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San Francisco Earthquakes
• 1906 ~ 7.8
• 1989 – 6.9
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• Earthquake/Volcano plots
• Earthquake
Pg. 24
Pg. 25
• What are the top 3 states for earthquake
activity(3.5 or higher)?
• Out of the 50 states, where do you think
Nevada ranks?
1Alaska:
The number of earthquakes is under reported, even though Alaska already accounts for more than 50
percent of all US earthquakes! Events in the magnitude range of 3.5 to 4.0 in the Aleutian Islands are not recorded
on enough seismograph stations to be located.
2Hawaii: The earthquake count was obtained from the USGS Hawaiian Volcano Observatory (HVO). Hawaii and
Nevada are essentially tied in the rates of earthquakes of magnitude 5.0 and greater.
Oklahoma is now #1
Earthquakes Pg. 25
• Earthquake-sudden movement of the ground
caused by the release of energy when the
rocks move along a fault.
• Fault-a break in rock where movement occurs.
Where do most earthquakes occur?
• Most earthquakes occur at plate boundaries or
faults, where there is a lot of stress.
• Friction prevents the plates from moving until the
stress is too great and the rocks suddenly grind past
each other =trembling and vibrations that are felt.
• Elastic Rebound – the
sudden return of the
deformed rock to its
undeformed shape.
(Yes, draw this!)
Anatomy of an earthquake
• Focus-where the first movement occurs in the
earth’s crust.
• Epicenter-point on the earth’s surface directly
above the focus.
This is a map of all the known faults in the Las Vegas Valley. The brown lines are East-dipping
normal faults. The yellow line is a West-dipping normal fault, and the green lines are inactive
faults.