1. Earthquakes and other underground explosions
1.4 Seismic Waves
Earthquakes and other underground explosions

2. Wednesday 4/27/2016 Activator:
HW: 1.4 Seismic Waves Worksheet
Activator:
The diagram below shows an incident light ray striking a clear glass object. Draw and label the ray that will result, the angles that occur, and the normal line.

3. Daily Objectives Identify the types of Seismic Waves
Explain how a seismograph works.

4. Seismic Waves
Seismic waves: The waves produced by earthquakes and other explosions that travel through the earth.

5. Body Waves - Travel THROUGH the Earth Primary Waves Longitudinal
P Waves
S Waves
Primary Waves
Longitudinal
Arrive First – Travel the fastest
Go through rock and the earth’s core
Secondary Waves
Transverse
Cannot Travel through liquids
Do not travel through earth’s core

6. Surface Waves
Combination of P and S waves (Longitudinal and Transverse)
Travel the slowest
Cause the most damage because they combine side to side (longitudinal compressions) and up and down (transverse crests and troughs)
Tsunamis are huge ocean surface waves..
2 Types based on motion

8. Seismograph
Device used to measure the ground movements caused by seismic waves.
The frame is attached to the ground, so it moves as the ground does, the pen attached then makes a wiggly line. (Some newer ones are electronic)
Because P-Waves travel through earth faster than S-Waves, they are measured at the Seismograph first.
The difference in how long it takes for the P and S waves to arrive tells scientists how far away the earthquake was.
By using Seismographs located in different places, they can determine where the earthquake occurred.

9. Review of Daily Objectives
What are the 2 types of Body waves?
How are they different?
What is a surface wave?
How does a seismograph measure earthquakes?