1. How often do earthquakes occur?
Once a year
Once a month
Once a week
Once a day

2. Earthquakes Seismology  Seismologist  Fault  Deformation 
Elastic rebound 
study of earthquakes
scientist who studies earthquakes and seismic waves
a break in the crust along which plates shift and slip past each other
rocks changing shape due to stress from tectonic motion
stress builds up to the point where the rock breaks and snaps back

3. Epicenter – the point on the Earth’s surface directly above an Earthquake’s starting point
Focus – the point inside the Earth where the earthquake begins

4. Seismic Waves  vibrations that are generated by the earthquake and travel through the Earth
P-waves
S-waves
L-waves
Full name
Where they travel
Relative speed
Type of motion
pressure waves
(primary)
shear waves
(secondary)
Surface
through the entire earth
only through solid
on the earth’s surface
slowest, but most damaging
fastest
slower
up & down, and side to side (circle)
back and forth
up and down

5. Surface wave

6. Seismic Wave Motion with Surface Effects
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7. Seismic Wave Motion
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8. Measuring Seismic Waves
Seismograph – Instrument that record waves
Seismogram – Printout of waves created by seismograph

9. Seismographs
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13. Predicting Earthquakes (SCEC)
Italian Seismologists:

14. Earthquake Strength and Intensity
What is the measure of the strength of an earthquake called?
Magnitude
measures the strength of the ground motion
Richter scale 
Based on a factor of _____ for each level.
A magnitude 3 is ____ times as strong as a magnitude 2.
A magnitude 4 is ____ times as strong as a magnitude 3.
A magnitude 4 is _____ times as strong as a magnitude 2. 10 10 10
100
Historic Earthquakes
Chile May 22 19:11:14 UTC Magnitude 9.5
The Largest Earthquake in the World

15. Mercalli Scale
Measures Intensity – how much it is felt by people and how much damage it causes
Not as scientific because
not based on seisomogram recordings but on peoples’ observations
areas closer to epicenter will have higher intensity
damage depends on quality of construction

16. S Waves Arrive
P Waves Arrive

17. Identify the Richter Scale Magnitude of the earthquake
Las Vegas Seismic Station
What is the S-P lag time?
What is the distance to the earthquake epicenter?
What is the S-wave amplitude?
What is the magnitude using the nonogram?

18. AN earthquake with a magnitude of 5
AN earthquake with a magnitude of 5.0 on the Richter Scale will produce 10 times more ground motion as an earthquake with a magnitude of 4.0. How much more ground motion would an earthquake with a magnitude of 7.0 produce compared to an earthquake with a magnitude of 4.0?
Answer – 1,000 times more!!