Earthquake Notes

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Earthquake Notes
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What is an earthquake?

• Earthquake the shaking of the earths crust
  (remember waves transmit energy!).
• FrequencyOne happens somewhere on earth every
  30 seconds!

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What Causes Earthquakes?

• Caused when stress (the force per unit area) is
  greater than the strength of the rocks. Strain
  is when rocks deform due to stress.
• Causes of stress
• Shifting of tectonic plates
• Volcanic eruption
• Collapsing cavern
• Meteor impact
• Final Exams

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Epicenter and Focus

• Epicenter is the point on the surface of the
  earth directly above the focus of an earthquake.
• Focus is the place where a fault plane first
  ruptures during an earthquake

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Earthquake Calculations

• Seismograph is the machine used to measure the
  ground shaking during an earthquake
• Seismogram is the actual paper recording that
  shows the degree of ground shaking.

http//www.wwnorton.com/nrl/geology/earth/animatio
n_list.htm
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Remember Types of Waves?

• Primary Waves (P-Waves)
• cause particles in rocks to move back and forth
  in the same direction that the wave is traveling
• http//www.uh.edu/jbutler/physical/pwave.mov

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More Earthquake Waves!

• 2. Secondary Waves (S-Waves)
• Move through Earth by causing particles in rocks
  to move at right angles to the direction of wave
  travel
• http//www.uh.edu/jbutler/physical/swave.mov

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Yes, More Earthquake Waves!

• 3. Surface Waves
• Cause the most destruction
• Move rock particles in a backward rolling
  motion and a side-to-side, swaying motion
• http//www.uh.edu/jbutler/physical/rayleighWave.
  mov

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How Waves Indicate Composition
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Earth Does the Wave
Wave Fronts
Waves
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Savage Earth Unleashed!

• http//www.pbs.org/wnet/savageearth/animations/ear
  thquakes/main.html
• http//www.discoverourearth.org/student/earthquake
  s/index.html

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S-P Wave Lag Time

• S-P Lag Time is the time between the arrivals of
  P and S waves on a seismogram.
• Seismographs farther from the epicenter have
  longer S-P lag times.

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Travel Time Curve

• If you know the S-P lag time, you can use a
  time-travel curve to figure out the stations
  distance from the epicenter.

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Time Travel Curve
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Triangulation

• If you know
• The distance of three stations from the epicenter
• Then you can
• Determine the location of the epicenter using
  triangulation

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Type To Find an Epicenter!

• Work in groups of TWO.

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DES Today! Wednesday October 25th

• 10 minutes to finish lab if needed.
• Damage Scales and Faults (Targets 8 9)
• Pre-Lab the Friction Lab
• Tonights Homework
• Look up/define 4 more vocabulary words.
• Assess your understanding of targets 2- 6, 8-9

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Amplitude

• Amplitude is the height of a wave
• Amplitude indicates the amount of energy the
  wave transmits

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Richter Magnitude

• If you know
• the stations distance from the epicenter
• AND
• The amplitude of the wave
• Then you can
• determine magnitude using a Nomogram tool.

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What is a nomogram?
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Earthquake Severity

• Richter Earthquake Magnitudes Effects
• Less than 3.5 Generally not felt, but recorded.
• 3.5-5.4 Often felt, but rarely causes damage.
• Under 6.0 At most slight damage to well-designed
  buildings. Can cause major damage to poorly
  constructed buildings over small regions.
• 6.1-6.9 Can be destructive in areas up to about
  100 kilometers across where people live.
• 7.0-7.9 Major earthquake. Can cause serious
  damage over larger areas.
• 8 or greater Great earthquake. Can cause serious
  damage in areas several hundred kilometers
  across.

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Richter Scale, cont.

• Richter Scale starts at 1 (very small earthquake)
  and has no maximum value
• Largest earthquake recorded9.5 Chile, 1960

Effects of a 7.8 earthquake in 1906.
Although each earthquake has a unique Magnitude,
its effects will vary greatly according to
distance, ground conditions, construction
standards, and other factors. Seismologists use a
different Mercalli Intensity Scale to express the
variable effects of an earthquake.
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Earthquakes in Illinois
Info http//www.isgs.uiuc.edu/earthquakes/appgeop
hys_eq_home.htm Archive of Seismograms http//w
ww.isgs.uiuc.edu/earthquakes/appgeophys_eq_dp_arch
ive2004.htm
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Every Place Has Its Faults!

• A fault is a fracture in the Earth's crust along
  which two blocks of the crust have slipped with
  respect to each other.
• Faults are divided into three main groups,
  depending on how they move
• Normal faults
• Thrust (reverse) faults
• Strike-slip (lateral) faults
• http//www.iris.edu/gifs/animations/faults.htm

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Key Terms Know em, Love em
Hanging Wall- Always above the fault
plane Hangs on the footwall Foot Wall- Always
below the fault plane Shaped like a foot
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Stress, Stress, and More Stress!
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Normal Faults

• Occur in response to pulling or tension the
  overlying block moves down the dip of the fault
  plane.
• Most faulting along divergent boundaries
  (spreading zones) is normal.

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Hanging wall moves DOWN the footwall
Forces pulling apart rock (tension) create normal
faults
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Normal Faults
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Reverse Faults

• Occur in response to squeezing or compression
  the overlying block moves up the dip of the
  fault plane.
• Most faulting along subduction zones (convergent
  boundary) is thrust faults.

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Forces pushing rock together (compression) create
reverse faults
Hanging wall moves UP the footwall
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Reverse Fault
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Reverse Fault
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Strike-slip (lateral) faults

• Occur in response to either type of stress the
  blocks move horizontally past one another.
• Most faulting along transform faultsis
  strike-slip.

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Sideways motion (shearing) creates strike-slip
faults
Example San Andreas Fault
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• Strike-slip (shear)
• -fractures caused by horizontal shear

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Strike-Slip Fault
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Strike-Slip Fault
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Strike Slip Fault
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DES Today! Thursday October 26th

• Change of Plans!
• Target 12
• Tonights Homework
• Look up/define 4 more vocabulary words.
• Finish write-up of friction lab

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Latitude vs. Longitude

• Latitude-
• distance in degrees north or south of the Equator
  (0)
• Horizontal lines on a map

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Latitude vs. Longitude

• Longitude-
• distance in degrees east or west of the Prime
  Meridian (0)
• Vertical lines on a map

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Measuring Latitude and Longitude

• Each Degree is broken down into minutes
• (60 minutes in one degree)
• A minute is shown with a sign. (example 8806)

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To Open from School

• Open PowerPoint
• Click on Open
• In the Look In field, Select Global on
  Nccluster
• Open the folder labeled Pollard-DES
• Open the PowerPoint labeled Virtual Earthquake
  Measurement
• View the PowerPoint and then click on the address
  on the first slide.

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Virtual Earthquake Measurements

• http//vcourseware4.calstatela.edu/eec/
• Earthquake/
• Press Epicenter and Magnitude button
• Next, press Start Activity
• Wait for Pop-up, and Select Run on the following
  screen
• Class code 692784

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DES Today! Friday October 27th

• Target 12 Explain the roll of friction in
  earthquakes.
• Class Meeting
• Friction Lab (Write-Up Due Tuesday)
• Tonights Homework
• Look up/define 4 more vocabulary words.
• Assess your understanding of Target 12