1. Earthquakes
Waves and Faults

2. Causes of Earthquakes
Plates in earth’s crust are always moving due to forces inside the Earth.
Forces cause sections of the crust to move.
This puts stress on the rocks.

3. Causes Cont. Rocks bend, compress and stretch to relieve that stress
If the force is great enough, rock breaks which make faults
Rock breaking or faulting produces vibrations called Earthquakes

4. 3 Types of Forces
Compression – Squeezes or compresses. Think two plates colliding
Tension – Stress causes stretching. Think two plates moving up and down.
Shear – causes slippage, rocks move past each other, side to side.

5. 3 Types of Faults Normal – caused by tension force
Reverse Fault – caused by compressional force
Strike-Slip Fault – caused by a shear (side to side) force

6. Seismic Waves Caused by fault movement
Vibrations from released energy produces waves
Produces
primary (p-waves), secondary (s-waves), and surface (l-waves)

7. Focus Point in the interior where waves originate
Can occur up to 700 km (434 miles) deep in the Earth.
Waves travel out in all directions from the focus.

8. Epicenter Point on Surface directly above focus
P and S waves generated from focus and generally travel through the interior of the Earth
When waves from focus reach the Epicenter they cause Surface waves
Surface waves travel out from the epicenter like ripples on a pond

9. Seismograph
Detects seismic waves, can detect earthquakes from the other side of the world.

10. Measurement
Richter Magnitude – measures the energy released by the earthquake. Base 10 scale
Mercalli Scale – measures the amount of damage produced by the earthquake

11. Primary Waves Type – Compressional, longitudinal
Speed – Fastest, 1st to register on seismograph
Motion – Back and forth rocking, least destructive
Movement Through Earth – Travels through any material: Solid rock, magma, water, or air

12. Secondary Waves Type – Shear or transverse
Speed – Slower, second to arrive
Motion – Side to Side
Movement Through the Earth – Only through solids.
Liquids and gases can not be sheared apart

13. Surface Waves Type – Like waves in Water
Speed – Slowest, last to arrive
Motion – Up/down rolling, like ripples. Cause the most damage
Movement Through Earth – Through solids and liquids