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The official death toll to about 2,800 but the Miyagi police chief
has said that more than 10,000 people are estimated to have died
in his province alone.
http://www.bbc.co.uk/news/world-asia-pacific-12729485
http://www.youtube.com/watch?v=TRDpTEjumdo
http://www.youtube.com/watch?v=AZ5WPXxNzPU
Earth’s Interiors
How we know what’s inside
•Astronomy
•Drilling through the crust
•Earth’s delivery service
-Kimberlite Pipes and Xenoliths
-Ophiolites
•Seismic data
-Vibrational energy waves
- Earthquake data
Astronomy
Calculating Earth’s Density
- Gravitational influence, mass
- Volume, Shape, Diameter
- calc. Density of Earth 5.5 g/cm3
- Surface 2.8 g/cm3
Drilling through the crust
Describing core. From left to right: Daniele Brunelli (Igneous Petrologist, Centre National de la
Recherché Scientifique), Eric Hellebrand (Igneous Petrologist, Max-Planck-Institüt für Chemie),
Hiro Tamura Hasebe (Igneous Petrologist, Kanazawa University), Heidi-Elisabeth Hansen
(Igneous Petrologist, University of Bergen), Kevin Johnson (Igneous Petrologist, University of
Hawaii), Satoko Ishimaru (Igneous Petrologist, Kanazawa University), Natsue Abe (Igneous
Petrologist, Japan Marine Science and Technology Center), and Xixi Zhao (Paleomagnetist,
University of California, Santa Cruz) in the background. [Photo ID: exp305_006]
Drilling through the crust
Earth’s delivery service
Kimberlite
pipe
Xenolith
Kimberlite Mine in South Africa
Seismic Data
What causes earthquakes
- Elastic rebound theory
Seismographs
Instrument for measuring magnitude of earthquakes
Seismographs
Types of Siesmic Waves
Body Waves - travel thru the Earth
- P waves
- S waves
Surface Waves - travel around the Earth
- Love waves
- Rayleigh waves, ground roll
P Wave- result from alternating
compression and expansion of material
P waves:
- primary waves
- compressional wave
- movement is in the same direction
that the wave is traveling
- highest velocity seismic wave (4mi/s)
- travel through solids, liquids, and
gases
Earthquake Waves
S wave - distortion of material, perpendicular
to the direction the wave is traveling.
S waves:
- secondary waves
- transverse or shear waves
- slower than P waves (2mi/s)
- can only pass through solids
- slightly greater amplitude than P waves
Earthquake Waves
Rayleigh
Surface Waves
Love
Surface Wave:
- a seismic wave that travels along the
surface of the Earth Surface Waves:
- dampen quickly, don't travel very far
Earthquake Equivalent
Amplitude tons of TNT
Richter Scale
0
0.6
1
20
2
600
3
20 000
Most people near epicenter feel the quake.
4
60 000
A small fission atomic bomb. Quakes above 4.5 can cause local damage
5
20 000 000
A standard fission bomb, similar to the first bomb tested in New Mexico, U.S.
6
60 000 000
A hydrogen bomb; can cause great damage locally.
7
20 billion
Enough energy to heat New York City for 1 year
Smallest quake people can normally feel
Large enough to be detected all over globe
8
60 billion
Largest known: 8.9 in Japan and in Chile/Ecuador
San Francisco destroyed by 8.25 in 1906
9
20 trillion
Roughly the world's energy usage in a year
Modified Mercalli Intensity Scale
from FEMA
I. People do not feel any Earth movement.
II. A few people might notice movement if they are at rest and/or on the
upper floors of tall buildings.
III. Many people indoors feel movement. Hanging objects swing back and
forth. People outdoors might not realize that an earthquake is occurring.
IV. Most people indoors feel movement. Hanging objects swing. Dishes,
windows, and doors rattle. The earthquake feels like a heavy truck hitting
the walls. A few people outdoors may feel movement. Parked cars rock.
V. Almost everyone feels movement. Sleeping people are awakened.
Doors swing open or close. Dishes are broken. Pictures on the wall move.
Small objects move or are turned over. Trees might shake. Liquids might
spill out of open containers.
VI. Everyone feels movement. People have trouble walking. Objects fall
from shelves. Pictures fall off walls. Furniture moves. Plaster in walls
might crack. Trees and bushes shake. Damage is slight in poorly built
buildings. No structural damage.
VII. People have difficulty standing. Drivers feel their cars shaking. Some
furniture breaks. Loose bricks fall from buildings. Damage is slight to
moderate in well-built buildings; considerable in poorly built buildings.
VIII. Drivers have trouble steering. Houses that are not bolted down might
shift on their foundations. Tall structures such as towers and chimneys
might twist and fall. Well-built buildings suffer slight damage. Poorly built
structures suffer severe damage. Tree branches break. Hillsides might
crack if the ground is wet. Water levels in wells might change.
IX. Well-built buildings suffer considerable damage. Houses that are not
bolted down move off their foundations. Some underground pipes are
broken. The ground cracks. Reservoirs suffer serious damage.
X. Most buildings and their foundations are destroyed. Some bridges are
destroyed. Dams are seriously damaged. Large landslides occur. Water is
thrown on the banks of canals, rivers, lakes. The ground cracks in large
areas. Railroad tracks are bent slightly.
XI. Most buildings collapse. Some bridges are destroyed. Large cracks
appear in the ground. Underground pipelines are destroyed. Railroad
tracks are badly bent.
XII. Almost everything is destroyed. Objects are thrown into the air. The
ground moves in waves or ripples. Large amounts of rock may move.
Liquefaction
Liquefaction
A phenomenon in which the strength and
stiffness of a soil is reduced by earthquake
shaking.
Niigata, Japan 1964
Sand boil
1989 Loma Prieta
Liquefaction
induced road
failure
Tsunami
Travel of Seismic Waves
In homogeneous material, they
travel in a straight line.
When seismic waves encounter a
boundary, they will reflect or refract.
Homogeneous
Heterogeneous
Reflection – return of wave off a
boundary (bounce back)
Refraction – change in direction
and velocity of the wave
Bedrock vs. Unconsolidated Sediments
We hypothesize that the outer core is molten
because S waves will not pass through it.
Seismic
Shadow
Zones
S-Wave
Shadow Zone
P-Wave
Shadow Zone
P-Wave Shadow Zone
Seismic Discontinuities
We hypothesize that the asthenosphere is
partially molten because seismic waves
slow down when they enter it.
Earth’s Layers
How do we know exactly where
an earthquake occurs?
Benioff Zone
Associated with Subduction
Cocos
Plate
Subducting
Under the
North
American
Plate
Current Seismic Activity
http://earthquake.usgs.gov/