Transcript Earthquakes - Wikispaces

By: Colin Hetherington
What is an Earthquake?
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A series of vibrations induced in the earth's crust by the abrupt rupture and rebound of rocks in which elastic strain has been
slowly accumulating. (definition from http://dictionary.reference.com/browse/earthquake)
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Earthquakes are most often caused from the shearing within Transform Boundaries.
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The most common definition is: movement along a fault.
When the shearing between two plate tectonics erupt in an earthquake two different
seismic waves are sent out from the focus (or the point beneath Earth’s surface where
plate tectonics break under stress and shift).
• P-Waves = Primary Waves = fastest wave that travels through anything.
• S-Waves = Secondary Waves = slower wave that travels through
everything but liquid.
• Surface Waves = slowest waves that travel through buildings.
Additional Info.
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As already stated, S-Waves are unable to travel through
liquid resulting in what is referred to as a shadow zone
(where no S-Waves occur).
The seismic waves that most humans feel are the Surface
Waves which cause the collapsing of buildings and the
shaking of the ground.
Obviously earthquakes only occur in regions along
Fault/Boundary lines.
The reason for the sudden release in energy, is that when
the two large tectonic plates pass by each other, they do
not glide easily, but rather shear and get stick on rocks
until they suddenly break under the pressure. This is the
energy that creates the seismic waves.
Earthquake
Focus
Damage
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The damage caused by an earthquake entirely depends on where the seismic waves strike. For
example if an unpopulated region is struck by an earthquake, there will be minimal loss of life and
property. On the other hand, if a densely populated area is hit by an earthquake, the amount of life
and property damage will be very high.
Most commonly earthquakes destroy buildings, homes, bridges, telephone poles, dams and other
structures.
Not only are earthquakes themselves bad they often trigger a chain of disasters such as
landslides, tsunamis, floods, and aftershocks.
Scientists are sometimes able to predict large earthquakes from the small tremors on a fault line.
When caught in an earthquake stay clear of power lines, windows, and trees (falling materials)
and hold onto something sturdy.
Examples
The most recent (LARGE) earthquakes have occurred in …
• Japan
Haiti =
• Haiti
Chile =
• Chile
• New Zealand
• Phillipines
Philippines =
New Zealand =
Japan =
Historic Earthquakes
• The Largest earthquake in
history (our recorded history)
was in Chile on May 22, 1960
when 9.5 earthquake struck.
• But the most deadly
earthquake in recorded
history has occurred in
Shaanxi, China in 1556 when
830,000 people were killed
What are Tsunamis?
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Tsunamis are an unusually large sea wave produced by a seaquake or undersea
volcanic eruption (definition from http://dictionary.reference.com/browse/tsunami).
Tsunami waves are very fast traveling at around 600 mph (the speed of a jet plane)
therefore offering little time for coastlines to evacuate. For example if a Tsunamis was
generated on the far side of the Pacific Ocean, within 24 hours the waves would have
reached the California coastline.
Just like earthquakes, tsunamis most often occur near Transform Boundaries.
How Tsunamis Form
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Tsunamis most often are caused by very large earthquakes occurring near or under the ocean (in
other instances underwater volcanoes, land slides and very rarely meteorites cause tsunamis).
It is important to know that not all earthquakes generate tsunamis. (Must occur underneath water,
be large and create movements in the sea floor.
The process in which tsunamis are generated from earthquakes is much more complicated than
sudden push against a column of ocean water. An earthquakes magnitude and depth, water depth
in the area, the amount of vertical motion of the sea floor, the velocity of such motion, whether
there is slumping of sediments and the efficiency with which energy is transferred from the earth’s
crust to the ocean water are all factors in the generation of tsunamis.
Although when created these waves only reach to an average height of around 3 in. and above
(un-noticeable to a fisherman), as they get closer towards the shore/coast and the water becomes
shallower their waves become much larger at around 50-100 feet.
Damage
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As expected only areas near or on the shoreline can be effected from tsunamis.
As stated earlier, tsunamis can reach a height of 50-100 ft, this large increase in
height allows extensive flooding about 1000 ft or more into the coastline.
Obviously, the main type of damage caused by a tsunamis is large amounts of
flooding. Flooding to these extremes are so severe the ruin the land, buildings,
transportation and communication lines.
Unfortunately scientists still are unable to exactly predict tsunamis, but are able to
predict the most likely locations. (But a noticeable sign of a tsunami happens shortly
before the coastline is hit, when the water reseeds far beyond the low-tide line)
When caught in a tsunami, the best action is to quickly travel to high ground or to the
highest levels of buildings.
Examples of Tsunamis
• Some of the most current locations for
these disasters include:
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Japan
Solomon Islands
Thailand
Chile
Indonesia
Historic Tsunamis
• In our recorded history, the largest tsunami
happened in Lituya Bay, Alaska on July 9,
1958. This tsunami created a wave height
of 1720 ft.
• The most deadly tsunami
occurred in the Indian Ocean
on December 26, 2004 .
Killing over 230,000 people.
Current Disaster in Japan
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As most people are aware, on Friday, March 11, 2011 Japan was hit by a
9.0 earthquake which was followed by a large tsunami. The earthquake was
caused by transform boundaries near the Ring Of Fire. In fact, the
archipelago of Japan supposedly moved 8 feet to the east and the earth’s
axis moved about 4 in., due to the massive earthquake. Although the
earthquake was enormous, the most deaths are coming from the
devastating tsunami which has 21,459 confirmed deaths and over 20,000
missing. Its obvious that this is a very serious and drastic event as the
problems keep coming from Japan. With the high levels of radiation coming
from the leaking Nuclear Reactors and the damage cost reaching over 230
billion dollars.
To donate go to:
https://american.redc
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Videos of Tsunamis
• http://www.youtube.com/watch?v=TRDpTEjumdo
• http://www.youtube.com/watch?v=w9ygYqj4rVM
Videos of Earthquakes
• http://www.youtube.com/watch?v=1CFwY0ued0I
• http://www.youtube.com/watch?v=CcFVxl8oclY
Fun Activities
• http://tlc.discovery.com/convergence/quakes/interactives/
makeaquake.html
• http://www.edumedia-sciences.com/en/a98tsunami#textual
• http://www.stopdisastersgame.org/en/playgame.html
Website Sources
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http://earthscience-longoria.blogspot.com/2009/04/how-and-where-earthquakes-occur.html
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http://goiloilo.com/wp-content/uploads/2010/01/Haiti-Earthquake.JPG
http://www.beersteak.com/wp-content/uploads/2010/01/2010-haiti-earthquake.jpg
http://resources3.news.com.au/images/2011/02/24/1226011/183279-nz-earthquake.jpg
http://science.nationalgeographic.com/staticfiles/NGS/Shared/StaticFiles/Science/Images/Content
/earthquake-next-one-photo-rtre2o5-sw.jpg
http://static.howstuffworks.com/gif/tsunami-formation.gif
http://www.richmond.ca/__shared/assets/Tsunami_-_Fig12408.jpg
http://www.aheartforhaiti.com/images/Haiti-Earthquake-2010%287%29.jpg
http://www.doi.gov/emergency/images/Rev_Am_Sam_Pago_Pago1.jpg
http://www.abc.net.au/reslib/200903/r354220_1627020.jpg
http://www.celsias.com/media/uploads/admin/Tsunami_damage1.JPG
http://www.sciencemediacentre.co.nz/wp-content/upload/2010/12/earthquake-gallery-3.jpg
http://en.wikipedia.org/wiki/2004_Indian_Ocean_earthquake_and_tsunami
http://qmackie.files.wordpress.com/2010/02/lituya-from-panoramio.jpg?w=500&h=521
http://www.whatsonxiamen.com/news_images/505522.jpg
http://photos.upi.com/slideshow/lbox/28a2a62a7499abb8a957328e0867f9a9/88-magnitudeearthquake.jpg
http://library.thinkquest.org/04oct/01356/images/wave_model.jpg
http://www.calstatela.edu/dept/geology/GEOL351Images/TsunamiHotelDamage(2).jpg
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