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Earthquakes!

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Earthquakes! **Adapted from www.middleschoolscience.com What is an earthquake? Used to describe both sudden slip on a fault, and the resulting ground shaking and ... – PowerPoint PPT presentation

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Title: Earthquakes!

1
Earthquakes!
• Adapted from www.middleschoolscience.com

2
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 magma activity,
• Caused by other sudden stress changes in the
earth.

3
Three Types of Faults
Strike-Slip
Thrust
Normal
4
What causes earthquakes?
• Tectonic plates move past each other causing
stress. Stress causes the rock to deform, break,
and/or move

5
Elastic Rebound deformed rock goes back to its
original shape
http//www.uwgb.edu/dutchs/EarthSC-102VisualsIndex
.HTM
6
Focus point inside the Earth where an
earthquake beginsEpicenter point on Earths
surface above focus
7
How Seismographs Work
Its a weighted pen writing on a rolling drum of
paper.
the pendulum remains fixed as the ground moves
beneath it
this mass, like the pen, has inertia and so
resists motion.
Normally everything would move, but.
8
Typical Seismogram
http//isu.indstate.edu/jspeer/EarthSky/EarthCh11
.ppt
9
Primary Waves (P Waves)
• PUSH-PULL PATTERN!
• A type of seismic wave that pushes pulls the
ground
• The FIRST wave to arrive from an
earthquaketravels the fastest!
• Travels Parallel to the direction the wave travels

http//daphne.meccahosting.com/a0000e89/insideear
th2.htm
10
Secondary Waves (S Waves)
• A type of seismic wave that moves the ground up
and down or side-to-side (perpendicular) to the
direction the wave travels
• Slower!
• More destructive
• to buildings

http//daphne.meccahosting.com/a0000e89/insideear
th2.htm
11
(No Transcript)
12
Comparing Seismic Waves
P S Wave song http//www.youtube.com/watch?v
w3NLexYxR7g
13
Surface Waves
• Move along the Earths surface
• ROLL OUT! Motion can be up and down, around
back forth
• Travel more slowly than S and P waves
• Last to arrive
• Most destructive to structures

14
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 difference between the arrivals of the P
waves and the S waves

15
Locating Earthquakes
Question Where could the EQ be?
1. Find the difference in the arrival times, or lag
time ( t ), of the P S waves.

3. Use the distance from the EQ as the radius (r)
for this circle.
r
?Difference in arrival times?
P-wave
S-wave
2. Find the distance to the EQ using the lag time
and this Time/Distance graph.
Time ( t)
Answer Anywhere along the blue line. (not much
help)
Distance (km)
16
Locating Earthquakes
Question Where could the EQ be, now?
Lets get someone else that has readings for
this EQ to help out (Same procedure)
?Difference in arrival time?
\?Arrival diff.?\
Answer Where the green and blue circles
cross. (Better, but still a 50-50 change of going
to the right place to find the EQ.)
17
Locating Earthquakes
So, no more guessing Question where is the
actual EQ ?
If you get 3 people working on this puzzle, now
you can triangulate.
?Difference in arrival time?
\?Arrival diff.?\
\?Arrival time diff. ?\
Answer Where all 3 circles intersect
18
How are Earthquakes Measured? Richter
Scale-measures energy
19
How are Earthquakes Measured? Mercalli
Scale-measures damage
Click Link for Interactive Demo
http//elearning.niu.edu/simulations/images/S_port
folio/Mercalli/Mercalli_Scale.swf
20
Earthquake Waves Earths Interior
See how seismic waves move through the Earths
layers here (Shadow zone) http//www.classzone.co
m/books/earth_science/terc/content/visualizations/
es1009/es1009page01.cfm
21
Seismic Waves in the Earth
http//www.uwgb.edu/dutchs/EarthSC-102VisualsIndex
.HTM
22
Tsunamis
http//www.uwgb.edu/dutchs/EarthSC-102VisualsIndex
.HTM
23
Formation of a tsunami
http//isu.indstate.edu/jspeer/EarthSky/EarthCh11
.ppt
24
Tsunami Warning System
http//isu.indstate.edu/jspeer/EarthSky/EarthCh11
.ppt