 By the end of this unit, you should be able to:  Discuss stress and strain and their roles in earthquakes  Identify and describe the 3 types of faults  Know the differences between elastic and plastic deformations  Know the 3 types of waves and how they are different from each other  Vocabulary from Chapter 11 in your book

 The shaking or trembling caused by the sudden release of energy  Usually associated with faulting or breaking of rocks

 Stress occurs when there is a force on the rocks.  Strain is the response to stress  1. Compression-squeeze together  2. Tension-pull apart  3. Shear- Slide Past

 Elastic deformation- low stress, material bends and stretches (pulling of rubber band- goes back into shape  Plastic deformation- stress builds past elastic point, causes permanent deformation  Failure - occurs when there is a rupture (Break)

 Crack in the earth where plates moves  Reverse Fault  Land being PUSHED together  Seen at convergent boundaries

 Land PULLING apart  Caused by tension  Divergent boundary

 Also known as a transform fault  Land block SLIDING PAST each other (Caused by horizontal sheering)  Example  San Andreas Fault in California

 Energy that is released by an earthquake  Energy travels in the form of waves  Three types:  P-waves (Primary)  S-waves (Secondary)  Surface Waves

 P or primary waves  fastest waves  travel through solids, liquids, or gases  compression wave, material movement is in the same direction as wave movement

 S or secondary waves  slower than P waves  travel through solids only  shear waves - move material perpendicular to wave movement

 Surface Waves  Travel just below or along the ground’s surface  Slower than body waves; rolling and side- to-side movement  Especially damaging to buildings

 Focus  The point within Earth where faulting begins is the focus---below the surface  Epicenter  The point directly above the focus on the surface

 Earth’s internal structure  Waves change speed and direction depending on the material they go through  S Waves do not go through the outer core  When the waves change scientists can gain information about the consistency and density of our earth’s layers  Shadow zone is created where no P or S waves travel

 Magnitude  Richter scale measures total amount of energy released by an earthquake; independent of intensity  Intensity  Modified Mercalli Scale  subjective measure of the kind of damage done and people’s reactions to it

 ~ 80% of all earthquakes occur in the Ring-of-Fire  most of these result from convergent margin activity  more than 150,000 quakes strong enough to be felt are recorded each year

Damage in Oakland, CA, 1989 Building collapse Fire Tsunami Ground failure