Upload
davedelg1
View
8.021
Download
4
Tags:
Embed Size (px)
DESCRIPTION
Citation preview
EarthquakesEarthquakesare the vibrationsvibrations caused by sudden
movements of Earth’s rocks.
Forces within the crust cause rocks to
bend or break.
Where do most Earthquakes occur?
12%
88% Ring of Fire
All Others
Most Earthquakes occur:
*along the “Ring of Fire”, a belt which circles the Pacific Ocean
*88% of all earthquakes occur here
Earthquake Belts
along the belts which run through» central Asia» mid-ocean ridges» Mediterranean Sea» Caribbean Sea
Each black dot represents one earthquake over a 10 year period
Earthquake Belts
*due to one or a combination of more than one of three kinds of forces:
1. tension 2. compression 3. shearing
Elastic Rebound
ForcesForces may causerock to:
1. * Fracture » breaks in rock
where no movement has occurred
ForcesForces may causerock to:
2. * Fault » fractures in rock where
movement has occurred» may occur in any direction
along the surface of the break (fault plane)
*Fault Types
»may be one of three types:
1. normal
2. reverse
3. strike-slip (transform)
Normal Fault
Normal Fault
Normal Fault
Normal Fault Structures
Reverse Fault
Reverse Fault
Reverse Fault
Reverse Fault Structures
Strike-slip (Transform) Fault
Strike-slip (Transform) Fault
Strike-Slip Fault
Strike Slip Fault
ForcesForces may cause rock to:
3. *Fold » due to compression» may form one single bend (monocline)» or may form alternating ridges (anticlines)
and troughs (synclines)
monocline
anticlines
synclines
Folded Rocks
anticline
syncline
Where are the oldest rocks exposed at the surface?
Folded Rocks
monocline
rock has a gently dipping bend in the horizontal rock layer.
Seismic Waves
originate from the *focus, the actual point on the fault where movement occurs
affect the point on the earth surface directly above the focus, called the *epicenter
Seismic Waves
may be a *body wave:
1. *P- wave (primary) - rocks particles back and forth, fastest wave, first to arrive
2. *S - wave (secondary) - rocks move forward but vibrate at right angles to the direction of movement, slower than p - wave, arrives later
Seismic Waves
may be a *surface wave:
3. *L- wave (longitudinal) - vibrates the earth’s crust like an ocean wave
is the most destructive
travels very slow compared to P & S – waves
last to reach the seismic station
Seismic Waves
Earthquake DestructionDestruction
Intensityis a measure of the physical damage or geologic change
measured by the
Mercalli Scale
Magnitudeis a measure of the strength of an earthquake recorded by seismographs
measured by the
Richter Scale
How Seismographs Work
Seismograph
Richter Scale
For every increase in 1 on the Richter
Scale….
there is an increase of 32 times the
energy released!
Seismogram
P and S Wave Travel Time Curves
Use the difference in P and S wave arrival times to calculate the distance from the epicenter.
Locating Earthquakes
Station 1Station 1
Locating Earthquakes
Station 2
Locating Earthquakes
Station 3
Locating Earthquakes - Depth
Seismic Waves in the Earth
Seismic Waves in the Earth
Earth’s Interior
P & S waves slow when they hit the upper mantle (asthenosphere)
speed up again when they hit the solid lower mantle
P waves are slowed and deflected when they hit the liquid outer core
Earth’s Interior
S waves do not travel through the liquid outer core
Shadow Zone results between 105o and 140o from an earthquake’s focus
Earth’s Interior
Earth’s Interior
Why is the inner core a solid?
Earth’s Interior
Crust: 3 – 60 miles thick, hard, brittle, continents are thicker than ocean
Mantle: thickest layer, denser than crust, upper mantle is plastic-like (flows under pressure)» Separated from the crust by the Moho or
Mohorovicic Discontinuity» Made of silicon, oxygen, magnesium, iron
Earth’s Interior
Core: innermost layer, made of iron and nickel
» Inner core is solid
» Outer core is liquid
Earthquake Damage
Earthquake Damage
Earthquake Damage
Earthquake Damage
Earthquake Damage
Earthquake Damage
Earthquake Damage
Earthquake Damage
Earthquake Damage
Earthquake Damage
Earthquake Damage
Earthquake Safety
Outdoors – move to an open area» Stay away from chimneys, buildings, trees» Stay away from beaches
Indoors » move away from windows, large objects» Seek shelter under table, desk, doorway, basement stairs» Turn off electricity, water, gas if possible
Tsunamis
Probably Caused by Submarine Landslides
Travel about 400 m.p.h.
Pass Unnoticed at Sea, Cause Damage on Shore
Tsunamis
Whether or Not Damage Occurs Depends on: » Direction of Travel » Harbor Shape » Bottom topography» Tide & Weather
Tsunamis
Satellite images from NASA show the destruction caused by a tsunami to the Indonesian province of Aceh. The left photo shows the town of Lhoknga before the tsunami hit on Dec. 24, 2004.
Tsunamis
Tsunamis
Tsunamis