Transcript What are Earthquakes

Do NOW!
Homework:
Study for EQ’s test (Tue. 1/12)
Work on project (Due Wed. 1/13)
Answer the following question on your Do NOW sheet!
Q: Where do most earthquakes take place?
A: Near tectonic plate boundaries
Take out classwork from yesterday and
turn it into the basket of your class
period!
Earthquakes
What are Earthquakes?
Earthquakes:
the sudden
movement of
Earth’s Crust!
Where Do Earthquakes Occur?
• Mostly occur near tectonic plate
• A break in the Earth’s crust where
movement occurs is called a fault.
The Three Types of Faults
Plate Motion
Transform
Boundary
(shearing)
Convergent
Boundary
(compression)
Divergent
Boundary
(tension)
Fault Name
Strike Slip Fault
Reverse Fault
Normal Fault
Fault Movement
Let’s make a model!
•
Half sheet of paper = Earth crust
On the Earth’s crust, divide into 3 sections
•
Simply color code each section with a different color
(to represent 3 layers of rock)
•
Fault it (break the Earth’s crust) 
•
Label the hanging wall and foot wall
F
H
What Causes Earthquakes?
• Deformation of the plates! Rocks that are
under stress can eventually break = EQ!
• Elastic Rebound = when rocks suddenly
break and spring back to their original
shape.
Check out the DEMO:
http://projects.crustal.ucsb.edu/understanding/elastic/rebound.html
How Do Earthquake Waves Travel?
There are 3 types of seismic waves:
1. Primary Waves: P-Waves
2. Secondary Waves: S-Waves
3. Surface Waves
Click Here for animation!
Primary Waves (P-Waves)
•
•
•
•
Move the fastest
Move in a straight line
Compress and expand like an accordion
Move through solids, liquids, and gases
P-Wave
Secondary Waves (S-Waves)
• 2nd fastest
• Vibrate side to side and up and
down
• Can only move through solids
S-Wave
Surface Waves
• Result of P-waves and S-waves when
they reach the surface
• Only travel in the crust!
• Slowest seismic waves
• Make the ground roll like ocean
waves
• Responsible for surface damage and
falling buildings.
Surface Waves
Notice the top is moving more than the bottom!
Surface Wave Diagram
How are earthquakes measured?
• Seismograph: records ground movements
of earthquakes
• The pendulum sits still while the ground
moves.
http://www.wwnorton.com/college/geo/egeo/flash/8_3.swf
What is the seismograph measuring?
• Epicenter: Center of earthquake ABOVE
GROUND
• Focus: Point where rocks break
UNDERGROUND
Earthquake Location
Earthquake Effects - Ground Shaking
Loma Prieta, CA 1989
KGO-TV News ABC-7
Earthquake Effects - Ground Shaking
Kobe, Japan 1995
Earthquake Effects - Ground Shaking
Kobe, Japan 1995
Earthquake Effects - Surface Faulting
Landers, CA 1992
Earthquake Effects - Landslides
Source: National Geophysical Data Center
Turnagain Heights, Alaska,1964 (upper left inset);
Santa Cruz Mtns, California , 1989