FaultFault – a fracture or break in the– a fracture or break in the
Earth’s lithosphereEarth’s lithosphere
Rock along one side of a faultRock along one side of a fault
can move up, down, or sidewayscan move up, down, or sideways
in relation to rock along thein relation to rock along the
other side of the fault.other side of the fault.
How faults formHow faults form
Forces cause rocks to bend & stretchForces cause rocks to bend & stretch
Stress is the force exerted when a rockStress is the force exerted when a rock
presses on, pulls on, or pushes againstpresses on, pulls on, or pushes against
another rockanother rock
As stress increases, the rocks mayAs stress increases, the rocks may
The break in the rock causes faults toThe break in the rock causes faults to
EarthquakeEarthquake – the vibrations or– the vibrations or
sudden movements produced bysudden movements produced by
the breaking of rock.the breaking of rock.
Most earthquakes result fromMost earthquakes result from
rocks moving over, under, orrocks moving over, under, or
past each other along faultpast each other along fault
How do earthquakes actuallyHow do earthquakes actually
As rocks (plates) move pastAs rocks (plates) move past
each other along a fault, theireach other along a fault, their
rough surfaces catch,rough surfaces catch,
temporarily stoppingtemporarily stopping
EarthquakesEarthquakes Forces keep driving the rocks to move,Forces keep driving the rocks to move,
and stress builds up.and stress builds up.
The stress causes the rocks to bend andThe stress causes the rocks to bend and
change shape, eventually breaking andchange shape, eventually breaking and
causing an earthquake.causing an earthquake.
The strength of an earthquakeThe strength of an earthquake
depends on: the amount of stressdepends on: the amount of stress
that builds & the distance the rocksthat builds & the distance the rocks
move along the faultmove along the fault
Types of FaultsTypes of Faults
Three types of forces –normal,Three types of forces –normal,
reverse, & strike-slip faultsreverse, & strike-slip faults
Normal – pulls rocks apartNormal – pulls rocks apart
Reverse – squeezes rocks togetherReverse – squeezes rocks together
Strike-slip – causes rocks to slideStrike-slip – causes rocks to slide
past each otherpast each other
Normal FaultsNormal Faults
A break in rock caused byA break in rock caused by
tension forcestension forces..
Rock above the fault surfaceRock above the fault surface
movesmoves downwarddownward in relation toin relation to
rock below the fault surface.rock below the fault surface.
Reverse FaultsReverse Faults
A break in the rock caused byA break in the rock caused by
compression forces.compression forces.
The rock above the fault planeThe rock above the fault plane
movesmoves upwardupward relative to therelative to the
rock below the fault surface.rock below the fault surface.
Strike-Slip FaultsStrike-Slip Faults
ShearShear forces push on rock inforces push on rock in
Rocks on either side of the faultRocks on either side of the fault
movemove past each otherpast each other (without(without
much upward or downwardmuch upward or downward
Ex. San Andreas FaultEx. San Andreas Fault
Energy from Earthquakes Travels
Waves carryWaves carry energyenergy!!!!
The energy from an earthquakeThe energy from an earthquake
travels astravels as seismic wavesseismic waves, which, which
cause the vibrations during ancause the vibrations during an
Focus & Epicenter
TheThe focusfocus of an earthquake is the pointof an earthquake is the point
underground where rocks 1underground where rocks 1stst
begin to move.begin to move.
TheThe epicenterepicenter is the point on Earth’s surfaceis the point on Earth’s surface
directly above the focus.directly above the focus.
Primary WavesPrimary Waves
P wavesP waves
FastestFastest seismic wavesseismic waves
to reach any location after anto reach any location after an
Can travel throughCan travel through solids,solids,
liquids, and gasesliquids, and gases
Secondary WavesSecondary Waves
wave to arrive at any locationwave to arrive at any location
Travel atTravel at ½ the speed of P waves½ the speed of P waves
Can travel throughCan travel through solidsolid (rocks) but(rocks) but
NOT throughNOT through liquid and gasesliquid and gases
Surface WavesSurface Waves
Move alongMove along Earth’s surfaceEarth’s surface, but, but
NOT through its’NOT through its’ interiorinterior
Causes the largestCauses the largest groundground
movementsmovements & the most& the most damagedamage
They make the groundThey make the ground roll up &roll up &
downdown OROR shake from side to sideshake from side to side
Damage from EarthquakesDamage from Earthquakes
TheThe Richter scaleRichter scale measures anmeasures an
earthquake’s magnitude based onearthquake’s magnitude based on
how fast the ground moves at thehow fast the ground moves at the
seismic station.seismic station.
SeismographSeismograph – the instrument that– the instrument that
constantly records groundconstantly records ground
movement . Used to measuremovement . Used to measure
magnitude of an earthquake.magnitude of an earthquake.
Tsunami – is a water wave triggered by anTsunami – is a water wave triggered by an
earthquake, volcanic eruption, or landslide.earthquake, volcanic eruption, or landslide.
They are sometimes called tidal wavesThey are sometimes called tidal waves
May not be a single wave, but can be severalMay not be a single wave, but can be several
waves with different heights and can arrivewaves with different heights and can arrive
hours apart.hours apart.
They move quickly and can travel thousandthsThey move quickly and can travel thousandths
of kilometers without weakening. Speeds canof kilometers without weakening. Speeds can
reach 430 mi/hr.reach 430 mi/hr.
Liquefaction – the process in whichLiquefaction – the process in which
shaking of the ground causes soil to act likeshaking of the ground causes soil to act like
a liquid.a liquid.
For a short time the soil acts like thickFor a short time the soil acts like thick
It only occurs in areas where the soil isIt only occurs in areas where the soil is
made up of loose sand and silt andmade up of loose sand and silt and
contains a large amount of water.contains a large amount of water.