FaultingFaulting

AndAnd

EarthquakesEarthquakes

Forces Inside EarthForces Inside Earth

Objectives:Objectives: Explain how earthquakes result from the Explain how earthquakes result from the

buildup of three different stresses in Earth’s buildup of three different stresses in Earth’s crustcrust

Describe Describe normal, reverse, and strike-slip normal, reverse, and strike-slip faultsfaults

Causes of EarthquakesCauses of Earthquakes

Passing the Elastic Limit Causes FaultingPassing the Elastic Limit Causes Faulting Applied stresses can cause rocks to bend and Applied stresses can cause rocks to bend and

stretch stretch Eventually rocks will break away from one Eventually rocks will break away from one

anotheranotherArea in which the rocks break and move is Area in which the rocks break and move is

called a called a faultfaultVibrations and shaking of the Earth’s crust is Vibrations and shaking of the Earth’s crust is

called an earthquakecalled an earthquake Earth’s crust movement causes the stresses Earth’s crust movement causes the stresses

appliedapplied

Types of FaultsTypes of Faults

Normal Fault Normal Fault from from Tension/Pulling ApartTension/Pulling Apart Earth’s plates move apartEarth’s plates move apart Movement of the plates causes Movement of the plates causes tensiontension Rocks above the fault surface move Rocks above the fault surface move

downward in relation to the rocks below the downward in relation to the rocks below the fault surfacefault surface

Types of FaultsTypes of Faults

Reverse Faults Reverse Faults from from Compression/SqueezingCompression/Squeezing Compression forces are applied because Compression forces are applied because

Earth’s plates are coming togetherEarth’s plates are coming together Causes rocks to bend and breakCauses rocks to bend and break Rocks above the fault surface are forced up Rocks above the fault surface are forced up

and over the rocks below the fault surfaceand over the rocks below the fault surface

Types of FaultsTypes of Faults

Strike-slip Fault Strike-slip Fault fromfrom Shearing/ sliding or Shearing/ sliding or slipping pastslipping past Earth’s plates move sideways to one anotherEarth’s plates move sideways to one another Creates a shear forceCreates a shear force Rocks on either side of the fault surface are Rocks on either side of the fault surface are

moving past each other without much upward moving past each other without much upward or downward movementor downward movement

Causes of the Stress ForcesCauses of the Stress Forces

VolcanoesVolcanoes Collapsing of cavernsCollapsing of caverns Plate TectonicsPlate Tectonics

Convergent boundaryConvergent boundary Divergent boundaryDivergent boundary Strike Slip boundaryStrike Slip boundary

Earthquake InformationEarthquake Information ObjectivesObjectives

Compare and contrast primary, Compare and contrast primary, secondary, and surface wavessecondary, and surface waves

Explain how an earthquake epicenter Explain how an earthquake epicenter is located using seismic wave is located using seismic wave informationinformation

Describe how seismic wave studies Describe how seismic wave studies indicate the structure of Earth’s indicate the structure of Earth’s interiorinterior

Types of Seismic WavesTypes of Seismic Waves

Focus – the point in Earth’s interior where the Focus – the point in Earth’s interior where the energy waves are producedenergy waves are produced

Epicenter -Epicenter -The point on Earth’s surface The point on Earth’s surface directly above the earthquake focusdirectly above the earthquake focus

Seismic wave - the energy waves that move Seismic wave - the energy waves that move outward from the earthquake focus and make outward from the earthquake focus and make the ground quakethe ground quake

Types of Seismic WavesTypes of Seismic Waves

Seismic WavesSeismic Waves Primary waves like a slinkyPrimary waves like a slinky

Energy waves that cause rocks to move Energy waves that cause rocks to move back and forth in the same directionback and forth in the same direction

Compression and stretching forces are Compression and stretching forces are createdcreated

Secondary waves whipping a ropeSecondary waves whipping a ropeEnergy waves that cause rocks to move at Energy waves that cause rocks to move at

right angles to the waveright angles to the wave

Types of Seismic WavesTypes of Seismic Waves

Surface waves like ocean wavesSurface waves like ocean wavesEnergy waves that reach the Earth’s Energy waves that reach the Earth’s

surfacesurfaceEnergy waves that move rocks in an Energy waves that move rocks in an

elliptical motionelliptical motion

Locating an EpicenterLocating an Epicenter

Seismic waves do not travel through Seismic waves do not travel through earth’s surface at the same speedearth’s surface at the same speed Primary waves are the fastestPrimary waves are the fastest Surface waves are the slowestSurface waves are the slowest

Seismograph stationsSeismograph stations Record the information from the earthquake Record the information from the earthquake

by recording the different types of waves as by recording the different types of waves as they reach the stationthey reach the station

Locating and EpicenterLocating and Epicenter

Epicenter LocationEpicenter Location If information is received from the earthquake If information is received from the earthquake

at three stations, then the epicenter can be at three stations, then the epicenter can be locatedlocated

A circle is drawn around each station on a A circle is drawn around each station on a mapmapThe radius is equal to the distance from the The radius is equal to the distance from the

station to the epicenterstation to the epicenter The point in which all three circles intersect is The point in which all three circles intersect is

the earthquake epicenterthe earthquake epicenter

Using Seismic Waves to Map Using Seismic Waves to Map Earth’s InteriorEarth’s Interior

The speed of the waves changes as the The speed of the waves changes as the depth changesdepth changes The speed changes in accordance to the The speed changes in accordance to the

density of the layers of Earthdensity of the layers of Earth

Using Seismic Waves to Map Using Seismic Waves to Map Earth’s InteriorEarth’s Interior

Structure of EarthStructure of Earth Inner coreInner core

Solid innermost layerSolid innermost layer and very dense and very denseComposed of mostly nickel and ironComposed of mostly nickel and iron

Outer coreOuter coreLiquid layer Liquid layer that surrounds the inner corethat surrounds the inner coreComposed of nickel and ironComposed of nickel and iron

Using Seismic Waves to Map Using Seismic Waves to Map Earth’s InteriorEarth’s Interior

MantleMantleLargest layer located above the inner coreLargest layer located above the inner coreComposed of silicon, oxygen, magnesium, Composed of silicon, oxygen, magnesium,

and ironand iron CrustCrust

Outermost layerOutermost layerSolid and similar in composition to the Solid and similar in composition to the

mantle, mainly silicon and oxygenmantle, mainly silicon and oxygen

Using Seismic Waves to Map Using Seismic Waves to Map Earth’s InteriorEarth’s Interior

Moho DiscontinuityMoho Discontinuity Moho’s Boundary Moho’s Boundary between the crust and the between the crust and the

mantlemantle Seismic waves speed up as they reach this Seismic waves speed up as they reach this

areaarea Seismic waves speed up as they reach more Seismic waves speed up as they reach more

dense areas and slow down when the reach less dense areas and slow down when the reach less dense areasdense areas The more solid the layer the more denseThe more solid the layer the more dense

Using Seismic Waves to Map Using Seismic Waves to Map Earth’s InteriorEarth’s Interior

Shadow zoneShadow zone The area between 105-140 degrees from the The area between 105-140 degrees from the

epicenterepicenter Area in which seismic waves can’t be detectedArea in which seismic waves can’t be detected What is the cause?What is the cause?

Secondary waves can’t be transmitted Secondary waves can’t be transmitted through liquid layersthrough liquid layers

Primary waves are slowed and deflected by Primary waves are slowed and deflected by the outer core and speed up again when the the outer core and speed up again when the reach the solid inner corereach the solid inner core

Destruction by EarthquakesDestruction by Earthquakes

ObjectivesObjectives Define magnitude and Richter scaleDefine magnitude and Richter scale List ways to make your classroom and home List ways to make your classroom and home

more earthquake safemore earthquake safe

Measuring EarthquakesMeasuring Earthquakes

SeismologySeismology Seismologists - People who study earthquakes and Seismologists - People who study earthquakes and

seismic wavesseismic waves Use instruments called seismographsUse instruments called seismographs

Record seismic wavesRecord seismic wavesA drum with a sheet of paper vibrates and a A drum with a sheet of paper vibrates and a

stationary pen marks the vibrations on the paperstationary pen marks the vibrations on the paperThe height of the lines are used to measure the The height of the lines are used to measure the

energy released from the earthquake called the energy released from the earthquake called the magnitudemagnitude

Measuring EarthquakesMeasuring Earthquakes

Earthquake MagnitudeEarthquake Magnitude Usually determines the strength of the breakUsually determines the strength of the break Doesn’t determine the duration or the sizeDoesn’t determine the duration or the size For each increase of 1is 10 times strongerFor each increase of 1is 10 times stronger

An earthquake of 4 is 10 times stronger than an An earthquake of 4 is 10 times stronger than an earthquake of 3earthquake of 3

TsunamisTsunamis

Caused by the movement of the ocean floorCaused by the movement of the ocean floor Causes a disruption in the waterCauses a disruption in the water Some are so wide that a large ship can travel Some are so wide that a large ship can travel

over the wave without knowingover the wave without knowing Recent earthquake in the Indian Ocean Recent earthquake in the Indian Ocean

created a tsunamis that was 100 feet high and created a tsunamis that was 100 feet high and moving at 500 mphmoving at 500 mph

Earthquake SafetyEarthquake Safety

Quake proofing your homeQuake proofing your home Place heavy objects near the floorPlace heavy objects near the floor Fix gas appliances in placeFix gas appliances in place

9.4 Living on a Fault9.4 Living on a Fault

ObjectivesObjectives Recognize that most loss of life in an Recognize that most loss of life in an

earthquake is caused by the destruction of earthquake is caused by the destruction of human-made structureshuman-made structures

Consider who should pay for making Consider who should pay for making structures seismic safestructures seismic safe

Who should pay for earthquake Who should pay for earthquake preparation?preparation?

Seismic safe structuresSeismic safe structures Structures that are resistant to the vibrations Structures that are resistant to the vibrations

of Earth’s crustof Earth’s crust Structures are made with mooringsStructures are made with moorings

Made of steel and are filled with alternating Made of steel and are filled with alternating layers of rubber and steellayers of rubber and steel

These structures absorb the energy These structures absorb the energy produced from the earthquakeproduced from the earthquake

What is an Earthquake Short What is an Earthquake Short VideoVideo

http://www.sciencekids.co.nz/videos/earth/whatisanearthquake.html

Earthquake Long VideoEarthquake Long Video

http://video.pbs.org/video/1690329036/http://video.pbs.org/video/1690329036/