that is attached to bedrock. When waves froma distant earthquake reach the instrument, the inertiaof the weight keeps it stationary, while the Earth andthe support vibrate. The movement of the Earth in rela-tion to the stationary weight is recorded on a rotatingdrum. It produces a seismogram that shows a continu-ous record of Earth movement. There are seismographicstations all over the world. There are literally millions ofearthquakes that can be detected by a seismographeach year. Thousands are strong enough to be felt bypeople.

Management 1. Emphasize to the students that the seismogram

in this activity is highly simplified. Use theseismogram on the student page to help thestudents identify the following parts:

• P waves and the P wave arrival time

• S waves and the S wave arrival time • S-P interval (expressed in seconds) • S wave maximum amplitude (measured in mm) The P waves are the first to arrive at a seismo-

graphic station. The S waves will follow. Thedifference in time between the arrival of the P andS waves is called the S-P interval. The amplitudeof the S wave is measured in mm and is read onthe vertical axis of the seismogram. The maxi-mum amplitude can be above or below the 0 lineon the seismogram.

2. To locate an earthquake’s epicenter, you need tohave the seismogram readings from three sites.

On each of the seismograms you will need todetermine the S-P interval. The S-P interval willthen be used to determine the distance the wavestraveled from the origin of that station.

3. The epicenter for Data Set One is in the northwestcorner of Wyoming (Yellowstone National Park)and the second epicenter is Charleston, SouthCarolina. Both of these sites are seismologicallyactive areas.

4. The map scale should measure 7 mm equals100 km. You may need to have students adjusttheir scale compass cards as a result of distortionthat occurs when items are photocopied.

ProcedurePart One 1. Ask the Key Question and state the Learn-

ing Goals. 2. Distribute the first student page with the model

seismogram. Direct the students to examine themodel seismogram. Have students locate andidentify the following parts:

• P waves and the P wave arrival time

• S waves and the S wave arrival time • S-P interval (expressed in seconds) • S wave maximum amplitude (measured in mm) • The scale intervals [The horizontal scale on

these seismograms is 2 seconds and thevertical scale 10 mm.]

3. Tell the students to determine the P-wave arrivaltime, S-wave arrival time, S-P interval in seconds,and S-wave maximum amplitude for each of thetwo examples.

4. Show the students how to use the RichterNomogram to determine the distance the earth-quake has occurred from the seismograph. Thestudents will need to first know the S-P interval.They will then use the left portion of the RichterNomogram that lists distance and S-P interval.The students will follow the vertical column ofthe S-P interval up the Richter Nomogram untilthey reach the interval in seconds that matchesthe seismogram reading. They will then read thecorresponding distance by reading horizontally

across the column. This distance is called theepicentral distance, the distance a site is fromthe epicenter of the earthquake.

5. Instruct the students how to use the RichterNomogram to estimate the magnitude of theearthquake. Direct them to plot the distance onthe left column and the amplitude on the rightcolumn. Tell them to draw a line to connect thetwo points. The magnitude can be estimatedby reading the point where the line crosses themagnitude scale in the middle. Use the RichterNomogram to estimate the magnitude of the twosample earthquakes.

EARTH BOOK 110 © 2007 AIMS Education Foundation



Part Two 1. Ask the Key Question and state the Learn-

ing Goals. 2. Distribute the maps and data sets. Determine

the P wave arrival time, S wave arrival time,S-P interval in seconds, and S wave maximumamplitude for each of the seismograms.

3. Use the Richter Nomogram to determine thedistance each station was from the earthquake’sepicenter.

4. Tell the students to tape the maps onto thecardboard.

5. Have the students construct the two scale compasscards. The students will need to use a differentscale compass card for each earthquake. Thecards are constructed from a 3 by 5 index card.Direct the students to:

• cut off two 1-cm strips from the three-inchdimension of the card;

• place the factory cut edge of each strip alongthe scale of the map and trace the map scale

onto it; • start marking the scale 2 cm from the end; • use the pushpin to place a hole on the middle

of the first line (0 km); • determine the distance from each of the

seismograms from Data Set One ; and • use the pushpin to punch a small hole

matching the three distances from the threeseismograms on the scale compass card.

6. Direct the students to use the scale compass cardto draw the three circles that go with the data set.Place the pushpin on each of the three differentcities and draw a circle using that city’s epicen-

tral distance by placing a very sharp pencil in thecorresponding hole. The earthquake’s epicenteris located at the intersection of the three circles.The students will need to make a new scalecompass card for the second data set.

7. Assist them, if necessary, in identifying thelocation of the earthquake’s epicenter.

8. Tell the students to use the Richter Nomogram toestimate the magnitude of the earthquake.

9. Ask the students what they notice about theamplitude and location of the epicenter. [Thelarger the amplitude, the closer the station is tothe epicenter.]

10. Have the students examine the second set ofseismograms. Have them predict which is theclosest station, the middle station, and the furtheststation from the epicenter. Then have them findthe epicenter of this earthquake and estimate themagnitude.

Connecting Learning1. What is the difference in a seismogram and a

seismograph? [The seismogram is the chart of anearthquake. The seismograph is the instrumentthat makes the seismogram.]

2. Why is it necessary to use three stations whenlocating an earthquake’s epicenter?

3. What do you notice about the maximum amplitudeat each seismographic station and the locationof the epicenter? [The larger the amplitude, thecloser the station is to the epicenter.]

4. Why is it important to determine the scale beforereading a graph or instrument?

5. In what part of the country do you think there are

the most seismographic stations?6. Would a fourth station reading be useful? [Itdepends on the location, a close station maygive more information on the magnitude of theearthquake.]

7. What are you wondering now?

* Reprinted with permission from Principles and Standards forSchool Mathematics, 2000 by the National Council of teachersof Mathematics. All rights reserved

SolutionsPractice

(Data approximated)S-P Interval 38 sec.Amplitude 160 mmEpicentral Distance 3600 kmEstimated Magnitude 6.5

S-P Interval 66 sec.Amplitude 100 mmEpicentral Distance 640 kmEstimated Magnitude 7.2

Data Set One (Data approximated)Cheyenne, WY

S-P Interval 64 sec.Amplitude 40 mmEpicentral Distance 620 kmEstimated Magnitude 6.7

1 c m

2 cm




Salt Lake City, UTS-P Interval 52 sec.Amplitude 90 mmEpicentral Distance 500 kmEstimated Magnitude 6.6

Helena, MTS-P Interval 33 sec.Amplitude 250 mmEpicentral Distance 310 kmEstimated Magnitude 6.5

Epicenter: Yellowstone National Park Northwest Wyoming

Data Set Two Atlanta, GA

S-P Interval 51 sec.Amplitude 150 mmEpicentral Distance 490 km

Estimated Magnitude 6.7

Raleigh, NCS-P Interval 42 sec.Amplitude 260 mmEpicentral Distance 400 kmEstimated Magnitude 6.7

Tampa, FLS-P Interval 66 sec.Amplitude 50 mmEpicentral Distance 640 kmEstimated Magnitude 6.8

Epicenter: Charleston, SC




Key Question

How can you locate theepicenter of an earthquake?

Learning Goals

• read simplifi edseismograms;

• read and interpret a RichterNomogram; and

• interpret data to locate the

epicenter of earthquakesusing triangulation.




H e l e n a , M T

S a l t L a k e C i t y , U T

C h e y e n n e , W Y

A t l a n t a , G A

R a l e i g h , N C

T a m p a , F L




✄

0 300km




1. What is the differencein a seismogram and aseismograph?

Connecting Learning

2. Why is it necessary to usethree stations when locating anearthquake’s epicenter?

3. What do you notice about themaximum amplitude at eachseismographic station and thelocation of the epicenter?

4. Why is it important to determine

the scale before reading a graphor instrument?




Connecting Learning

5. In what part of the countrydo you think there arethe most seismographic

stations?

6. Would a fourth station readingbe useful?

7. What are you wondering now?
