EARTHQUAKES ANDPLATE TECTONICS
CHAPTER 6 SECTION 1CHAPTER 6 SECTION 1
ELASTIC REBOUNDTHEORYELASTIC REBOUNDTHEORY
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 inthe form of vibrations called seismicwaves.Original earthquake releases energy inthe form of vibrations called seismicwaves.
These vibrations may increase stress inother rocks along the fault.These vibrations may increase stress inother rocks along the fault.
The increased stress on these rocks maycause them to fracture and spring back.The increased stress on these rocks maycause them to fracture and spring back.
The series of smaller tremors are calledaftershocks.The series of smaller tremors are calledaftershocks.
FOCUSFOCUS
Area along a fault where the slippage firstoccursArea along a fault where the slippage firstoccurs
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 OFEARTHQUAKES INWASHINGTON 1977-1996FOCUS DEPTH OFEARTHQUAKES INWASHINGTON 1977-1996
EPICENTEREPICENTER
A point on the earth’ssurface directly above thefocusA point on the earth’ssurface directly above thefocus
MAJOR EARTHQUAKE ZONESMAJOR EARTHQUAKE ZONES
Pacific Ring of FirePacific Ring of Fire
Mid-ocean ridgesMid-ocean ridges
Eurasian-Melanesian Mountain BeltEurasian-Melanesian Mountain Belt
MAJOR EARTHQUAKESAREASMAJOR EARTHQUAKESAREAS
PUGET SOUND FAULTZONESPUGET SOUND FAULTZONES
MagnitudeMagnitude
STRUCTURAL DAMAGEKobe EarthquakeSTRUCTURAL DAMAGEKobe Earthquake
LIQUEFACTIONKobeLIQUEFACTIONKobe
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 wave
First recorded on seismographFirst recorded on seismograph
Travel through solid and liquidTravel through solid and liquid
Cause rock particles to move together andapart along the direction of the waves.Cause rock particles to move together andapart along the direction of the waves.
S WAVESS WAVES
Second wave to reach seismographSecond wave to reach seismograph
Travels through solids onlyTravels through solids only
Cause rock particles to move at rightangles to the direction the wave istravelingCause rock particles to move at rightangles to the direction the wave istraveling
L WAVESL WAVES
Slowest moving of the three wavesSlowest moving of the three waves
Also called surface or long wavesAlso called surface or long waves
Last to be recorded by the seismographLast to be recorded by the seismograph
Travel over the earth’s surface similar toocean wavesTravel over the earth’s surface similar toocean waves
Cause the greatest damageCause the greatest damage
SEISMOGRAPH A device used to measureseismic wavesSEISMOGRAPH A device used to measureseismic waves
LOCATING THEEPICENTER
EARTHQUAKE SCALESEARTHQUAKE SCALES
RICHTERRICHTER
MERCALLIMERCALLI
RICHTER SCALERICHTER SCALE
Scale that ranges from 1-10Scale that ranges from 1-10
Each whole number increases themagnitude of the energy 31.7 timesEach whole number increases themagnitude 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 - ModerateearthquakeBetween 6 and 7 - Moderateearthquake
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 damagedcaused by the earthquakeMeasures the intensity of the damagedcaused 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 personson the upper floors of buildingsII. Felt by a very few personson 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 and run outdoorsVI. Felt by all, many scared and run outdoors
VII. Difficult to standVII. Difficult to stand
VIII. Damage slight inspecially designed structuresVIII. Damage slight inspecially designed structures
IX. Damage considerable in specially designedstructuresIX. Damage considerable in specially designedstructures
X. Ground cracked, rail bentX. Ground cracked, rail bent
XI. Bridges destroyed, broad fissures in groundXI. Bridges destroyed, broad fissures in ground
XII. Damage totalXII. Damage total
EARTHQUAKE SAFETY
§BEFORE - Be prepared§BEFORE - Be prepared
§DURING - Stay calm§DURING - Stay calm
§AFTER - Stay cautious§AFTER - Stay cautious
ASSIGNMENT
§WORKSHEET 6.3§WORKSHEET 6.3
§Page 111, #1-5§Page 111, #1-5