Chapter 4 Lesson 2
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Earthquakes and Seismic Waves Study Guide
1. Earthquake: The shaking that results from the movement of rock beneath Earth’s
surface.
2. Focus: The point beneath Earth’s surface where rock first breaks under stress and causes
an earthquake.
3. Epicenter: The point on Earth’s surface directly above an earthquakes focus is the
epicenter.
4. P wave ( Primary wave): A type of seismic wave that compresses and expands the
ground.
5. S wave (secondary wave): A type of seismic wave that vibrates from side to side or up
and down.
6. Surface Wave: A type of seismic wave that forms when P waves and S waves reach
Earth’s surface and produce the most severe ground movements.
7. Sesimograph: A seismograph is an instrument that records and measures an earthquake’s
seismic waves.
8. Modified Mercalli Scale: A scale that rates the amount of shaking from an earthquake –
rated by people’s observations, without the use of any instruments and uses Roman
Numerals.
9. Richter Scale: A scale that rates an earthquake’s magnitude based on the size of its
seismic waves.
10. Moment Magnitude Scale: A scale that rates an earthquake by estimating the total
amount of energy released by an earthquake and is used today by geologists.
11. Magnitude: The measurement of an earthquake’s strength based on seismic waves and
movement along faults.
12. Seismic Waves: Vibrations that travel through Earth carrying the energy released during
an earthquake are seismic waves.
13. What are the three main categories of seismic waves?
P waves (primary waves), S Waves (secondary waves), and Surface waves