Features of earthquakes
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Features of Earthquakes. Origin of Seismic Waves. Moving rocks get caught on each other at faults Stress builds up until elastic limit is passed Built-up energy is released at the focus

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Origin of seismic waves
Origin of Seismic Waves

  • Moving rocks get caught on each other at faults

  • Stress builds up until elastic limit is passed

  • Built-up energy is released at the focus

  • Seismic waves are produced & travel outward from focus


3 types of seismic waves
3 types of seismic waves

  • Primary

  • Secondary

  • Surface


Primary or p waves
Primary or P-waves

  • Particles in rocks move back and forth in same direction that wave is traveling

  • Fastest


Secondary or s waves
Secondary or S-waves

  • Particles in rocks move at right angles to direction wave is traveling

  • Slower


Surface waves
Surface Waves

  • Particles in rocks move in a backward rolling motion & side to side swaying

  • Slowest

  • Most destructive



Locating the epicenter
Locating the epicenter

  • Seismologists take seismograms from 3 different seismograph locations.

  • They use these to determine the distance to the epicenter of each station.

  • Then they draw a circle around each station with the distance as a radius.

  • Point where all 3 intersect is the epicenter.



Basic structure of earth
Basic Structure of Earth

  • Crust

  • Upper mantle

  • Lower mantle

  • Outer core

  • Inner core


Crust
Crust

  • Outermost layer

  • Thickness varies 5 -60 km

  • More silicon & aluminum

  • Less magnesium & iron

  • Less dense than mantle


Upper mantle
Upper Mantle

  • Contains the asthenosphere

  • Weak rock flows slowly


Lower mantle
Lower mantle

  • Made of silicon, oxygen, magnesium, & iron


Outer core
Outer Core

  • Liquid made mostly of iron


Inner core
Inner Core

  • Solid

  • Dense

  • Mostly iron with nickel, oxygen, silicon,& sulfur

  • Pressure keeps it solid


Shadow zone
Shadow Zone

  • area where NO seismic waves are detected

  • Primary are slowed and bent but not stopped

  • Secondary are not transmitted through the liquid outer core


Moho

  • Boundary between crust and upper mantle (Mohorovicic discontinuity)


Speed of seismic waves
Speed of Seismic Waves

  • Seismic waves speed up through bottom of crust & upper mantle

  • Primary and Secondary slow down in asthenosphere

  • Gains speed in solid part of mantle

  • Secondary stops in liquid outer core

  • Primary slow in outer core and speed up in solid inner core


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