Download Earthquake Waves

The Where of Plate
Tectonics
Evidence for Plate Boundaries
• Divergent Boundaries
– Volcanoes
– Ocean Ridges
– Seafloor Spreading
– Rift Valley
• Convergent Boundaries
– Volcanoes
– Volcanic Mountain Arcs
– Volcanic Island Arcs
– Mountain Ranges
• Transform Fault Boundaries
– Earthquakes
What is an Earthquake?
What Is an Earthquake?
Earthquake - vibration of Earth produced
by rapid release of energy
Earthquake Waves
During an earthquake, energy is released in the
form of waves.
P Waves
S Waves
Surface Waves
Earthquake Waves
P waves
Are push-pull waves that push (compress) and pull
(expand) in the direction that the waves travel
Travel through solids, liquids, and gases
Have the greatest velocity of all earthquake waves
Earthquake Waves
S waves
Seismic waves that travel along Earth’s outer layer
Shake particles at right angles to the direction of
travel
Travel only through solids
Slower velocity than P waves
Earthquake Waves
Surface waves
Seismic waves traveling along Earth’s surface
Slowest of the seismic waves
Questions About Earthquake
Waves
1. An earthquake occurs 100 miles away. In
what order will the waves arrive at your
location?
2. Which waves do you think are most
dangerous? Why?
3. Suggest how earthquake waves have been
used to develop our model of the Earth’s
interior? Think about what the inside of
Earth looks like.
Locating Earthquakes
Earthquake Waves
Seismographs are instruments that record
earthquake waves.
Seismograms are traces of amplified, electronically
recorded ground motion made by seismographs.
Locating Earthquakes
 Earthquake Distance
• The epicenter is located using the difference in
the arrival times between P and S wave
recordings, which are related to distance.
 Earthquake Direction
• Travel-time graphs from three or more
seismographs can be used to find the exact
location of an earthquake epicenter.
 Earthquake Zones
• About 95 percent of the major earthquakes
occur in a few narrow zones.
Locating an Earthquake Lab
Delineating Plate Boundaries