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EARTHQUAKES
- A.Sudden vibration of the earth caused by release of energy
- B.Most earthquakes are generated by movement along fault
- C. Focus-area insdie the earth where the energy is released
- 1.Shallow focus earthquakes-occur less than 40 miles within the earth
- 2. Deep focus earthquakes- occur greaer than 180 miles within the earth
- D. Epicenter-location on Earths surface directly above the focus
- E.Foreshocks-smaller earthquakes that preced a larger earthquake
- F. Aftershocks-smaller earthquakes that follow a large earthquake
- G.Elastic Rebound Theory
- 1. Rocks along an active fault plane stick
- 2.Rocks on either side of fault slowly bend and store energy
- 3.Eventually internal strength of rocks along fault plane are exceeded and they rupture
- 4.Rocks on either side of fault plane "snap back" to their original position, releasing energy that radiates all directions
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Seismology
- A. STUDY OF EARTHQUAKE WAVES
- B.TYPES OF SEISMOGRAPHS
- 1. Vertical motion detector
- 2. Horizontal motion detector
- C. SEISMORGRAM-seismograph record
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EARTHQUAKE WAVES
- A. BODY WAVES-move through the Earths interior
- 1.P-waves
- a. Arrive first at seismic recording station
- b. Rocks expand and contract as waves move through them
- c. Travel through solids, liquids, and gases
- 2. S-waves
- a. Arrive second at a recording station
- b. Shake rocks at right angles to their direction of travel
- c. Travel only through solids
- B.SURFACE WAVES-travel along Earths surface
- 1. Cause much of the damage associaed with earthquakes
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Locating Earthquakes
look at page 101!!!
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Measuring Earthquakes
- A. MODIFIED MERCALLI INTENSITY SCALE
- 1.Measures damage done and peoples reactions to earthquakes
- 2. Used primarily by insurace companies
- B. RICHTER SCALE
- 1. Magnitude scale that measures amplitude of the largest wave recorded
- 2. The difference between any two numberes represents a 32 fold increase in energy released
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Damages Associated with Earthquakes
- A. GROUND SHAKING- causes the most damage and loss of life
- 1. Geology and ground shaking
- a. Solid bedrock-structures built on solid bedrock generally suffer less damage
- b. Liquefaction- water saturated sediment may lose cohesion when shaken and flow
- 2. Building materials and ground shaking
- a. Wood and reinforced concrete tend to be more flexible
- b. Brick and unreinforced concrete tend to crumble
- B. TSUNAMI
- 1. Series of waves generated by earthquakes , volcanic eruptions, underwater landslides
- 2. Are 3-6 feet high when travel across ocean
- 3. As waves enter shallow water, they slow and begin to build
- 4.Tsunami may come onshore as waves or as rapid rise in water
- C. LANDSLIDES- vibrations frm earthquakes may generate mass wasting events
- D. GROUND SUBSIDENCE-ground surface may subside due to movement along faults
- E. FIRE
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