1. EARTHQUAKES
Objective: Determine where earthquakes are most likely to occur and provide evidence.

2. What Causes Earthquakes?
When rock reaches its elastic limit an earthquake occurs.
Rock can stretch farther without breaking than steel can, but rock will break at some point.
Elastic Rebound: the sudden “bounce – back” of rock to its original shape
like the return of the broken rubber-band to its unstretched shape.
During elastic rebound, rock releases energy.

5. What do you notice about the location of the earthquakes/volcanoes?
Why?

6. Where do earthquakes occur?
Occur at plate boundaries
What are the three types of boundaries?
Convergent: Plates move together
Divergent: Plates move apart
Transform: Plates are sliding

7. Fault Lines When rock breaks, they move along surfaces called faults.
3 Types of faults
Normal
Reverse
Strike/Slip

8. Normal fault Force applied = Tensional
Movement = Rock above fault moves downward.
Before After
What plate boundary is a normal fault similar to?
Divergent

9. Normal Fault
Hanging wall slides below the foot wall.

10. Reverse Fault Force applied = Compressional
Movement = Rock above fault moves Upward.
Before After
What boundary is a reverse fault similar to?
Convergent

11. Strike/Slip fault Force applied = Shearing
Movement = Rocks slide past each other.
Energy builds up until elastic limit is reached = Earthquake
Before After
What boundary is a strike/slip fault similar to?
Transform

12. Strike/Slip Fault Strike/Slip fault show how the fault line will
cause the 2 sides to
not line up.

13. San Andreas Fault- Transform fault
Rocks of the Pacific Plate (gray rocks on the left side of the fault) and the North American Plate (tan rocks on the right side of the fault).

14. Determining distance to Epicenter
Epicenter – The location of an earthquake on the surface of the Earth above the focus.
Focus – Location within the Earth’s crust where the breaking of rock occurs
Surface

15. Seismic waves
The vibrations caused by the breaking rock are called seismic waves.
These waves travel through the Earth creating damage on the surface.

16. Seismic Wave Analysis P-Wave Analysis
What do you notice about the motion of this wave?
Do you think this wave is traveling quickly or slowly?
Does this wave do a lot of damage to the house?

17. Primary waves Compress and stretch (ex:spring) Fastest moving waves
Cause rock to move back and forth in the same direction the wave is moving.

18. S-Wave Analysis What do you notice about the motion of this wave?
Do you think this wave is traveling quickly or slowly?
Does this wave do a lot of damage to the house?

19. Secondary waves move up and down like an “s” Second fastest wave
Cause rock to move up and down at a right angle to the direction the wave is moving

20. L-Wave (Surface Wave) Analysis
What do you notice about the motion of this wave?
Do you think this wave is traveling quickly or slowly?
Does this wave do a lot of damage to the house?

21. Surface waves When energy reaches the earth’s surface.
They move up and down and side to side.
They move the slowest.
They cause the most damage.

22. Do now
Fault
Force

23. Global Earthquakes from Jan. through Apr. 2014
This animation shows all earthquakes on earth so far this year in sequence as recorded in the USGS’s NEIC database (available at earthquake.usgs.gov). Note the typical level of activity through March. But starting with the 8.2 magnitude earthquake in northern Chile on April 1, the rest of the month saw 12 more moderate-to-large earthquakes mostly in Chile and the Solomon Islands but also in Nicaragua, Mexico, Canada, and even the south Atlantic Ocean. The animation concludes with a summary map showing all of the earthquakes in this four-month period.

24. Three Waves Together P-, S-, and L-Waves Together
Do you notice any differences in each wave types motion?
Which wave travels the quickest? Slowest?
Which wave does the most damage? Why do you think this is?

25. How is this information Useful?
Scientists use the different speeds of the seismic waves to find the distance to the Epicenter.

26. 3mph
They start out together
As time goes by they will
Get further and further
Apart.
So, the longer they ride, the
Further apart they will get
7mph
What happens to the distance between them as time goes by?

27. How can we apply this to seismic waves?
Do the waves start together?
Which wave will arrive first?
Second?
Third?
What does the distance in arrival times tell us?

28. Primary waves arrive first
Then secondary
Then surface waves
The farther apart the waves
Arrive, the farther away the
Epicenter is.

29. Seismograph stations
Seismologists are scientists that study seismic waves.
There are seismograph stations all over the earth recording seismic waves.

30. Seismogram Which wave arrives first? Second? Last?
Did they all start at the same time?

31. Primary waves arrive first
Then secondary
Then surface waves
The farther apart the wave
Arrivals, the farther away the
Epicenter is.

32. P – S Wave Chart
Chart can be used to determine arrival times of P and S waves.
Can also be used to located the distance to the epicenter from the seismic station.

33. This represents TIME (in minutes!)
Notice the vertical axis
This represents TIME (in minutes!)
Let’s enlarge a small section

34. 20 Between each minute, we notice that there are 3 segments.
If there are 60 seconds in a minute, each one of these segments must be ________seconds. 20

35. What would this time be?
2 minutes, 20 seconds

36. This represents DISTANCE (in thousands of Kilometers!)
Notice the horizontal axis
This represents DISTANCE (in thousands of Kilometers!)
Let’s enlarge a small section

37. So what would this distance be?
Fill these in...
5,400km

38. There are also two curves on this chart that display the way different earthquake waves behave.

39. S-Wave
P-Wave

40. This chart can be used for answering many different questions!
Let's try a few examples
How long does it take an S-Wave to travel 5,000km?
Go to the chart!

42. Another example... Go to the chart!
The recording station tells us it took 6 minutes and 20 seconds for the P-Wave to reach them. How far away from the epicenter of the earthquake must they be?
Go to the chart!

43. 3,600km

44. Another example... Go to the chart!
I know that there was a 7 minute difference in the arrival of my P and S waves. How far away from the epicenter must I be?
Go to the chart!

45. Slide your scrap paper up until the tick marks match up with the curves…
Mark off 7 minutes on scrap paper…

46. Example
Measure the difference in time of arrival of P- and S-Waves, then determine the distance the waves are traveling from using the graph

47. Difference in Arrival Times
If a P-Wave arrived at 3:00:00PM and an S-Wave arrived at 3:03:30PM, then what is the difference in arrival time?
If a P-Wave arrived at 3:51:15PM and an S-Wave arrived at 3:53:50PM, then what is the difference in arrival time?
00:03:30 (3 minutes and 30 seconds)
00:02:35 (2 minutes and 35 seconds)

48. After you get the difference, then go to the graph and get the distance.
3 minutes and 30 seconds
2 minutes and 35 seconds
2,200 km (2.2 x 103)
1,400 km (1.4 x 103)

49. Then, draw a circle around each station with a radius that equals the distance from the earthquake
The epicenter can be anywhere on the circle, so
How can we figure out exactly where it is?

50. You need at least 3 stations to determine the epicenter

51. LIST THE STEPS TO LOCATE THE EPICENTER OF AN EARTHQUAKE
1. Find the difference in travel time between P and S waves
2. Use the graph to find where the P and S waves are that time apart.
3. Read the distance on the x-axis.
4. TO DETERMINE THE EXACT LOCATION OF AN EPICENTER, you must have 3 seismic stations recording the same earthquake

52. Measuring earthquakes
Magnitude: the measure of the amount of energy released by an earthquake.
2 ways to measure earthquakes.

53. Richter scale
Measures how much energy is released based on seismic waves.
It deals mainly with the strength of the break, not the size of the fault.
Ranges from 1 to approximately 10.
The higher the number the stronger the seismic waves.

55. Modified Mercalli scale
Measures the amount of damage done by the earthquake.
The more damage the greater the rating.

56. What can people do to prepare for an earthquake?
Make your home earthquake safe
Take down heavy objects from high places
Secure gas appliances and hot-water heaters
Keep away from windows during earthquake
Watch for fallen power lines and fire hazards.
Keep emergency kits available
Batteries, water, flashlights

57. volcanoes An opening in the earth’s surface where magma rises
A mountain is formed from layers of lava and volcanic ash

58. Magma vs lava Magma: Molten rock under the earth’s surface
Lava: molten rock above the earth’s surface

59. Most volcanoes are now dormant
(not currently active), about 600
Are now active.

60. Where do volcanoes occur?
1. Divergent plates: Moving apart
Ex: mid atlantic ridge
Creates rifts where magma flows out as lava and is cooled by seawater.
Islands are formed (iceland)

61. Convergent plates: Plates moving
Together.

62. 3. Hot spots: Plates do not meet here
Some areas of the mantle are hotter than
Others. These hot spots melt rock,
Which is then forced up as magma.
Hawaiian islands
The pacific plate is
Moving over the hot
Spot. Kuai is the
Oldest island.

63. Types of volcanoes
Some volcanoes erupt violently, some erupt quietly. Why?
Due to the amount of trapped gas: water vapor and CO2.
The more trapped gas, the greater the explosion ( ex: soda can)

64. Magma composition Magma contains Silica
More Silica  thicker magma  traps more gas  greater explosion