EARTHQUAKES AND PLATE TECTONICS CHAPTER 6 SECTION 1.
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Transcript of EARTHQUAKES AND PLATE TECTONICS CHAPTER 6 SECTION 1.
EARTHQUAKES AND PLATE TECTONICS
CHAPTER 6 SECTION 1CHAPTER 6 SECTION 1
ELASTIC REBOUND ELASTIC REBOUND THEORYTHEORY
Rocks on each side of a fault are moving.Rocks on each side of a fault are moving.
Fault is locked, rocks stop moving.Fault is locked, rocks stop moving.
Rocks on each side of a fault are stressed.Rocks on each side of a fault are stressed.
Rocks fracture and separate at weakest point.Rocks fracture and separate at weakest point.
Rocks return to original shape.Rocks return to original shape.
Elastic Rebound TheoryElastic Rebound Theory
AFTERSHOCKSAFTERSHOCKS
Original earthquake releases energy in Original earthquake releases energy in the form of vibrations called seismic the form of vibrations called seismic waves.waves.
These vibrations may increase stress in These vibrations may increase stress in other rocks along the fault.other rocks along the fault.
The increased stress on these rocks may The increased stress on these rocks may cause them to fracture and spring back.cause them to fracture and spring back.
The series of smaller tremors are called The series of smaller tremors are called aftershocks. aftershocks.
FOCUSFOCUS
Area along a fault where the slippage first Area along a fault where the slippage first occursoccurs
Focus is beneath the earth’s surfaceFocus is beneath the earth’s surface
The epicenter is directly aboveThe epicenter is directly above
The depth of the focus variesThe depth of the focus varies
FOCUS DEPTH - 1975-95FOCUS DEPTH - 1975-95
FOCUS DEPTH OF FOCUS DEPTH OF EARTHQUAKES IN EARTHQUAKES IN
WASHINGTON 1977-1996WASHINGTON 1977-1996
EPICENTEREPICENTER
A point on the earth’s A point on the earth’s surface directly above the surface directly above the focusfocus
MAJOR EARTHQUAKE MAJOR EARTHQUAKE ZONESZONES
Pacific Ring of FirePacific Ring of Fire
Mid-ocean ridgesMid-ocean ridges
Eurasian-Melanesian Mountain BeltEurasian-Melanesian Mountain Belt
MAJOR EARTHQUAKES MAJOR EARTHQUAKES AREASAREAS
PUGET SOUND FAULT PUGET SOUND FAULT ZONESZONES
MagnitudeMagnitude
STRUCTURAL DAMAGESTRUCTURAL DAMAGEKobe EarthquakeKobe Earthquake
LIQUEFACTIONLIQUEFACTIONKobeKobe
RECORDING EARTHQUAKESRECORDING EARTHQUAKES
CHAPTER 6, SECTION 2CHAPTER 6, SECTION 2
TYPES OF SEISMIC WAVESTYPES OF SEISMIC WAVES
P wavesP waves
S wavesS waves
L wavesL waves
P WAVESP WAVES
Fastest waveFastest waveFirst recorded on seismographFirst recorded on seismographTravel through solid and liquidTravel through solid and liquidCause rock particles to move together and Cause rock particles to move together and
apart along the direction of the waves.apart along the direction of the waves.
S WAVESS WAVES
Second wave to reach seismographSecond wave to reach seismographTravels through solids onlyTravels through solids onlyCause rock particles to move at right Cause rock particles to move at right
angles to the direction the wave is angles to the direction the wave is travelingtraveling
L WAVESL WAVES
Slowest moving of the three wavesSlowest moving of the three wavesAlso called surface or long wavesAlso called surface or long wavesLast to be recorded by the seismographLast to be recorded by the seismographTravel over the earth’s surface similar to Travel over the earth’s surface similar to
ocean wavesocean wavesCause the greatest damageCause the greatest damage
SEISMOGRAPHSEISMOGRAPH
A device used to measure A device used to measure seismic wavesseismic waves
LOCATING THE EPICENTER
EARTHQUAKE SCALESEARTHQUAKE SCALES
RICHTER RICHTER
MERCALLIMERCALLI
RICHTER SCALERICHTER SCALE Scale that ranges from 1-10Scale that ranges from 1-10 Each whole number increases the Each whole number increases the
magnitude of the energy 31.7 timesmagnitude of the energy 31.7 times
Largest recorded magnitude - 9.5Largest recorded magnitude - 9.5 Above 7 - Major earthquakeAbove 7 - Major earthquake Between 6 and 7 - Moderate earthquakeBetween 6 and 7 - Moderate earthquake Between 2.5 and 6 - Minor earthquakeBetween 2.5 and 6 - Minor earthquake Less than 2.5 - MicroearthquakeLess than 2.5 - Microearthquake
MERCALLI SCALEMERCALLI SCALE
Measures the intensity of the damaged Measures the intensity of the damaged caused by the earthquakecaused by the earthquake
Scale of I - XII (1-12)Scale of I - XII (1-12)
I. Not felt except by a very fewI. Not felt except by a very few
II. Felt by a very few persons II. Felt by a very few persons onon
the upper floors of buildings the upper floors of buildings
III. Felt indoorsIII. Felt indoors
IV. Hanging objects swingIV. Hanging objects swing
V. Felt outdoorsV. Felt outdoors
VI. Felt by all, many scared andVI. Felt by all, many scared and run outdoors run outdoors
VII. Difficult to standVII. Difficult to stand
VIII. Damage slight in VIII. Damage slight in speciallyspecially
designed structures designed structures
IX. Damage considerable inIX. Damage considerable in specially designed specially designed
structuresstructures
X. Ground cracked, rail bentX. Ground cracked, rail bent
XI. Bridges destroyed, XI. Bridges destroyed, broad fissures in ground broad fissures in ground
XII. Damage totalXII. Damage total
Pacific Northwest Earthquake InformationREQUEST FOR EARTHQUAKE INFORM
ATION
EARTHQUAKE SAFETY
BEFORE - Be prepared BEFORE - Be prepared DURING - Stay calmDURING - Stay calmAFTER - Stay cautiousAFTER - Stay cautious
ASSIGNMENTWORKSHEET 6.3WORKSHEET 6.3Page 111, #1-5Page 111, #1-5