1. Earthquakes

2. Earthquakes
Fault Scarp
Epicenter
Focus
Fault

3. 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.

4. 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, convergent
AND divergent boundaries!

6. _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

7. 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.

8. 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

9. Parts of an Earthquake
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.

10. P WAVES P 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)

12. S WAVES Movement: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.

14. 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!

15. LETS SEE THIS IN ACTION!

16. NAME
THAT
WAVE

17. NAME THAT WAVE!
I am the type of wave that does not travel through the earth.
P Wave, S Wave, or Surface Wave

18. NAME THAT WAVE! 2)

19. NAME THAT WAVE!
3) I am short for “secondary wave.”

20. NAME THAT WAVE! 4)

21. NAME THAT WAVE!
5) I arrive last at the seismograph station.

22. NAME THAT WAVE! 6)

23. NAME THAT WAVE!
7) I am the most destructive type of wave.

24. NAME THAT WAVE! 8)

25. 9) I am the type of wave that arrives at a seismograph first.
NAME THAT WAVE!
9) I am the type of wave that arrives at a seismograph first.

26. WHAT THIS LOOKS LIKE IN REAL LIFE
Let’s label the boxes as a class.
Then draw them on your notes!

27. Epicenter = Difference in __________________ -
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 __________________ -

28. 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 _______________________

29. P Wave = _____________________ S Wave = _____________________
3:00 3:02 3:04 3: :08 3:10 3:12 3:14 3:16
SCENARIO 1: Watch!
P Wave = _____________________
S Wave = _____________________
Answer = ______________________
SCENARIO 2:
P Wave = _____________________
S Wave = _____________________
Answer = ______________________

30. What is the elastic rebound hypothesis?
Warm Up Friday, 10/18/13
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? B A C

31. 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.

32. 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.

33. 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.

34. 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?

35. 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?

36. 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?

37. 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?

38. 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?

39. 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?

40. Consequences of earthquakes

41. Earthquakes...HOLD ON! Video: How to survive an Earthquake
How often do Earthquakes strike?
What about in Charlotte?

42. 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.

43. Huge wavelength (crest to crest)
Tsunamis
Huge 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.

44. Tsunamis

45. 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.

46. Landslides

47. 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__

48. What type of destruction occurs from Earthquakes?

49. 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.

50. 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.

51. Seismic intensity is affected by rock type.
A major influence on earthquake damage is the ground that buildings are built upon. In the San Francisco Bay area, soft muddy areas experience much large ground oscillations than do areas of hard bedrock. Earthquake damage tends to be high in Bay Mud areas and lower in areas underlain by bedrock.
The level of shaking is controlled by the proximity of the earthquake source to the affected region and the types of rocks that seismic waves pass through en route (particularly those at or near the ground surface).
Generally, the bigger and closer the earthquake, the stronger the shaking. But there have been large earthquakes with very little damage either because they caused little shaking or because the buildings were built to withstand that kind of shaking. In other cases, moderate earthquakes have caused significant damage either because the shaking was locally amplified, or more likely because the structures were poorly engineered.
Amplitude of oscillation
Form a hypothesis about how would you expect the houses to react during an EQ.

52. Seismic intensity is affected by rock type.
A major influence on earthquake damage is the ground that buildings are built upon. In the San Francisco Bay area, soft muddy areas experience much large ground oscillations than do areas of hard bedrock. Earthquake damage tends to be high in Bay Mud areas and lower in areas underlain by bedrock.
The level of shaking is controlled by the proximity of the earthquake source to the affected region and the types of rocks that seismic waves pass through en route (particularly those at or near the ground surface).
Generally, the bigger and closer the earthquake, the stronger the shaking. But there have been large earthquakes with very little damage either because they caused little shaking or because the buildings were built to withstand that kind of shaking. In other cases, moderate earthquakes have caused significant damage either because the shaking was locally amplified, or more likely because the structures were poorly engineered.
Amplitude of oscillation
Form a hypothesis about how would you expect the houses to react during an EQ.

53. Seismic intensity is affected by rock type.
This drawing does not show the S and P-wave arrivals on the seismogram. Rather, it shows how the seismic wave oscillates as it enters different materials.
The least damage occurs where buildings are constructed on bedrock. Note that the seismogram signal through “solid bedrock” is a high-frequency, low-amplitude.
By the time the seismic wave reaches the “well-consolidated sediment” it begins to wobble with more amplitude but less frequently.
The “poorly consolidated” sediment is even worse.
As the wave enters the “water-saturated sand and mud” the wave records a low-frequency, high-amplitude signal. It really gets rolling and can cause liquifaction [during ground shaking, some sandy, water-saturated soils can behave like liquids rather than solids. See the activity in the Exploratorium website noted below.]
Background below from
During a quake, the squeezing done by the seismic waves happens very quickly, and the water doesn’t have time to flow out of the way of the sand particles. So as the particles try to move into a denser configuration, they push on the water, causing an increase in water pressure.This increased pressure causes the forces at the contact points between the sand particles to decrease. If the water pressure is high enough, it can reduce the interparticle forces to zero, which means that the sand particles ﾒfloatﾓ away from each other. For a brief time, the sand particles are suspended in the water. This is liquefaction. The soilﾕs loss of strength occurs because thereﾕs no contact between the particles of sand.So What?
Many buildings in the San Francisco Bay Area are built on landfill, sand, or mud that can liquefy. Liquefaction caused much of the damage during the 1989 Loma Prieta earthquake. It has also been responsible for major destruction in other quakes, including Kobe, Japan, in 1995 and Mexico City in 1985.
Amplitude of oscillation increasing

54. Solid bedrock is the best rock to build upon
Solid bedrock is the best rock to build upon. As the rock becomes softer, the damage done by earthquakes increases.

55. 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

56. 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.

57. An exemplary Model
The Hagia Sophia in Istanbul, Turkey has survived all magnitudes of earthquakes for nearly 1,500 years.