Objectives

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• Objectives
• 1. Compare the 3 types of seismic waves.
• 2. Discuss the method scientists use to
  pinpoint an Earthquake (EQ).
• 3. Discuss the method most commonly used to
  measure the magnitude of EQs.

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3 major Types of Seismic Waves

• P waves primary wave.
• ____________________
• 1st to be recorded
• Travels through _________ ________
• More rigid material. _____________

Move fastest
Liquids
Solids
Faster
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3 major Types of Seismic Waves

• S waves secondary waves.
• 2nd waves to be recorded
• Only travel trough __________________

Solids
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3 major Types of Seismic Waves

• L waves surface waves, also called ____________
  waves.
• Converted from P S waves when they reach they
  ____________________
• Slowest-moving waves
• __________________ to be recorded
• Cause surface to rise fall

Long
Reach the surface
Last
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Comparing Seismic Waves
Primary Waves (P) Secondary Waves (S) Long or Surface Waves (L)
Arrives _____ Moves faster through more __________ material Moves the ground together and apart along the direction of ___________. Arrive ______ About _______ Xs slower than the P- waves Moves faster through more rigid material Moves the ground at _______ angles to the direction in which the waves are traveling Arrives last ___________ of the 3 Travels over the earths surface Moves the ground like the ___________ waves Can cause great _____________ when traveling through loose earth
2nd
1st
slowest
1.7
rigid
ocean
right
waves
damage
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Recording EQs

• Seismograph _________________ ___________________
  __________.
• Determines the ____________and not the
  _________________ of the epicenter.

instrument used to detect and record seismic waves
distance
direction
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Locating an EQ
Distance-Determined by seismograph- scientists
analyze the ____________ between the arrival
times of the ____ and the _____ waves. Locating
the epicenter-At least 3 seismograph is needed to
locate the epicenter. The method is called
_____________.
difference
P
S
Triangulation
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Two recording N.S and E.W vibrations
One recording vertical vibrations
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Locating an EQ

• Scientists compare time diff. btwn P S waves.
• Plot on graph to get distance to ____________

Epicenter
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Triangulation
EX 3 seismographs at locations A, B, and C,
determined the distance of each point from the
epicenter. Point A (seismograph 1)is 500 km,
point B (seismograph 2) is 800 km and point C is
1200 km (seismograph 3) away from the epicenter.
Locate the epicenter.
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Locating an EQ

• Need ____ plots to locate epicenter
• Point where all 3 circles meet is location of
  __________________

3
Epicenter
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EQ Scales
Richter Scale Mercalli Scale
Measures the ___________ or the energy released by an earthquake. Scale of 1 to 10 Each level releases ______ times more energy than that of the lower level Largest registered, ______ in Chile 1960. Strong-______ or above Moderate ______ Minor-________ ____________-2.5 or less. Can not be felt by people Expresses the _________ or the amount of damage it causes. Shown by Roman numerals from _______________. I-II- Low intensity, ___________________ Up to ______- Higher intensity, well built structures destroyed. XII- ______________ ___________________
magnitude
intensity
31.7
I-XII
9.5
Little damage
X
7
6-7
2.5-6
total
destruction
Microquakes
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EARTHQUAKE DAMAGE

• Movement of the ____________ itself seldom causes
  many deaths or injuries.
• Most injuries result from the collapse of the
  buildings, ___________________ and falling
  objects.

ground
Flying glass
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Damages
Flood

Fire Landslide

• Most buildings are not designed to withstand the
  swaying motion caused by ______________________.
• Buildings may collapse, sway violently, or tip
  over to the neighboring structure.
• Tall buildings should be built on soil or rock
  that is firm. Loose soil and rock can vibrate
  like jelly.

earthquakes
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Tsunami (harbor wave)
_____________ and under water ______________ can
cause tsunamis. Tsunamis can cause massive death
and damages.
Faulting
landslides
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SSWWS
Seismic Sea Wave Warning System Seismic network
around the Pacific Ocean.Allows scientists to
estimate the arrival times of the
_________________ at different locations.
tsunamis