earthquakes. epicenter focus fault fault scarp the focus is the point where the earthquake starts...
TRANSCRIPT
Earthquakes
Earthquakes
Epicenter
Focus
Fault
Fault Scarp
• The focus is the point where the earthquake starts UNDER the surface of the earth.
• The epicenter is the point directly above the focus on the surface of the earth.
• The fault is the BREAK in the crust where the earthquake occurs.
The Elastic Rebound hypothesis states that when rocks (earth’s crust) is deformed, they break, releasing energy that results in the trembling of earthquakes
Earthquakes can occur along transform, convergentAND divergent boundaries!
• _Foreshocks__ are vibrations or small earthquakes that are seen before the major earthquake
• Aftershocks_ are vibrations or small earthquakes that are felt after an earthquake
What is an earthquake?• An earthquake is the shaking of the ground due
to the movements of tectonic plates.• Earthquakes can occur along convergent,
transform and divergent boundaries.
What Causes Earthquakes?• As tectonic plates
push, pull or scrape against each other, stress builds up along faults until the rocks finally move
• A fault is a break in the Earth’s crust where plates slide, push or pull against each other
The focus of an earthquake is the point INSIDE the Earth where the earthquake starts. It is the place below the earth’s surface where the rocks tear, come apart, or collide.
The epicenter is the location on the surface of the Earth directly above the focus. Surface waves move outward from the epicenter.
The fault is the break in the
crust where the earthquake occurs,
between two blocks of rock that
have moved past each other.
Parts of an Earthquake
P WAVESP waves (primary waves) are also known as
compression waves.
Movement: They push and pull in the direction that the wave is traveling.
Speed: They arrive first
Destruction: cause the least damage. (speed and destruction)
http://www.geo.mtu.edu/UPSeis/images/P-wave_animation.gif
S WAVESMovement:S waves (secondary waves)
move in right angles
Speed: S waves are slower than P waves. They arrive second (hence the name).
Destruction: cause a moderate amount of damage.
http://www.geo.mtu.edu/UPSeis/images/S-wave_animation.gif
SURFACE WAVES• Travel along the earth’s surface. They do
not travel through the Earth. • Movement: They move up and down or
side to side.
Speed: It is the slowest
Destruction: this is the most destructive type of wave!
LETS SEE THIS IN ACTION!
NAME
THATWAVE
NAME THAT WAVE!
1)I am the type of wave that does not travel through the earth.
P Wave, S Wave, or Surface Wave
NAME THAT WAVE!
2)
NAME THAT WAVE!
3) I am short for “secondary wave.”
NAME THAT WAVE!
4)
NAME THAT WAVE!
5) I arrive last at the seismograph station.
NAME THAT WAVE!
6)
NAME THAT WAVE!
7) I am the most destructive type of wave.
NAME THAT WAVE!
8)
NAME THAT WAVE!
9) I am the type of wave that arrives at a seismograph first.
WHAT THIS LOOKS LIKE IN REAL LIFE
Let’s label the boxes as a class. Then draw them on your notes!
When an earthquake happens, scientists want to know where it happens.
Scientists need to find the epicenter. Scientists need to find the source.
Epicenter = Difference in __________________
-
HOW SCIENTISTS USE THIS
SCENARIO 1: Watch!
Answer 1 ____________________SCENARIO 2: A P Wave arrives at the seismograph station 3 minutes after an earthquake. An S Wave arrives 8 minutes after an earthquake. What is the difference in arrival time?
Answer 2 ___________________
SCENARIO 3: At 10:32 a P Wave arrives. At 10:45 and S Wave arrives. What is the difference in arrival time?
Answer 3 _______________________
SCENARIO 1: Watch!
P Wave = _____________________
S Wave = _____________________
Answer = ______________________
SCENARIO 2:
P Wave = _____________________
S Wave = _____________________
Answer = ______________________
9 10 11 12 13 14 15 16 17 18 19 20 3:00 3:02 3:04 3:06 3:08 3:10 3:12 3:14 3:16
1. What is the elastic rebound hypothesis?2. Around which boundaries can earthquakes occur?3. Identify the fault, epicenter, and focus in the picture right. A =? B = ? C =?4. What happens when lithosphere undergoes subduction into the mantle?
A
C
B
Warm Up Friday, 10/18/13
1. Determine the difference in the travel-times between the first P wave and the first S wave, if the seismic station is 1000 kilometers from the epicenter.
2. Determine the difference in the travel-times between the first P wave and the first S wave, if the seismic station is 500 miles from the epicenter.
3. Determine the difference in the travel-times between the first P wave and the first S wave, if the seismic station is 1,700 miles from the epicenter.
According to Figure 8-1, what is the distance between the seismic station and an earthquake epicenter, if the first S wave arrives 6.5 minutes after the first P wave?
2. According to Figure 8-1, what is the distance between the seismic station and an earthquake epicenter, if the first S wave arrives 2.0 minutes after the first P wave?
3. According to Figure 8-1, what is the distance between the seismic station and an earthquake epicenter, if the first S wave arrives 4.0 minutes after the first P wave?
4. According to Figure 8-1, what is the distance between the seismic station and an earthquake epicenter, if the first S wave arrives 5 minutes and 40 s after the first P wave?
5. According to Figure 8-1, what is the distance between the seismic station and an earthquake epicenter, if the first S wave arrives 3.0 minutes after the first P wave?
6. According to Figure 8-1, what is the distance between the seismic station and an earthquake epicenter, if the first S wave arrives 4 minutes and 30 seconds after the first P wave?
Consequences of earthquakes
https://www.youtube.com/watch?v=jBdvvXyS-r4
Earthquakes...HOLD ON!
Video: How to survive an Earthquake
How often do Earthquakes strike?http://earthquake.usgs.gov/earthquakes/
What about in Charlotte?http://earthquake.usgs.gov/earthquakes/states/north_carolina/hazards.php
Earthquakes...HOLD ON!
-Earthquakes can cause landslides, avalanches, fires and tsunamis.-Damage from earthquakes includes fallen objects, crumbled foundations, liquefaction of the lithosphere, power outages, and fires.
TsunamisHuge wavelength (crest to crest)• A tsunami triggered by an earthquake occurs where a slab of the __sea_______ floor is displaced __vertically__along a fault.It can also occur when the vibration of a quake sets __an underwater landslide___in motion.
Tsunamis
Earthquakes...HOLD ON!
-To prevent damage of earthquakes, we need to increase the flexibility of buildings.-More damage is done based on the type of ground and structure is built upon.-By diversifying the height and shape of buildings, we can minimize damage done to a region by an earthquake.
http://www.youtube.com/watch?v=K1qY8nPqcCw
Landslides
Landslides
• With many earthquakes, the greatest damage to structures is from _landslides and ground subsidence__or the sinking of the ground triggered by _vibrations__Liquefaction occurs when soil loses its strength and behaves like a __liquid_______, causing __large sections of the ground to collapse, liquefy or subside__
What type of destruction occurs from Earthquakes?
What type of destruction occurs from Earthquakes?
• The greatest destruction is often caused by fires when _gas and electric lines _are cut and __water lines_are also broken, so the fire can’t be stopped.More than _100,000__people died in fires from a 1923 earthquake in Japan.
What type of destruction occurs from Earthquakes?
• An avalanche is a sudden fall of _ice_ and ___snow__.In 1970, a severe earthquake of the coast of _Peru_____ caused a disastrous slide of snow and rock that killed __18,000___ people in the valley below.
Seismic intensity is affected by rock type.
Amplitude of oscillation
Form a hypothesis about how would you expect the houses to react during an EQ.
Seismic intensity is affected by rock type.
Amplitude of oscillation
Form a hypothesis about how would you expect the houses to react during an EQ.
Seismic intensity is affected by rock type.
Amplitude of oscillation increasing
Solid bedrock is the best rock to build upon. As the rock becomes
softer, the damage done by earthquakes increases.
Earthquake-Proof Buildings:• More flexible wood-framed
homes or steel-framed buildings are less damaged
• Use Light-weight building materials
• Bolted or welded connections that can withstand loads well above the design load
• Flexible beams in the building frame
• Floors securely fastened to the frames
What needs to be considered when constructing an earthquake-proof building?
• Distribution of weight• Variation in shape• Variation in height• Variation in foundation material
San Francisco's TransAmerica pyramid is famous for its architecture. Diagonal trusses at its base protect it from both horizontal and vertical forces.
An exemplary Model• The Hagia Sophia in Istanbul, Turkey has survived
all magnitudes of earthquakes for nearly 1,500 years.