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EarlbcftlGke Information

DETERMiNING JHE TIME OF AN EARTHQUAKE

~.' ...Text Pages w.;372

&ad tilt inflJt1/llStiqn ar.d study the table givingbavel :mw of sti.sIIIk f.I1QVGfrom an 1t.I1Ihquake.1'henstvdy tilt fIIIJ/J id.mtiJJing the tpkmter of the .eart1JipuW. Usethm to answer tilt qmstions.

Seismologists use the distance from anepicenter plus the timesof the arrival ofprimary, secondary, and surface waves todetermine the time at which earthquakesbegin, .

DistanceTraveltime

from PrImary Secondary Surfaceepicenter waves waves waves

(Ian) mln see mln see mln see620 3 20 0 6 7 20

1240. 5 56 10 48 14 161860 8 00 14 30 21 302480 9 50 17 50 27 503100 11 26 20 51 35 563720 12 43 23 27 41 43

.' .; .

1. On what continent did the earthquake occur? ...::.... _

2. How far was the earthquake from London? New York? Chicago? _

3. How long did it take the primary waves to reach Chicago? _

4. The primary waves reached Chicago at 9:00 A.M. When did the earthquake occur in Chicagotime? What math operation did you use to determine the time of the earthquake?

5. The earthquake epicenter was located two time zones east of Chicago. What time was it in the

time zone containing the epicenter when the earthquake began? _

6. One seismograph station was 1860 kilometers from the earthquake's epicenter. What time was itat the seismograph station when the earthquake began if the secondary waves arrived at thestation at 6:30 A.M.? At what time would the surface waves arrive at the station?

CHAPTER-fEST . Chaplw 14.•..

EarthquakesI. Testing ConceptsCinle the term in parentMses that best completes each st{Jte7p.ent.

1. Wh~n the buildup of stress in Earth's crust is so great that rocks reach their (elastic limit,tectonic force) • an earthquake OCCIlrS-

·2. A reverse fault is often located along a (divergent, convergent) plate boundary.

3. (Primary waves, Secondary waves) move through Earth by causing particles of rocks to move ~right angles to the direction of the waves. .

4. To locate an earthquake's (epicenter, elastic limit), scientists use information from threeseismograph stations.

5. By noting the change in the speed and path of (seismic waves, Moho discontinuity)~ scientists, . nhave been able to determine the structure of Earth's interior,'···· -' .

6. Seismologists.us~the (seismograph, Richter Scale) to describe the magnitude of earthquakes. ",'

7. One way to make your home seismic safe is to put heavy items on (upper, lower) shelves.

8. The (greatest, least) loss of lite in an earthquake is caused by the destruction of structures builtby people. .

9. The San Andreas fault in California is an example of a (normal fault, strike-slip fault).

10. Most of the destruction during an earthquake is caused by (surface waves, primary waves) .

11. The radius of the circle seismologists draw on .a map is equal to the distance from a station to

an eanhquakefs (epicenter. fault line).

12. An earthquake with a (vitr"tluii, i.llagl,iuilic) of7.5 releases 3~ times as much energy a; ':'ii

earthquake that registe~ 6.5 on the Richter Scale.

13. Primary and secondary waves slow down when they hit the plasticlike (asthenosphere,

lithosphere) .

14. The area between J05° and 1400 from an earthquake's focus is called the (shadow zone,

Moho discontinuity), because no seismic waves are detected there.

15. The slowest seismic waves are (primary waves, surface waves).

16. Primary waves arrive at a seismograph station (first, second).

17. When rocks break because of stress, the energy released is in the form ofa(n) (earthquake,

tsunami).

18. The farther apart primary, secondary, and surface waves are, the (closer. farther away) theepicenter is.

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.JNFORCEMENT..;; ~ftJ ••· . ~ •... .

Earthquake Information -171,gnrIIIltthti __ ".., u- ia flillllla _ iifta."..., !."".." ".,,,a~-.-. ,ItIIII WfIIII.IIIrJ -- s/(II/.III Iitt·JllllllIiw bid dllIDIlnJoIilll ,;,. _ ••• :.t-11M grt¥IL U.w".. ••~ till fi"S1iMu 1Juit'Jlll-

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DIstaMt travlled (t00ll kill -.)

J. H6W long does it take for a prinwywave 10 tmel2000 kilomeh:n? _I

2. How long does il take for a secondary WlM: (0 \raid 2000 kilometerS? _"'-- _

3. How far datu serondarywaw: n-avelin 10 minutes? .__ ..-: ._, ,_, .. _. _

•. How fur does a primary_ u-avelin 10 minute$? ~ :.._..

S. What happens 10 the time dilTertncebetween primary and !e(ondary waves as the distance

traveled gets I~r? --'---_._-----.

Ii. SIiPTIOStISprimary and secondlry wavebodIlm'eled a di&r;an~ of 5000 kilom.eten before they1

are picked up by a r.ci.~mograph.Which wmwill arri~ fim? _~ .. __

'1. Hull' much tillle JlIg at snoo km willlbci'e be betwefllhese two ~ _

8,. Suppose bolb'a primary and I«Ondary Wile stanlogether and ~l for 5 minutes. Which wavefwill tra,~1fanher? ,;,-. ---

59

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•••••••••••••••••ActIwity 14-2. Tnldcl ••• ,..... (text page 293)

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1. Daaibc the rdI£IoDsbip betMaI tbe Iocatioo of die epicenters (tall or -.at af tile ~ i1Idthe deplh of the

~a. _

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SruDYGUIDE ChapIIr'4·

Earthquakes and Plate TectonicsOn the am abovt'Mch illv.stration, label the t'JINoff~ shown---rnmnalfault, ~ faulJ., and striltt-slipfault. Then belou1t4Ch illustration fnd the nU-Mbmoffault's cJw.racterilticsjrom the list.

1. Tension pulls rocks apart.2. Compression pushes rocks in. .3. Shearing forces push rocks from different. but not oppo-

site, directions.4. This kind of fault occurs at transform fault boundaries,S. This kind of fault occurs at divergent plate boundaries.6. This kind of fault occurs at convergent plate boundaries.7. Rocks above the fault surface are forced up and over the

rocks below the fault surface.8. Rocks above the fault surface move downward in relation

to rocks-below the fault surface.9. Rocks on either side of the fault boundary move past each

other without much upward or downward movement.10. Many of these faults occurred when the Sierra Nevadas

were formed.11. The Himalaya Mountains contain many of these faults.12. The San Andreas fault is an example of this kind of fault.IS. Rocks become twisted and strained when they snag

each other,

--------~--.-----

REINFORCEMENTEarthquakes and Plate Tectonicsm-ite tJu tmn that IMIchts each description btluw on th« spaw pnmidet.i. On€ lett6r has bmt given fur eachanswer.

1. 0_2. @J_.__!.0 _4._,_'_~_· _

5.@]_~ . _~----,---~- ------7~ __ ' OJ_ _ _8. 09. @] __

!0'110. ~_,_

n, llJ _1. 'This is the breaking of rocks that causes vibrations in Earth.t. Mosl earthquakes occur at the boundaries of these.3. These forces push on rocks from different, but not opposite, directions.4. Tension pulls rods apart and creates this.5. At these places, rocks are pushed from opposite directions.6. At these places, plates and the rocks that compose them are moving apart.7. A bending and stretching rock will break when it reaches this point.S. Rocks on either side of this move past each other without much upward or downward

movement.

9. One of the most famous examples of this boundary is the San Andreas fault in California.16. Here rocks above tlIia surface are forced up and over rocks below this surface.11. This force creates a normal fault.

Write t1u due leUm that wert given in the answe7l'.

lWfTange t~ ler.m tofrmn a word for INforc« the: creases reoers« faults.

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NAME DATE CLASS _

CHAPTER REVIEW Chapter 1-;

EarthquakesPart A. Vocabulary ReviewAfter each statement is a term that has been scrambled. Complete each statement l7y unscrambling the term andwriting it on the line provided.

1. Stress in Earth's crust leads to movement and changes in Earth's lithosphere that result in

__________________________ .eequraskhta

2. The force of tension at a divergent plate boundary causes a _manIor lauft

3. waves cause particles in rocks to move at right angles to thedirection of the waves. sandcorey

4. The of an earthqqake is the point on Earth's surface abovethe focus. rentpiece

5. The measure of energy released by an earthquake is the'earthquake's _gaindumet

6. A scientist who studies earthquakes is a ~_ . moistgilesos

7. At a fault, the rocks above the fault surface are forced up andover the rocks below the fault surface. servere

8. The ofan earthquake is the point in the Earth's interiorwhere energy is released. scouf

9. By studying seismic wave information, a scientist discovered the boundary between Earth's

crust and its upper man tie, which is called the Moho _dustcointinyi

10. A _:-- ---' is a seismic sea wave that can cause great devastation.natsium

11. One reason the loss of life was not great in the 1989 San Francisco Bay area earthquake was

that many structures were . micesis fesa

12. Most destruction in a earthquake is caused by waves. farceus

13. An instrument called a is used to record seismic waves fromearthquakes. gameshipors

'"14. At transform fault boundaries, faults are found. kirest-plis

15. waves cause particles in rocks to move back and forth in thesame direction as the waves. manyip

16. By measuring at three seismograph stations, scientists canlocate an earthquake's epicenter. ciInesis savew

Copyri;f1t GI.;tcoe Division of Macmillan/McGraw-HiliU5en of !rfenill EQrl#I Sd__ haw the publisher 5 permission 10 reprocIuce this page. 31