General ScienceGeneral Science

What is an Earthquake?What is an Earthquake?

Earthquakes are one of Earthquakes are one of the most powerful the most powerful natural forcesnatural forces

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

Who Studies Earthquakes?Who Studies Earthquakes?

Seismologist study Seismologist study earthquakesearthquakes

Seismologists are trying Seismologists are trying to one day understand to one day understand and predict and predict earthquakesearthquakes

Quick FactQuick Fact1.1. It is estimated that It is estimated that

there are there are 500,000 500,000 detectable detectable earthquakesearthquakes in the in the world each year. world each year. 100,000 of those can 100,000 of those can be felt, and 100 of be felt, and 100 of them cause damage. them cause damage.

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

Review Plate BoundariesReview Plate Boundaries To understand the To understand the

causes of causes of earthquakes you earthquakes you must understand must understand Plate BoundariesPlate Boundaries

Plate Boundaries are Plate Boundaries are the edges of the the edges of the tectonic plates. tectonic plates.

The point where two The point where two plates meet each plates meet each otherother

Types of Stress Causing Types of Stress Causing EarthquakesEarthquakes

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

Stress forces have Stress forces have exceeded the exceeded the strength of the rockstrength of the rock

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

Earthquake AnimationEarthquake 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.

Is this a Picture of a Is this a Picture of a Fault or Fold?Fault or Fold?

What is a Fault?What is a Fault?

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

Many faults occur Many faults occur along boundariesalong boundaries

San Andreas FaultSan Andreas Fault

CaliforniaCalifornia

What is a Fold?What is a Fold?

A fold is a A fold is a bend in the bend in the layers of layers of rockrock

Forms form Forms form where rock where rock is squeezed is squeezed togethertogether

Example California 1994Example California 1994

On January 17, 1994, On January 17, 1994, Northridge, CaliforniaNorthridge, California

The earthquake The earthquake measured 6.6 on the measured 6.6 on the Richter scale. Richter scale.

This devastating event This devastating event left "more than 50 deadleft "more than 50 dead

5,900 injured5,900 injured 20,000 homeless20,000 homeless 6 major freeways buckled6 major freeways buckled Countless businesses Countless businesses

closedclosed

Measuring an EarthquakeMeasuring an Earthquake

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

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

Seismic GraphSeismic Graph

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

Richter ScaleRichter Scale

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

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

Two Types of Energy Two Types of Energy WavesWaves When earthquakes occur they release When earthquakes occur they release

energy in the forms of wavesenergy in the forms of waves The P (Primary)waves move in a up and The P (Primary)waves move in a up and

down in a motion similar to the motion of down in a motion similar to the motion of a slinky, a slinky,

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

TsunamiTsunami Tsunamis are large Tsunamis are large

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

Can Scientists Predict Can Scientists Predict Earthquake?Earthquake?

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

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

How Many Earthquakes How Many Earthquakes Have occurred this year?Have occurred this year?

A. 10

B. 100

C. 500

D. 1000+

E. 10,000

Located by the US Geological Survey National Earthquake Information Center