Earthquakes Liz LaRosa2009http://www.middleschoolscience.com What is an earthquake? TB pg. 211 Vibrations in the ground that result from movement along breaks in the earths lithosphere. Can also be caused by volcanic or magmatic activity Three Types of Faults, TB pg.213 Strike-Slip - Occurs on a transform boundary Reverse- Occurs on a convergent boundary Normal- Occurs 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 TB pg. 214 Focus point inside the Earth where an earthquake begins Epicenter point on Earths surface above focus How Seismographs or Seismometers Work, TB pg the pendulum remains Video link:cuLJLQground moves beneath it -measures ground motion and can be used to determine the distance seismic waves travel Typical Seismogram- a graphical illustration of EQ waves 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 Secondary Waves (S Waves) TB pg. 215 A type of seismic wave that moves the ground up and down or side to side Comparing Seismic Waves Surface Waves, TB pg. 215 Move along the Earths 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 Locating Earthquakes Locating Earthquakes 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-intensity- measures damage from shaking, I- XII Richter Scale How are Earthquakes Measured? Mercalli Intensity Scale Click Link for Interactive Demo San Francisco Earthquake, 1989 History Channel Video damage.jpg Earthquake Waves & Earths Interior Earthquake Risk-TB pg. 220 Tsunamis Brain POP-click on pic Formation of a tsunami Tsunami Warning System