Name:___________________________________________________Date:___________Period:_____
Earthquakes
Epicenter-apoint,directlyabovethetruecenterofdisturbance,from
whichtheshockwavesofanearthquakeapparentlyradiate.
Define each of the following terms in your own words after watching the
video.
P-Wave:______________________________________________________________________________
S-Wave:______________________________________________________________________________
LagTime:_____________________________________________________________________________
EpicenterDistance:____________________________________________________________________
Figure1
PartA:Checkingforunderstanding
1.UsetheTimeTravelGraph(Figure2)todeterminethelagtime(inminutes)betweenthefirstP-wave
andthefirstS-Waveforthefollowingdistances.
700milesfromtheepicenter=___________minutesoflagtime
450milesfromtheepicenter=____________minutesoflagtime
2500milesfromtheepicenter=____________minutesoflagtime
2.FromtheseismographreadinginFigure1,whatwasthelagtimebetweenthefirstP-waveandthe
firstS-wave?___________________
3.RefertotheTravel-TimeGraph(Figure2).Howfaristheseismographstationfromtheepicenter
accordingtofigure1?
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Hook:Earthquakes
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PartB:Findingtheepicenter.
Figure
3
illustrates
seismograms
from
the
same
earthquake
recorded
at:
•
Sacramento,California
•
•
Columbia,SouthCarolina
Madison,Wisconsin
Usefigure3tofindthelagtimebetweenfirstP-waveandthefirstS-waveforeachlocationandthen
figure2tofindtheepicenterdistance.
Locationof
Seismograph
LagTime
EpicenterDistance
Sacramento,CA
Columbia,SC
Madison,WI
Hook:Earthquakes
2
Useyourcompasstomarkoff1800milesonthelinebelowthemap.Useacompassandthedistances
fromthe3citiestofindthelocationoftheepicenter(intersection).Usedifferentcolorstorepresenteach
city’sdistance
Hook:Earthquakes
3
Analysis:
1.Didallthreeofthecirclesdrawnwiththecompassoverlapinexactlyonespot?Whyorwhynot?
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2.Thisearthquakeoccurredclosesttowhichcity?Doesthismakesense?Explainyourreasoning.
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3.Assumethatthesameearthquakeoccurred,buttheseismicstationinSacramentomalfunctioned,
anddidnotrecordtheearthquake.Arethereanyotherlocationsthattheearthquakecouldhave
occurred?
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4.Doearthquakestravelataconstantspeed?Justifyyouranswer.
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Hook:Earthquakes
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TeacherDirections
ContentObjective:Use seismograph readings and compass to mark distances from various
cities to determine the epicenter of an earthquake.
Material:
Video:https://www.youtube.com/watch?v=3eFS4WhsrHA
Compass(1perstudent)
Straight-Edge(1perstudent)
Handout(Figure2andFigure3)1classset
ActivitySheets(1perstudent)
Directions:
Havestudentsreadquestions1–3.Givestudents2minutestothinkofanswerstoeachofthethree
questions.Dostudenttalk-strategyinsideoutsidecircle.Havestudentsstandinfrontofaclassmate.
Giveeachstudent1minutetosharetheiranswerswiththeirpartners.Thenrotatestudentssotheycan
sharetheiranswersagain.Oncecompleteditisagoodtimetogooverearthquakeproceduresandalso
whatisanepicenter.
Inside-OutsideCircleQuestions:
1.Describethelastearthquakeyouremember,whereyouwere,whowasthere,howscaredyouwere.
2.Whataretheproceduresifthereisanearthquakewhileweareinthisclass?Whatdowedoand
wheredowego?
3.Whatcausesearthquakes?
WatchYoutubevideo.Havestudentswriteinformaldefinitionsforp-wave,s-wave,lagtime,and
epicenterdistance.
PartA:
Studentscanfindthetimebyfindingthedifferenceiny-values,useapieceofpaperlikethevideo,or
useacompasstomeasurethedistancebetweencoordinates.
StudentswillneedtouseFigure2andFigure1toanswerthequestions.
1.
• 700milesabout2.5minutes
• 450milesabout1.5minutes
• 2500milesabout5.5minutes
2.About3minutes
Hook:Earthquakes
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3.800–900miles
PartB:
Theseanswersareapproximations.
Locationof
Seismograph
LagTime
EpicenterDistance
Sacramento,CA
3.8minutes
1400miles
Columbia,SC
3.2minutes
1000miles
Madison,WI
3.2minute
1000miles
Usethedistancesandacompasstofindtheepicenter.
Analysis:
1. Answerswillvary.Thelagtimewecalculatedmayhavebeenoff.
2. TheclosestcityisAustin,Tx.YesbecauseitlooksaboutthesamedistancefromColumbiaand
Madison.AlsoSacramentohadthelongestlagtimeanditisthefurthestaway.
3. IfweonlyusetwocitiesColumbiaandMadisonthentheearthquakecouldhavealsooccurredin
MainenearAugusta.
4. Answerswillvary.
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Hook:Earthquakes
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