Transcript Features of Earthquakes

Features of Earthquakes
Chapter 11, Section 2
Prince William Sound,
Alaska
March 28, 1964
Magnitude 9.2
Denali Fault
Earthquake
M7.9
November 3, 2002
The survival of the Trans-Alaska Oil
Pipeline in the 2002 Denali Fault
earthquake demonstrates the value of
combining careful geologic studies of
earthquake hazards and creative
engineering in designing and
protecting such important structures
and lifelines.
What are Earthquakes?
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As rocks slide past each other along a fault,
rough areas can cause the rock to become
stuck.
Energy builds up in this “stuck” part of the
rock.
When enough energy builds up, the rock
reaches the elastic limit and moves a large
distance in a short amount of time.
When this movement occurs, energy is
released in the form of seismic waves.
Seismic Waves
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3 main types:
– Primary waves
– Secondary waves
– Surface waves
Seismic Waves
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Primary Waves (p-waves)
– Cause particles in rocks to compress and
then stretch apart (in the same direction
the wave travels).
– Fastest type of wave.
Seismic Waves
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Secondary Waves (s-waves)
– Cause particles in rocks to move back and
forth (at right angles to the direction the
wave travels).
Seismic Waves
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Surface Waves
– 2 types.
– Cause rock particles to
move in backward
rolling motion and a
side to side swaying
motion.
– Only travel on the
surface of the earth.
– Slowest type of wave.
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