1. General Science

2. What is an Earthquake?  Earthquakes are one of the most powerful natural forces  Shaking and vibration at the surface of the earth resulting from underground movement along a fault plane of from volcanic activity

3. Who Studies Earthquakes?  Seismologist study earthquakes  Seismologists are trying to one day understand and predict earthquakes

4. Quick Fact 1. It is estimated that there are 500,000 detectable earthquakes in the world each year. 100,000 of those can be felt, and 100 of them cause damage. 2. Alaska is the most earthquake-prone state and one of the most seismically active regions in the world.

5. Review Plate Boundaries  To understand the causes of earthquakes you must understand Plate Boundaries  Plate Boundaries are the edges of the tectonic plates.  The point where two plates meet each other

6. Types of Stress Causing Earthquakes  Earthquakes occur because of stress because plates crash and slide against each other  Stress forces have exceeded the strength of the rock  The breaking of rock release huge amounts of energy in an earthquake

7. Earthquake Animation The following animation shows a bird's eye view of a country road that cuts through an orchard. Passing right down the middle of the orchard, and across the road, is a fault zone. The animation shows how the earth is gradually distorted about the fault, in response to distant forces, eventually leading to sudden slip or displacement along the fault--what we call an earthquake.animation

8. Is this a Picture of a Fault or Fold?

9. What is a Fault?  A fault is a break in a mass of rock along which movement occurs  Many faults occur along boundaries  San Andreas Fault California California

10. What is a Fold?  A fold is a bend in the layers of rock  Forms form where rock is squeezed together

11. Example California 1994  On January 17, 1994, Northridge, California  The earthquake measured 6.6 on the Richter scale.  This devastating event left "more than 50 dead  5,900 injured  20,000 homeless  6 major freeways buckled  Countless businesses closed

13. Measuring an Earthquake  To measure a earthquake scientists use seismographs to record seismic waves  Seismic waves are created when rocks break and move and potential energy is transformed into kinetic in the form of waves

14. Seismic Graph  Seismographs detect the movement of the earth caused by these waves, and record their movement on paper

15. Richter Scale  The Richter scale rates earthquakes based on measurements of seismic waves.  It is only used when earthquakes are within 500Km if the Seismograph

16. Two Types of Energy Waves Two Types of Energy Waves  When earthquakes occur they release energy in the forms of waves  The P (Primary)waves move in a up and down in a motion similar to the motion of a slinky,  S (secondary) waves move in a shear motion level to the direction the wave is traveling.

17. Tsunami Tsunami  Tsunamis are large water waves, typically generated by seismic activity, that have historically caused significant damage to coastal communities throughout the world.

18. Can Scientists Predict Earthquake?  If scientist could predict earthquakes, Deaths would certainly be much fewer, and damage much less costly  So far no method has been proven accurate to predict earthquakes

19. How Many Earthquakes Have occurred this year? A.10 B.100 C.500 D.1000+ E.10,000 Located by the US Geological Survey National Earthquake Information Center