seismology The study of seismic waves including earthquakes and the earth’s interior.
surface waves Surface waves are seismic waves that travel along the ground surface. The
two types are Love waves and Rayleigh waves. Surface waves do the most damage after
an earthquake.
trough The lowest point of a wave.
tsunami A deadly set of waves that are ordinarily caused by an undersea earthquakes or
another shock in which large amounts of seawater are displaced. Tsunamis rise high
on a beach and can travel far inland, causing death and destruction as they go.
wavelength The distance from crest to crest or trough to trough between two waves.
Points to Consider
- The last time there was a large earthquake on the Hayward Fault in the San Francisco
Bay area of California was in 1868. Use elastic rebound theory to describe what may
be happening along the Hayward Fault today and what will likely happen in the future. - Why is California so prone to earthquakes?
- How could coastal California be damaged by a tsunami? Where would the earthquake
occur? How could such a tsunami be predicted?
7.3 Measuring and Predicting Earthquakes
Lesson Objectives
- List the different types of seismic waves, their different properties and describe how
seismologists can use them to learn about earthquakes and the Earth’s interior. - Describe how to find an earthquake epicenter.
- Describe the different earthquake magnitude scales and what the numbers for moment
magnitude mean. - Describe how earthquakes are predicted and why the field of earthquake prediction has
had little success.
Introduction
Seismograms tell seismologists how strong an earthquake is and how far away it is. At
least three seismograms must be used to calculate where the epicenter is located. Over the