General Science

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 • 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. • 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? Fault

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

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 • 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 • 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? NO! • 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? • 10 • 100 • 500 • 1000+ • 10,000 6,028 Located by the US Geological Survey National Earthquake Information Center