Download What are Earthquakes?

What are Earthquakes?
Where Do Earthquakes Occur?
•
•
Earthquakes occur near tectonic plate
edges.
A break in the Earth’s crust where plates
slide past each other 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
What Causes Earthquakes?
• Caused by deformation of the plates.
Rocks that are under stress and stretched
will eventually break, causing an
earthquake.
• Elastic Rebound = when rocks suddenly
break and spring back to their original
shape.
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 to P-waves
• 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
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
Earthquake Location