 I. What Are Earthquakes?  A. Where Do Earthquakes Occur?  1. seismology  a. study of earthquakes  2. seismologist a. scientist that studies earthquakes  3. Faults  a. break in the earth’s crust  b. blocks of crust slide past each other  c. earthquakes occur along faults

 B. What Causes Earthquakes?  1. Deformation  a. rocks deform as result of stress  b. plastic deformation – deforms like clay – no earthquakes  c. elastic deformation – stretches, breaks and returns to original shape earthquakes  2. Elastic rebound  a. sudden return of elastically deformed rock to original position  b. more stress is applied than rock can withstand  c. energy is released  d. seismic waves can cause earthquakes

 C. Faults at Tectonic Plates  1. Earthquake Zones  a. near the surface or far below  b. most happen at tectonic plate boundaries  c. not all faults located at boundaries  d. earthquakes can happen along faults in the middle of plates  2. Transform Motion  a. where two plates slip past each other  b. creates strike-slip faults  c. blocks of crust slide horizontally past each other

 3. Convergent Motion  a. where two plates push together  b. reverse faults  c. blocks of crust pushed together, slide along reverse faults  4. Divergent Motion  a. two plates pull away from each other  b. creates normal faults  c. crust pulled away, slide along normal faults

 D. How Do Earthquake Waves Travel?  1. seismic Waves  a. waves of energy that travel through the Earth  b. body waves travel through interior of Earth  c. surface waves travel on earth’s surface  d. speed of wave depends on kind of material  2. P waves  a. travel through solids, liquids, gases  b. fastest waves  c. pressure waves  d. primary waves –first waves to be detected  e. move back and forth

 3. S waves  a. created when deformed waves spring back to original position  b. shear waves – second fastest  c. secondary waves –arrive after p waves  d. travel through solids and gases  4. Surface waves  a. move along Earth’s surface  b. produce motion in upper few kilometers  c. one type – back and forth motion  d. one type – up, down, and around motion  e. travel more slowly  f. cause more damage