Transcript Earthquakes
Earthquakes! **Adapted from www.middleschoolscience.com What is an earthquake? • Used to describe both sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip • Caused by volcanic or magma activity, • Caused by other sudden stress changes in the earth. Three Types of Faults Strike-Slip Thrust Normal What causes earthquakes? • Tectonic plates move past each other causing stress. Stress causes the rock to deform, break, and/or move Elastic Rebound – deformed rock goes back to its original shape http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM Focus – point inside the Earth where an earthquake begins Epicenter – point on Earth’s surface above focus How Seismographs Work the pendulum remains fixed as the ground moves beneath it http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM Typical Seismogram http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt Primary Waves (P Waves) • PUSH-PULL PATTERN! – A type of seismic wave that pushes & pulls the ground • The FIRST wave to arrive from an earthquake—travels the fastest! • Travels Parallel to the direction the wave travels http://daphne.meccahosting.com/~a0000e89/insideearth2.htm Secondary Waves (S Waves) • A type of seismic wave that moves the ground up and down or side-to-side (perpendicular) to the direction the wave travels • Slower! • More destructive to buildings http://daphne.meccahosting.com/~a0000e89/insideearth2.htm Comparing Seismic Waves **P & S Wave song: http://www.youtube.com/watch?v=w3NLexYxR7g Surface Waves • Move along the Earth’s surface – ROLL OUT! Motion can be up and down, around & back & forth • Travel more slowly than S and P waves – Last to arrive • Most destructive to structures 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 • The further away an earthquake is, the greater the time between the arrival of the P waves and the S waves 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? Richter Scale How are Earthquakes Measured? Modified Mercalli Intensity Scale Click Link for Interactive Demo http://elearning.niu.edu/simulations/images/S_portfolio/Mercalli/Mercalli_Scale.swf Earthquake Waves & Earth’s Interior **See how seismic waves move through the Earth’s layers here (Shadow zone): http://www.classzone.com/books/earth_science/terc/content/visualizations/es1009/es1009page01.cfm Seismic Waves in the Earth http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM Tsunamis 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