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Transcript
Earthquakes Liz LaRosa http://www.middleschoolscience.com 2009 What is an earthquake? TB pg. 211 • Vibrations in the ground that result from movement along breaks in the earth’s lithosphere. • Can also be caused by volcanic or magmatic activity Three Types of Faults, TB pg.213 ReverseOccurs on a convergent boundary Strike-SlipOccurs on a transform boundary NormalOccurs on a divergent boundary What causes earthquakes? TB pg. 213 • Tectonic plates move past each other causing stress. Stress causes the rock to deform – Plastic deformation – does not cause earthquakes – Elastic deformation – rock stretches then reaches a breaking point, releasing energy. Elastic Rebound – deformed rock goes back to its original shape http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM TB pg. 214 Focus – point inside the Earth where an earthquake begins Epicenter – point on Earth’s surface above focus How Seismographs or Seismometers Work, TB pg. 217 -measures ground motion and can be used to determine the distance seismic waves travel the pendulum remains Video link: http://www.cleanvideosearch.com/media/action/yt/watch?v=Gbd1F cuLJLQground moves beneath it http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM Typical Seismograma graphical illustration of EQ waves http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt Primary Waves (P Waves) TB pg. 215 • A type of seismic wave that compresses and expands the ground • The first wave to arrive at an earthquake http://daphne.meccahosting.com/~a0000e89/insideearth2.htm Secondary Waves (S Waves) TB pg. 215 • A type of seismic wave that moves the ground up and down or side to side http://daphne.meccahosting.com/~a0000e89/insideearth2.htm Comparing Seismic Waves Surface Waves, TB pg. 215 • Move along the Earth’s surface • Produces motion in the upper crust – Motion can be up and down or rolling motion – Travel more slowly than S and P waves • More destructive How do scientists calculate how far a location is from the epicenter of an earthquake? • Scientists calculate the difference between arrival times of the P waves and S waves-use 3 seismic stations • Triangulation locates the earthquakes epicenter Locating Earthquakes http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM Locating Earthquakes http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM Locating Earthquakes http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM How are Earthquakes Measured? 3 Scales are used: Richter Scale-magnitude-from 0-no limit, amount of ground motion Moment magnitude-magnitude— total amount of energy in EQ Modified Mercalli Scale-intensitymeasures damage from shaking, IXII Richter Scale How are Earthquakes Measured? Mercalli Intensity Scale Click Link for Interactive Demo http://elearning.niu.edu/simulations/images/S_portfolio/Mercalli/Mercalli_Scale.swf San Francisco Earthquake, 1989 History Channel Video http://www.history.com/topics/1989-san-francisco-earthquake http://www.civildefence.govt.nz/assets/Uploads/images/raildamage.jpg Earthquake Waves & Earth’s Interior Earthquake Risk-TB pg. 220 Tsunamis Brain POP-click on pic http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM Formation of a tsunami http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt Tsunami Warning System http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt
