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General Science. What is an Earthquake?. Earthquakes are one of the most powerful natural forces Shaking and vibration at the surface of the earth resulting from underground movement along a fault plane of from volcanic activity. Who Studies Earthquakes?. Seismologist study earthquakes

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General Science

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General Science


What is an Earthquake?

  • Earthquakes are one of the most powerful natural forces

  • Shaking and vibration at the surface of the earth resulting from underground movement along a fault plane of from volcanic activity


Who Studies Earthquakes?

  • Seismologist study earthquakes

  • Seismologists are trying to one day understand and predict earthquakes


Quick Fact

  • It is estimated that there are 500,000 detectable earthquakes in the world each year. 100,000 of those can be felt, and 100 of them cause damage.

  • Alaska is the most earthquake-prone state and one of the most seismically active regions in the world.


Review Plate Boundaries

  • To understand the causes of earthquakes you must understand Plate Boundaries

  • Plate Boundaries are the edges of the tectonic plates.

  • The point where two plates meet each other


Types of Stress Causing Earthquakes

  • Earthquakes occur because of stress because plates crash and slide against each other

  • Stress forces have exceeded the strength of the rock

  • The breaking of rock release huge amounts of energy in an earthquake


Earthquake Animation

The following animation shows a bird's eye view of a country road that cuts through an orchard. Passing right down the middle of the orchard, and across the road, is a fault zone. The animation shows how the earth is gradually distorted about the fault, in response to distant forces, eventually leading to sudden slip or displacement along the fault--what we call an earthquake.

Animation


Is this a Picture of a Fault or Fold?

Fault


What is a Fault?

  • A fault is a break in a mass of rock along which movement occurs

  • Many faults occur along boundaries

  • San Andreas Fault

    California


What is a Fold?

  • A fold is a bend in the layers of rock

  • Forms form where rock is squeezed together


Example California 1994

  • On January 17, 1994, Northridge, California

  • The earthquake measured 6.6 on the Richter scale.

  • This devastating event left "more than 50 dead

  • 5,900 injured

  • 20,000 homeless

  • 6 major freeways buckled

  • Countless businesses closed


Measuring an Earthquake

  • To measure a earthquake scientists use seismographs to record seismic waves

  • Seismic waves are created when rocks break and move and potential energy is transformed into kinetic in the form of waves


Seismic Graph

  • Seismographs detect the movement of the earth caused by these waves, and record their movement on paper


Richter Scale

  • The Richter scale rates earthquakes based on measurements of seismic waves.

  • It is only used when earthquakes are within 500Km if the Seismograph


Two Types of Energy Waves

  • When earthquakes occur they release energy in the forms of waves

  • The P (Primary)waves move in a up and down in a motion similar to the motion of a slinky,

  • S (secondary) waves move in a shear motion level to the direction the wave is traveling.


Tsunami

  • Tsunamis are large water waves, typically generated by seismic activity, that have historically caused significant damage to coastal communities throughout the world.


Can Scientists Predict Earthquake?

NO!

  • If scientist could predict earthquakes, Deaths would certainly be much fewer, and damage much less costly

  • So far no method has been proven accurate to predict earthquakes


How Many Earthquakes Have occurred this year?

  • 10

  • 100

  • 500

  • 1000+

  • 10,000

6,028

Located by the US Geological Survey National Earthquake Information Center


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