Seismology is the study of earthquakes and seismic waves that move through and around the earth.

What Are Seismic Waves?

Seismic waves are the waves of energy caused by the sudden breaking of rock within the earth or an explosion. They are the energy that travels through the earth and is recorded on seismographs.
Types of Seismic Waves

There are several different kinds of seismic waves, and they all move in different ways. The two main types of waves are body waves and surface waves.

Body waves can travel through the earth's inner layers, but surface waves can only move along the surface of the planet like ripples on water. Earthquakes radiate seismic energy as both body and surface waves.

1. Name and describe in detail the two types of body waves.

2. Name and describe in detail the two types of surface waves.

An earthquake is a sudden movement of rocks, caused by buildup of stress within the Earth, especially when adjacent plates move in different directions. When the stress exceeds the strength of rocks at a fault, an earthquake occurs, releasing energy partly in the form of earth vibrations (seismic waves) and partly by producing a sudden offset of the rock.

Areas tens-to-hundreds of kilometers from an earthquake are at risk from seismic waves, which can transmit energy through the earth for thousands of kilometers. Most earthquakes occur along the edge of the oceanic and continental plates.

10. Define a fault and describe three types of faults.

Geologists have used properties of P-waves and S-waves to predict the composition of Earth’s interior. They believe that Earth consists of three main zones: the crust, the mantle, and the core. They believe the core consists of a liquid outer core and a solid inner core.

P-waves and S-waves travel through various rock materials at different velocities.

S-waves cannot pass through molten (liquid) rock. If Earth’s composition were that of a uniform solid, the velocities of P-waves and S-waves would increase steadily with depth, because increasing pressure beneath the surface increases the elastic properties of the rock, which in turn increases wave velocities. However, the interior rock composition is not uniform; it changes with depth, so earthquake wave velocity does not increase smoothly, as shown in the graph below.

Use the graph and information from the website to answer the following questions:
3. How fast do P-waves move in the crust?

4. How fast do S-waves move in the crust?

5. What happens to S-waves approximately 2900 km below Earth’s surface? Why?

6. Using only data on P-waves, how could you determine the depth of the
   boundary between the mantle and the outer core?

7. How does P-wave speed indicate that the inner core is composed of solid rock?

8. S-waves can travel through solid rock, and the inner core is solid. Why then are
   no S-waves found in the inner core?

9. Which is likely to be a more distinct transition: from the mantle to the outer core
   or from the outer core to the inner core? Why?

The magnitude of an earthquake can be measured by two scales: the Richter Scale and the Mercalli Scale.

11. Compare and contrast both types of scales.