Earthquakes

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Earthquakes
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Aim What are Earthquakes and their
characteristics?
I. Earthquakes any vibrating, shaking, or rapid
motion of Earths crust.
A. Fault zone of weakness or a break in the
rock.
1. When the stress exceeds the ability of the
crust to resist breaking, the crust shifts and
energy is released suddenly.
B. Focus place underground where break occurs.
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C. Epicenter the location at the surface just
above the focus.
D. Seismic waves (shock waves) earthquake waves
1. Primary (P) waves the first waves to arrive.
Fastest wave that can travel through any
material. P-wave animation
Another P-wave animation
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2. Secondary (S) waves second wave to arrive.
Slower than P wave and cannot travel through
liquids. S-wave animation
Another S-wave animation
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P wave motion
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S wave motion
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E. Measuring Earthquakes
1. Seismometers detect vibrations of the ground.
2. Seismograph instrument that detects and
records seismic waves.
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3. Richter scale a scale from 1 10 that
measures the magnitude of an earthquake.
a. Each increase of one unit means a ten-fold
increase in shaking.
b. For example, an earthquake that measures a 5
on the Richter scale is 10 times greater than an
earthquake that measures a 4 on the Richter
scale. An earthquake that measures a 5 on the
Richter scale is 100 times greater than an
earthquake that measures a 3 on the Richter
scale. (5-32. 10 x 10 100)