• What are earthquakes?• What conditions cause earthquakes?• What are some vocabulary words associated with earthquakes?• How are earthquakes measured?• What are the results of earthquakes?• What does an earthquake feel like?
http://earthquake.usgs.gov/learn/kids/ Latest Quakes http://earthquake.usgs.gov/learn/today/Today in Earthquake History http://earthquake.usgs.gov/earthquakes/state s/georgia/history.php Georgia Earthquakes Click Past 8-30 days, too
1. The definition of an earthquake is… a sudden release of tectonic stress along a fault line. They can also result from volcanic activity. Earthquakes create vibrations that cause the breaking of rocks, violent shaking of Earth’s crust, and destruction of buildings.2. These vibrations move in all directions through the earth. They begin at a point along a fault.3. A fault is a break in earth’s crust.
• The earth’s crust is constantly experiencing pressure from forces within and around it. This pressure builds up over time, and eventually causes the crust to break. This becomes a fault.• Let’s experience it…
• Faults are divided into three main groups (WORKSHEET TIME!):4. Normal fault - when two plates are moving apart and one side of the fracture moves below the other; (caused by tension and occur at divergent boundaries!)5. Reverse fault or thrust fault - when two plates collide and one side of the fracture moves on top of another (caused by compression and occur at convergent boundaries!) A thrust fault has the same sense of motion as a reverse fault, but with the dip of the fault plane at less than 45 .6. Strike-slip or Lateral (football plays) - when two plates slide past each other horizontally. (caused by shear stress or shearing and occur at transform boundaries!) *Most common fault to cause an earthquake.*
7. Focus: An earthquake begins along a fault (a crack in the earth’s surface) at a point called the focus.8. Epicenter: Directly above the focus is a point on the earth’s surface called the epicenter.*E comes before F so the epicenter is above the focus.*
9. Seismic WavesWhen the fault ruptures with a suddenmovement energy is released that hasbuilt up over the years. The energyfrom an earthquake is released in theform of vibrations called seismicwaves… earthquakes! It is actuallywhen these seismic waves reach thesurface of the earth that most of thedestruction occurs, which we associatewith earthquakes.
Earthquake Waves10. Primary Wave (P-Wave) Three Main Types:•First set of waves•Move side to side•FASTEST wave11. Secondary Wave (S-Wave)•Second set of waves•Also, called a Shear Wave•Move up and down•Travel slow12. Surface Wave•Move up and down & side to side•MOST DANGEROUS•SLOWEST Wave
13. Magnitude is a number that characterizes the relative size of earthquakes & is proportional to energy released
What Kind Of Damage Do Earthquakes Cause? Earthquakes can also cause landslides, suddeneruptions as in the case of a hot lava flow from a volcano or giant waves called tsunamis. Sometimes new land mass are also formed. Such earthquakes are attributed with the creation of the greatest undersea mountainrange and the longest land mountain range. Liquefactionis also a danger of earthquakes in areas where the soil is wet or where water is nearby.14. Aftershocks are the small earthquakes thatfollow a larger one. They are the minorreadjustments along the fault after a quake. Withtime, these small quakes get less and lessintense.
15. Liquefaction- When water-saturated soil is shaken in an earthquake, it can behave like a liquid. This is called liquefaction.• When the soil acts like a liquid, it can cause great damage to the buildings standing on it.• Liquefaction is what happens to the wet sand at the beach. The sand is hard when you stand on it, but becomes liquid-like when you stick your toes down in it. *See the cornstarch demonstration*
16. Deformation• the change in the shape of rock as a result of stress
Folding17. Folding-the bending of the rock layers from stress is called folding.18. Anticline-folds that arch up19. Syncline-folds that sink down
20. Elastic Deformation- Leads to earthquakes; it is the sudden return of elastically deformed rock to its undeformed shape• Think of it as a stretched-out rubber band. You can only stretch it so far before it breaks. When it breaks, it releases energy. Then the unbroken pieces return to their original shape.• (from the textbook)
• 9.5 Chile, May 22, 1960• 9.2 Indian Ocean (Sumatra tsunami) Dec 26,2004• 9.2 Prince William Sound, Alaska, March 28, 1964• 9.1 Andreanof Islands, Aleutian Islands, Pacific,• March 9, 1957• 9.0 Great East Japan Earthquake and Tsunami, March 13, 2011• 9.0 Kamchatka, Russia, November 4, 1952• 8.8 Off the Coast of Ecuador, January 31, 1906• 8.7 Rat Islands, Aleutian Islands, Pacific,• February 4, 1965• 8.6 India-China Border, August 15, 1950• 8.5 Kamchatka, Russia, February 3, 1923• 8.5 Banda Sea, Indonesia, February 1, 1938• 8.5 Kuril Islands, Pacific, October 13, 1963• http://www.bbc.co.uk/news/world-asia-pacific-12725646
• In the lower 48 states, there is a tie between the February 1812, New Madrid, Missouri earthquake and the January 1857, Fort Tejon, California earthquake--both magnitude 7.9--for the strongest earthquake recorded.
• Generally, during an earthquake you first will feel a swaying or small jerking motion, then a slight pause, followed by a more intense rolling or jerking motion. The duration of the shaking you feel depends on the earthquakes magnitude, your distance from the epicenter, and the geology of the ground under your feet.
• For minor earthquakes, ground shaking usually lasts only a few seconds.• Strong shaking from a major earthquake usually lasts less than one minute. For example, shaking in the 1989 magnitude 7.1 Loma Prieta (San Francisco) earthquake lasted 15 seconds;• For the 1906 magnitude 8.3 San Francisco earthquake it lasted about 40 seconds.• Shaking for the 1964 magnitude 9.2 Alaska earthquake, however, lasted three minutes.