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EARTHQUAKES
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Earthquakes occur whenever there is __movement of the Earth’s__ ____Tectonic
Plates___________________________.
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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.