2.  Earthquake Zones
• About 95 percent of the major earthquakes occur in a few narrow zones.

3. 8.2 Waves and Location seismograph seismogram
 Seismographs (seismometer) - instruments that record earthquake waves.
 Seismograms - traces of amplified, electronically recorded ground motion made by seismographs.
seismograph
seismogram

4. Seismograph/ Seismogram

5. P = Compressional (Pressure)
Types of Waves
Earthquake Waves
 Body Waves - identified as P or S waves
P = Compressional (Pressure)
 P-waves: primary waves
- Push-pull waves - push (compress) & pull (expand) in the direction that the waves travel
- LONGITUDINAL waves
- Fastest speed (velocity) of all quake waves
- Travel through solids, liquids & gases
km/sec

6. Types of Waves S = Secondary  S-waves: secondary waves 1 - 5 km/sec
- Shake particles at right angles
to the direction that they travel
- TRANSVERSE waves
- Travel along Earth’s outer layers
- travel only through solids!!!!!
- Cause more damage than
p-waves
1 - 5 km/sec

7. Love Waves and Rayleigh waves
Types of Waves
Love Waves and Rayleigh waves
 Surface waves
- only move across Earth’s surface
- Combination of Earth moving up &
down and back & forth
- Most destruction due to longer
wavelengths

8. S Wave P Wave Surface Wave Fault line the difference in time
between the S and P wave
(S-P)
tells you how far away
the earthquake is

9. Where is it??? Locating an Earthquake
 Earthquake Distance (Triangulation)
• Epicenter - located using difference in arrival times between P and S wave recordings.
 Earthquake Direction
• Travel-time graphs from 3 or more seismographs used to find exact location of the epicenter.
 Earthquake Zones
• About 95% of major earthquakes occur in a few narrow zones

10. Locating an Earthquake
Explaining Earthquakes