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EARTHQUAKES Earthquakes occur whenever there is __movement of the Earth’s__ ____Tectonic Plates___________________________. They occur along all types of ___Plate Boundaries____, and along ___faults (large fractures in the rock)___ within the plates. Structure of an Earthquake The ___Focus_or Hypocenter__ is the point underground where the earthquake originated. The ___Epicenter_____ is the point on the surface directly above the focus. __Elastic Rebound___ Theory- Explains how energy is spread during an earthquake. Types of Seismic Waves __P Waves__: “Primary” or “Push-Pull” waves, first to arrive (fastest waves), causes ground compression and expansion. __S Waves__: “Secondary” or “Shear” waves, travel half the speed of P waves, moves ground sideto-side and up-and-down. _Surface Waves_: Arrive last, travel the slowest, but cause the most ground movement and damage. Locating the Epicenter of an Earthquake The device that detects seismic activity is a ___Seismometer__ The paper that records the seismic activity is a __Seismogram___ In order to locate the Epicenter, you must have data from __at least 3_ Seismic Stations____ Earthquake intensity is measured using the ___Richter Scale___ Each number on the scale releases about 31 times* more energy than the previous number * So, an 8.0 earthquake releases 29,791 times more energy than a 5.0 Effects of an Earthquake ___Collapsed Buildings & Bridges___ ___Fires (from broken gas lines)_______ ____Landslides and Liquefaction_______ ___Tsunamis___ Studying Earth’s Interior We know the structure of Earth’s interior from studying the ___P and S waves__ of earthquakes __P Waves_ can travel through any material, but they bend when moving through liquid. This bending creates “___Shadow Zones__” __S Waves__ can only travel through solids, so they create a much larger “shadow zone” on the other side of Earth.