Transcript Earthquakes Geohazards Notesx

Seismic Waves and Scales
 Natural vibrations of ground caused by
movement along fractures in Earth’s crust.
 Earthquakes can cause major damage.
EQ Destruction
 Earthquakes correlate with plate boundaries.
http://www.earthquakeusgs.org/wp-content/uploads/Map-of-major-earthquakes-in-the-world-1.jpg
• Rocks fail when stress
is applied too quickly
or is too great.
• Faults are also likely
places for earthquakes
to occur.
• Resulting fracture(s) in
the Earth’s crust along
which movement
occurs is called a fault.
San Andreas fault zone, Carrizo Plains, central
California. Photo by R.E. Wallace, USGS
Focus - point where
earthquakes
originates. Usually
several km below
the surface
Epicenter - point on
the Earth’s surface
directly above the
focus of an
earthquake
Which is usually more dangerous,
a shallow focus EQ or a deep focus EQ?
 Normal fault
 Bodies of rock are pulled from opposite sides.
http://windupradio.com/earthquakes/causes.htm
 Reverse fault
 When horizontal stress is exerted on a body
from opposite sides.
http://windupradio.com/earthquakes/causes.htm
 Strike-slip fault
 Movement is horizontally past each other.
http://windupradio.com/earthquakes/causes.htm
http://structuralgeo.files.wordpress.com/2013/07/reverse-fault-zone-ketobe-knob-utah.jpeg
http://geology.uprm.edu/Morelock/1_image/fltoffst.jpg
http://www001.upp.so-net.ne.jp/fl-fg/04_fault/04-01_normal_fault-jyougashima-810X540-060730DSC_0920.jpg
 Vibrations are called seismic waves.
 There are 3 types of seismic waves:
 Primary waves
 Secondary waves
 Surface waves
 PRIMARY or P-WAVES - squeeze and pull
rocks in the same direction; can travel
through solids and liquids
 SECONDARY or S-WAVES - rocks move
at right angles; an up and down wave;
can only travel through solids
 SURFACE WAVES - move in 2 directions; up and
down and side to side; occur on surface of earth.
Most of the knowledge of the Earth’s interior comes
from the study of seismic waves, which change speed
and direction when they encounter different materials
 Can P and S waves from an earthquake be
detected everywhere on Earth?
Remember:
• P waves travel
through solids and
liquids
• S waves travel only
solids
Seismic Waves
 Richter Scale - used to describe the
magnitude or energy released from an
earthquake.
 Based on size of largest seismic wave
generated by earthquake.
 Based on powers of 10, so a 9.0 EQ is 10 X
more powerful than an 8.0 EQ!
 Modified Mercalli Scale - used to describe the
intensity or damage from an earthquake.
http://cdn.sheknows.com/articles/crave/seismograph-machine.jpg
 The difference in
arrival times
between the P wave
and S wave (S-P
Interval) can be used
to determine the
distance between
the earthquake’s
epicenter and the
seismograph station.
Seismic Station: Raleigh, NC
http://ohhs.ohsd.net/~brick/ear/earr_eq_ampl.htm
What is the S-P Interval
from this seismogram?
37 seconds
How far is the seismic
station in Raleigh
from the earthquake?
360 kilometers
http://ohhs.ohsd.net/~brick/ear/earr_eq_ampl.htm
Raleigh, NC = 360 km
http://www.yellowmaps.com/maps/img/US/blank-base/mjrcity.jpg
Raleigh, NC = 360 km
Nashville, TN = 825 km
http://www.yellowmaps.com/maps/img/US/blank-base/mjrcity.jpg
Raleigh, NC = 360 km
Nashville, TN = 825 km
Buffalo, NY = 1200 km
Where was the earthquake’s epicenter?
http://www.yellowmaps.com/maps/img/US/blank-base/mjrcity.jpg
http://www.npenn.org/page/5063
Even with all the monitoring that occurs, earthquakes cannot be predicted.
The variables involved are too involved and dynamic to find a correlation in
data gathered to say without doubt when they will occur. The risk in the
United States is varied and can be seen on this map.
http://www.npenn.org/page/5063
Valdevia Chile, 1960 - Magnitude 9.5
1,655 people were killed.
The quake triggered a tsunami that killed 61 people in Hawaii, 138 in Japan and 32 in the
Philippines.
The earthquake ruptured where the Nazca Plate dives underneath the South American
Plate, on the Peru-Chile Trench.
Tsunami -Large waves generated by an
earthquake that occurs in the ocean
This photograph of the tsunami arriving on shore in Japan
shows the vertical height of the wave. Note the crest which is
a tree top level. That would make the height of the wave
roughly 30 feet.
http://www.nytimes.com/interactive/2011/03/13/world/asia/satellitephotos-japan-before-and-after-tsunami.html
Warm Up:
What is a geohazard? List as many
geohazards as you can.
 Definition: A harmful event caused by the earth
 Examples:
1. Volcanoes
2. Lahar (mud) flows
3. Earthquakes
4. Tsunamis
5. Landslides
6. Avalanches
7. Sinkholes
8. Flooding
Where are you most
likely to experience
one?
http://www.earthquakeusgs.org/wp-content/uploads/Map-of-major-earthquakes-in-the-world-1.jpg
 Definition: A harmful event caused by the earth
 Examples:
1. Volcanoes
2. Lahar (mud) flows
3. Earthquakes
4. Tsunamis
5. Landslides
6. Avalanches
7. Sinkholes
8. Flooding
Which is the most
dangerous?
Which one are you most
likely to die from?
 Chances of dying from
being struck by lightning?
 In in 2,320,000
http://www.accuweather.com/en/weather-news/does-lightning-strike-men-or-w/51439
 Chances of being attacked
and killed by a shark?
 1 in 3,748,067
http://aquaviews.net/explore-the-blue/5-shark-attack/
 Definition: A harmful event caused by the earth
 Examples:
1. Volcanoes
2. Lahar (mud) flows
3. Earthquakes
4. Tsunamis
5. Landslides
6. Avalanches
7. Sinkholes
8. Flooding
Chances of Dying:
1 in 80,000
?
1 in 131, 890
1 in 500,000
?
1 in 9,300,000
?
1 in 30,000
 Definition: A harmful event caused by the earth
 Examples:
1. Volcanoes
2. Lahar (mud) flows
3. Earthquakes
4. Tsunamis
5. Landslides
6. Avalanches
7. Sinkholes
8. Flooding
Assignment:
Create a Public Service
Announcement in the form of a
illustrated and descriptive poster,
including the following components…
• Description (What is it?)
• Causes (Why does it happen?)
• Preparations (How can we as a
society and you as an individual be
prepared for one?)
• Survival (How can you survive
one?)