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Earthquakes. An Earthquake is the sudden movement of the earth. It is caused by the abrupt release of strain that has accumulated over a long time. Earthquakes in History. Horses killed by a collapsing wall - San Francisco Earthquake 1906. San Francisco - 1906. Anchorage, Alaska - 1964.

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Presentation Transcript
an earthquake is the sudden movement of the earth
An Earthquake is the sudden movement of the earth
  • It is caused by the abrupt release of strain that has accumulated over a long time
earthquakes in history
Earthquakes in History

Horses killed by a collapsing wall - San Francisco Earthquake 1906

where earthquakes occur1
Where Earthquakes Occur
  • Most Earthquakes occur at the boundaries where tectonic plates meet
how earthquakes happen
How Earthquakes Happen
  • The crust may first bend, and then when stress exceeds the strength of the rocks, break and “snap” to a new position.
  • In the process, vibrations called “seismic waves” are generated.
three types of faults
Three Types of Faults

Strike-Slip

Thrust

Normal

strike slip fault example1
Strike-slip Fault Example

1906 San Francisco Earthquake

normal fault example
Normal Fault Example

Dixie Valley-Fairview Peaks, Nevada earthquake

December 16, 1954

severity of an earthquake
Severity of an Earthquake
  • The severity of an earthquake can be expressed in several ways:
magnitude
Magnitude
  • The measure of the amplitude of seismic waves
  • Expressed by the Richter Scale
  • Richter Earthquake Magnitudes Effects
  • Less than 3.5 Generally not felt, but recorded.
  • 3.5-5.4 Often felt, but rarely causes damage.
  • Under 6.0 At most slight damage to well-designed buildings. Can cause major damage to poorly constructed buildings over small regions.
  • 6.1-6.9 Can be destructive in areas up to about 100 kilometers across where people live.
  • 7.0-7.9 Major earthquake. Can cause serious damage over larger areas.
  • 8 or greater Great earthquake. Can cause serious damage in areas several hundred kilometers across.
magnitude richter scale
Magnitude – Richter Scale

Scale about 3.0

Scale about 6.0

Scale about 9.0

intensity
Intensity
  • A subjective measure that describes how strong a shock was felt at a particular location
  • Expressed by the Modified Mercalli Scale
what controls the level of shaking
What Controls the Level of Shaking?
  • Magnitude
    • More energy released
  • Distance
    • Shaking decays with distance
  • Local soils
    • amplify the shaking
earthquake effects ground shaking2
Earthquake Effects - Ground Shaking

KGO-TV News ABC-7

Loma Prieta, CA 1989

earthquake effects liquefaction
Earthquake Effects - Liquefaction

Source: National Geophysical Data Center

Niigata, Japan 1964

earthquake effects landslides
Earthquake Effects - Landslides

Turnnagin Heights,Alaska,1964

earthquake effects fires
Earthquake Effects - Fires

Loma Prieta, CA 1989

earthquake effects tsunamis
Earthquake Effects - Tsunamis

1957 Aleutian Tsunami

earthquake effects tsunamis1
Earthquake Effects - Tsunamis

Sumatra –Andaman Earthquake/Tsunami BEFORE

earthquake effects tsunamis3
Earthquake Effects - Tsunamis

Sumatra –Andaman Earthquake/Tsunami AFTER

earthquake effects tsunamis4
Earthquake Effects - Tsunamis

Sumatra –Andaman Earthquake/Tsunami AFTER

did you feel it
Did You Feel It?

http://earthquake.usgs.gov