Earth quake


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Earth quake

  1. 1. Earthquakes are the shaking, rolling or sudden shock of the earth’s surface.  They are the Earth's natural means of releasing stress.  Earthquakes can be felt over large areas although they usually last less than one minute.  Earthquakes cannot be predicted, although scientists are working on it. 
  2. 2.  As the plates move they put forces on themselves and each other. When the force is large enough, the crust is forced to break. When the break occurs, the stress is released as energy, which moves through the Earth in the form of waves, which we feel and call an earthquake.
  3. 3. What is a fault? A fault is an area of stress in the earth where broken rocks slide past each other, causing a crack in the Earth's surface. There are 4 major types of faults which are as follows: dip-slip normal, dip-slip reverse, strike-slip, and oblique-slip.
  4. 4. Strike is long line, dip is short line Note the angle of dip given 45o Strike intersection w horizontal, dip perpendicular, angle from horizontal down toward surface
  5. 5. Divergent Convergent
  6. 6. Reverse Fault Quake - Japan DEMO – Types of faults Strike Slip Fault Quake - California Normal Fault Quake - Nevada
  7. 7. Earthquakes are caused by sudden release of accumulated strain energy along Faults Rocks on sides of fault are deformed by tectonic forces (((( ((( Rocks bend and store elastic energy Frictional resistance holding the rocks together is overcome by )))) )))
  8. 8. • Earthquakes often occur when tectonic plate collide • When two plates collide head-on, they push each other up and form mountains. That's how the Himalayas and other great mountain ranges (including the Rockies, long ago) were created. These zones mark of edges of tectonic plates
  9. 9.    Fires Liquifaction Landslides
  10. 10. •The point beneath the Earth's surface where the rocks break and move is called the focus of the earthquake. •The focus is the underground point of origin of an earthquake. Directly above the focus, on the Earth's surface, is the epicenter.
  11. 11. • Earthquake waves are known as seismic waves Seismometers instruments that record seismic waves Records the movement of Earth in relation to a stationary mass on a rotating drum or magnetic tape
  12. 12. The first kind of body wave is the P wave or primary wave. This is the fastest kind of seismic wave. The P wave can move through solid rock and fluids, like water or the liquid layers of the earth. It pushes and pulls the rock it moves through just like sound waves push and pull the air..
  13. 13. Love Waves The first kind of surface wave is called a Love wave, named after A.E.H. Love, a British mathematician who worked out the mathematical model for this kind of wave in 1911. It's the fastest surface wave and moves the ground from side-to-side. S WAVES (SURFACE WAVES) Rayleigh Waves The other kind of surface wave is the Rayleigh wave, named for John William Strutt, Lord Rayleigh, who mathematically predicted the existence of this kind of wave in 1885. A Rayleigh wave rolls along the ground just like a wave rolls across a lake or an ocean. Because it rolls, it moves the ground up and down, and side-to-side in the same direction that the wave is moving. Most of the shaking felt from an earthquake is due to the Rayleigh wave, which can be much larger than the other waves. (Theses produce all the damage!)
  14. 14. 2005
  15. 15. FACTORS EFFECTING THE DESTRUCTIVENESS OF AN EARTHQUAKE Magnitude The more energy released, the greater potential for damage, regardless of all other factors (and greater areal extent). Distance What Controls the Level of Shaking? Shaking decays with distance Local soils and bedrock geology Soil characteristics may amplify the shaking. (seasonal climatic variations can impact this) Complex geology tends to dampen waves
  16. 16. Earthquakes: Facts and Fiction  Fiction: Earthquakes usually happen in the morning. Fact: Earthquakes happen in both the day and the night. There is no pattern.  Fiction: There is such a thing as "earthquake weather." Fact: There is no connection between earthquakes and weather. Remember, earthquakes happen deep in the earth, far away from the weather!  Fiction: Earthquakes are on the increase. Fact: It may seem like we’re having more earthquakes because there are more reporting stations, but the truth is we’re not.  Fiction: We can prevent earthquakes from happening. Fact: No. You can protect yourself by doing things to secure buildings, like your home, but earthquakes can’t be prevented -- or predicted.