1. Earthquakes

2. Earth’s Plates
Earth’s lithosphere is divided into plates (continental and oceanic) which float and move on the mantle.
Plate Tectonics Video Segment

3. Faults Surfaces along which rocks move, fracture, and are displaced.
Stress builds along faults, causing the rocks to bend and stretch. When they reach their “elastic limit”, they break = Earthquake
There are three types of faults:

4. 1. Strike-Slip Fault Plates move past each other (sideways)
Caused by shearing forces

5. 2. Normal Fault Rock moves below the fault surface.
Caused by the force of tension, which pulls the rock apart.

6. 3. Reverse Fault Rock moves above the fault line
Caused by compression forces in which rocks are pushed together.

7. Earthquakes
Occur as a result of motion along a fault when energy is released
Produce seismic waves – carry energy through the Earth

8. Focus – the point in the Earth where the energy is released
Seismic waves are produced and travel outward from the focus.
Epicenter – the point above the focus on the Earth’s surface.

9. Types of Seismic Waves P waves Primary waves
P waves
Primary waves
Move back and forth in the same direction as the wave is moving
Fastest moving waves

10. S waves Secondary waves
S waves
Secondary waves
Particles move at right angles to the motion of the waves (up and down)

11.
Surface waves
Particles move in an elliptical motion as well as a back-and-forth motion.
Slowest moving waves
Cause the most damage

12. Seismograph Seismic waves are measured with a seismograph
akes/seismo/