Download - Earthquakes ppt for class
Earthquakes
Adapted from powerpoint by Liz LaRosa http://www.middleschoolscience.com 2009
What Is An Earthquake? Click here to find out
What is an earthquake?• Used to describe both sudden slip on a fault, and the resulting
ground shaking and radiated seismic energy caused by the slip• Caused by volcanic or plate activity,
The map above shows the distribution of earthquakes with magnitudes greater than 5.0 that occurred between 1965 and 1995.
http://eqseis.geosc.psu.edu
Three Types of Faults
Strike-Slip
Normal
Reverse
Animation of fault movement
Normal fault
Pulls on the crust stretching rock so that it becomes thinner (like pulling on bubble gum) = tensionOccurs when plates are moving apart
Results in hanging wall slipping downward
Hanging wall
Foot wall
animation
What type of fault?
Hanging wallFoot wall
http://www.bgs.ac.uk/eqr/GeoD_Structures.htm
normal
What causes earthquakes?
• Tectonic plates move past each other causing stress. Stress causes the rock to deform– What type of fault boundary is this?– What type of stress is shown?
transform
shearing
Strike – slip fault
Rocks on either side of fault slip past each other sideways with little up or down motion -
Animation of strike-slip motion
Occurs at a plate boundarytransform
shearingWhat type of stress is produced?
Fault rupture across road in western Kaynasli, right-lateral strike slip displacement was about 4.0 m (13 feet) at this location http://www.geerassociation.org/GEER_Post%20EQ
%20Reports/Duzce_1999/kaynasli1.htm
Reverse fault
Pushes on the crust squeezing rock until it folds or breaks (like a trash compactor) = Occurs when plates are moving together
Results in hanging wall slipping upward
Hanging wall
Foot wall
animation
compression
What type of fault?
Hanging wall
Foot wall
http://geologicalintroduction.baffl.co.uk
reverse
What type of fault?
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM
– 1. point inside the Earth where an earthquake begins
– 2. point on Earth’s surface above focus where earthquake is FELT most strongly
Epicenter
Focus
1
2
How Seismographs Work
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM
the pendulum remains fixed as the ground moves beneath it
A seismograph is an instrument used for recording the intensity and duration of an earthquake.
Earthquakes
• How are earthquakes measured?
Seismograph machine
Seismogram – seismic wave display record
Seismic Waves
Primary Waves (P Waves)
• A type of seismic wave that compresses and expands the ground
• The first wave to arrive at an earthquake
http://daphne.meccahosting.com/~a0000e89/insideearth2.htm
Secondary Waves (S Waves)
• A type of seismic wave that moves the ground up and down or side to side
http://daphne.meccahosting.com/~a0000e89/insideearth2.htm
Comparing Seismic Waves
Surface Waves
• Move along the Earth’s surface• Produces motion in the upper crust
– Motion can be up and down– Motion can be around– Motion can be back and forth
• Travel more slowly than S and P waves• More destructive
Animation of wave types
How do scientists calculate how far a location is from the epicenter of an earthquake?
• Scientists calculate the difference between arrival times of the P waves and S waves
• The further away an earthquake is, the greater the time between the arrival of the P waves and the S waves
Typical Seismogram
http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt
startstart finishfinish
How much time elapsed between the arrival of the P wave (start) and the arrival of the S wave (finish)?
Locating Earthquakes
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM
Locating Earthquakes
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM
Now you are going to be seismologists and locate an Earthquake
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM
Go to: http://tinyurl.com/11quake13
Click here to go to virtual earthquake site
National Geographic earthquake information
How are Earthquakes Measured? Richter Scale
A logarithmic scale used to express the total amount of energy released ___________ of an earthquake. Its values typically fall between 0 and 9, with each increase of 1 representing a _________ increase in energy.
magnitude
10-fold
How are Earthquakes Measured? Mercalli Intensity Scale
Click for Interactive Demo Go to http://tinyurl.com/13quake13
A scale of earthquake intensity based on ___________and ranging from I (detectable only with instruments) to XII (causing almost total destruction).
observed effects
Earthquake Waves & Earth’s Interior
Seismic wave animation
Seismic Waves in the Earth
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM
Click here for animation
Tsunamis
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM
Click here for explanation of a tsunami
Formation of a tsunami
http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt
PBS –tsunami animation
a large ocean wave usually caused by an underwater earthquake or a volcanic explosion.
Click here for Japan helicopter view of tsunami
With typical waves, water flows in circles, but with a tsunami, water flows straight. This is why tsunamis cause so much damage!
Tsunami Warning System
http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt
Review Questions
1. A large ocean wave usually caused by an underwater earthquake or a volcanic explosion.
tsunami
2. Used to describe both a sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip
earthquake
How are Earthquakes Measured?
3. Which one uses a logarithmic scale to express the total amount of energy released or magnitude of an earthquake.
Richter Scale
4. Which uses a scale of earthquake intensity based on observed effects and ranging from I (detectable only with instruments) to XII (causing almost total destruction).
Modified Mercalli Scale
What type of fault is shown by each picture?
1.2.
3.
NormalReverse
Transverse or strike-slip
Which type of wave travels through solids only?
S-wave
Which type of wave causes the most destruction?
Surface or Love waves
What type of fault?
AHanging wall has moved
http://geologicalintroduction.baffl.co.uk B
Source: indiana.edu
Reverse fault
upwardStrike –slip or transverse fault
– 1. point inside the Earth where an earthquake begins
– 2. point on Earth’s surface above focus where earthquake is FELT most strongly
Epicenter
Focus
1
2
People walk along a damaged road in the province of Bohol on Tuesday, October 15, 2013.
Do you think this was a major earthquake? Why or why not?
Yes, it was a major quake.It crumbled a number of buildings
Such as this church
7.1 magnitude earthquake hit the Philippines
Earthquakes
5. __________ machine
____________ seismic wave display record
Seismograph
P-wave
Surface
2.
3.
4.
1. S-wave
Seismogram