Earthquakes and Seismic waves

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Earthquakes and Seismic waves
Shake it Up!
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Earthquakes

• __________________________________________________
  _______

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Elastic Rebound Theory

• As plates move blocks in opposite directions
  __________________________
• Rocks will ________________________
• The strain will continue until the
  ________________________ there is slip along
  the fault plane
• The ________ released is an earthquake

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The strain will continue until the friction lock
is broken there is_______________
___________________________
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Seismic Waves

• Can be _____________________ or any other large
  energy release
• The energy is released in a series of
  ___________________

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Two Main Varieties

• Body waves
• __________________________________________________
  ______________
• Surface waves
• __________________________________________________
  _______________

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Body waves

• P-waves
• __________________ fastest 6-13 km/sec( their
  speed will depend on the material through which
  they are traveling)
• ___________________________
• Travel through _________________________
• The____________________________________
  ________________________________________

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• Particles move ______________________

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• S-waves
• ________________________ they travel about ½ as
  fast as P- waves
• ________________________________
• Can not travel through ___________

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• Particles move _______________to wave motion

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Surface waves

• Travel through the Earths crust
• ______________________
• ______________________

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• Rayleigh waves
• A little slower than the S-wave 2-4km/sec
• Travel in a __________________________

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• Love Waves
• Travel more slowly than an S-wave 2-4km/sec
• _______________________________
• _________________ (snake-like) motion is at a 90
  angle (horizontally) to the wave direction

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Seismic Bonus

• Seismic waves also tell us about the
  ______________________________
• Because P S waves speed up through material
  that is more dense, we can calculate
  the_________________________ _____________________
  ____________

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The Moho

• __________________________________________________
  ________________________
• Discovered by Andrija Mohorovicic in 1909.
• He observed the ___________ in speed of seismic
  waves when they passed below the crust.

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Shadow Zones

• More can be discovered about the layers of the
  Earth through shadow zones
• __________________________________________________
  _________________

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• Because P S waves are ____________
  ______________________there are places on the
  Earth where a certain EQ will not be felt

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• S-waves will not travel through the
  __________________________.
• S-wave shadow zone is 103º - 180º
• P-waves will travel through it but will
  __________________________
• P-wave shadow zone is from 103º - 142º

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• Because of these wave characteristics, the
  ______________________ in all the layers can be
  inferred.

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Earthquakes

• Earthquakes are more common than you think!
• __________________________________________________
  ___________

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Earthquake Vocabulary!

• Slip
• __________________________________________________
  _____
• Fault Plane
• __________________________________________________
  ______

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• Focus
• __________________________________________________
  ______
• Epicenter
• __________________________________________________
  ______

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Focus vs. Epicenter
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Focus Depth

• Shallow Focus
• _____________________________
• Within ________________ of the surface
• Make up __________ of the continental EQ

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• Intermediate focus
• Occur within _______________ of the surface
• Deep focus
• Occur between _____________________
• Mostly happen in _______________________

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Seismographs

• Seismographs will measure both the
  ___________________________ of the waves

Seismographs have pendulums that are suspended in
a tube. The electrical force required to keep the
pendulum centered in the tube is recorded and
measured.
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• The seismograph will transfer data that is
  recorded as a _______________.

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• Because S P waves travel at different speeds,
  they will arrive at the seismograph at different
  times.
• The difference in arrival times is called
  ________________

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Lag time to Distance

• Because we know the rough speeds of both P and S
  waves in the earth, we can use the lag time
  recorded by a seismograph to _____________________
  ______________
• How do we do this?
• Lets do a few calculations where we assume a 100
  km distance between seismograph and epicenter...

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• Typical P wave speed 6.1 km/s, Typical S wave
  speed 4.1 km/s
• Remember Distance / Speed Time
• So if distance is 100 km
• P waves get to seismograph _______________
• S waves get to seismograph _______________
• Therefore if you are 100 km away, you should
  expect a lag time of _______________.

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• Now that we know a distance and lag time we can
  set up a _____ to determine any other pair.
• Distance to Epicenter in km 100 km
• Measured Lag Time in seconds 8 sec
• This ratio can be used with any measured lag time
  to _________________________ between epicenter
  and seismograph

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Triangulation

• EQs (as well as other things). can be found using
  ________________
• Using the distance from______________
  _______________________, the epicenter can be
  pinpointed.

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• At this EQ station, the S-wave lagged
  _____________ behind the P-wave
• The amplitude of the S-wave is 23mm

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• A chart can be
• used to find
• the magnitude
• of the EQ

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• By using data like this from 3 locations, the
  __________________________ can be calculated

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Richter Scale

• The Richter scale measures the _____________ of
  an Earthquake
• Magnitude relates to__________________
  ________________________
• Based on _____________________________
• Is a _________________________________

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• The Richter Scale is numeric and goes up to 10
• It is____________________________________
  ________________________________________

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• ________________________ as the whole number
  increases by 1, the amplitude of the wave is
  increasing by 10.
• ______________________
• Each whole number jump represents about
  ______________________ as the previous number

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• An EQ with a magnitude of 6.3 is _____
  __________than an EQ with a magnitude of 4.3

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Modified Mercalli Intensity Scale

• Mercalli ____________________________
• Includes ____________________________
• Not a mathematical scale,_____________
• ___________________

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• I. Not felt except by a very few under especially
  favorable conditions.
• II. Felt only by a few persons at rest,
  especially on upper floors of buildings.
  Delicately suspended objects may swing.
• _ _ _ _
• XI. Few, if any (masonry) structures remain
  standing. Bridges destroyed. Rails bent greatly.
• XII. Damage total. Lines of sight and level are
  distorted. Objects thrown into the air.

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Mercalli Scale

• Takes into account
• Size of quake
• Bigger Richter __________________________
• Distance to quake
• ________________________ more damage
• _______________________
• Military bunker vs. tree fort made by 6 year olds
• _______________________
• Asleep when quake hit?

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Rank the EQ

• For many locations, there are websites that the
  general public can go to and input your Mercalli
  ranking.
• New England
• California

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Global Distribution of EQs

• Pacific Ring of Fire
• ________________________
• _______________
• Stretches from Europe and Mediterranean through
  Asia and the Himalayas to Java and Sumatra.
• _______________________

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Earthquake Hazards!

• Both minor and severe EQs can pose hazards when
  and after they occur.

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Liquefaction

• Wet loose soil behaves____________________
  ______________________________
• For about 5 - 60 seconds (depending on quake it
  will have the _______________________.
• Buildings will ________________ during this time.
• Soil then becomes solid again and buildings are
  stuck in whatever position they were in.

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Liquefaction Niigata, Japan 64
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Tsunami

• Japanese word for _________________
• Not a typical surfing wave
• First the water goes out real far, real fast
• Then it all rushes back in. Looks like the tide
  is coming in extra fast.

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Landslides Avalanches

• If a slope is almost as steep as it can be, an
  earthquake can___________________
  __________________________.
• Can happen by horizontal forces
• Or, the toe of the slope can undergo
  liquefaction.

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Fires Floods

• ____________ caused from broken gas mains being
  ignited by power lines
• ________ are caused by broken water mains
• The arrival of emergency vehicles can be delayed
  by______________________ ______________________

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Preparedness

• __________________________________________________
  ______.
• Many injuries are caused by falling light
  fixtures.
• Water heater and utility lines (make flexible
  connections)
• ___________________________
• ___________________________
• Flashlight, sturdy shoes, water

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If it happens

• __________________________!
• Get inside a doorway if possible.
• Under a sturdy table is also good.
• If possible cover your head with a pillow.
• Against a wall is ok, IF nothing is hanging on
  the wall above your head.

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• After the shaking, look at the walls of your
  building. If they look_____________
  ___________________ evacuate the house until it
  can be inspected by a professional.

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Can it happen here?

• ______!
• But dont spend too much time worrying about it.
  Odds are low (_______________) that a large quake
  (gt Mag 6.0) will happen anytime soon.

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• Due to the_________
• _____________ and
• various mountain
• ranges, the effects
• from a large
• southern Earthquake
• could be more
• ______________ than
• that of a large
• California
• Earthquake!

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Famous Big Earthquakes

• _________________________________ - 1960
• 2000 killed by quake, 220 by tsunami
• 680 million
• _________________________________ 1964
• 125 killed
• 311 million in damage
• __________________________ Christmas 2004
• Over 280,000 killed by tsunami
• Damages still being tallied

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New Madrid, Missouri

• Winter 1811-1812
• ________________________ occurred in this winter
• At one point _________________________ as a
  result of the seismic waves
• Seismic waves traveled very far because of
  ______________________

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• The New Madrid Fault system is an
  _________________________________
• This fault system developed over
  __________________________

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1906 San Francisco

• Occurred on April 18th
• One of the ____________________ of all time
• Measured _______________________ and was even
  picked up by seismographs in Germany

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• ______________ people died
• ______________ people homeless
• ______________ buildings damaged

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• Provided important scientific information about
  how______________ __________________ they occur
  in
• This EQ lead Reid to formulate the
  ___________________________.

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1998 Loma Prieta, CA

• Measured ________ on the Richter scale
• There was a ___________ along the San Andreas
  Fault system.

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