Questions for Earthquakes Part 1
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School
Chaffey College *
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Course
101
Subject
Geography
Date
Dec 6, 2023
Type
Pages
5
Uploaded by DeaconSwanMaster597
Earthquakes Part I PowerPoint Q&A
Directions:
Write your answers on the line below the question and be sure to highlight,
change colors, or underline the answer to make it easier to read.
1. Why can rocks bend?
If rocks are put under pressure, they will deform
2. When you pull hard on a rubber band and it snaps, what do scientists call that
action?
Elastic limit
3. What is a simple definition of stress?
a force applied over an area
4. What is causing stress on the San Andreas fault?
The strain and stress on the land
5. On the map on slide #3, in which direction is the Pacific plate moving? Choose one:
N, NE, E, SE, S, SW, W or NW
NorthWest
6. On the same map, what is the closest ocean fracture zone to Los Angeles?
Murray fracture zone
7. What is the simple definition of strain?
the change is the size and shape (deformation) of the land
8. What is wrong with the railing in the photo of slide #3?
There’s a slight bend in the railing
9. Looking at the diagram in slide #4, summarize in simple language how the elastic
rebound theory works. (It’s a pretty simple theory!)
It bends and then snaps
10. What limit is reached at the moment a magnitude 8 earthquake occurs on the San
Andreas?
the continuous stress of the 2 plates trying to slide by causes the plates to bend for
about 120 years until the rocks snap
11. What is the word used to describe the offset after an earthquake when the bending
and stored energy have been released?
Elastic rebound
12. Roughly how often do earthquakes on the southern San Andreas occur?
164 years ago
13. The last time that SoCal had an earthquake on the San Andreas was 1857. Since
then the Pacific plate has moved about 27 feet to the northwest. What simple thing are
the rocks doing so that no earthquake has occurred?
It hasn’t been strained
14. Is the San Andreas primarily a strike-slip or a dip-slip fault?
Strike-slip
15. The Cucamonga fault is lifting up the San Gabriel mountains behind Chaffey. Is it a
strike-slip or a dip-slip fault?
Strike-slip
16. In slide #6, is the fault shown right or left lateral? Check slide #7 if you are unsure.
Both
17. Going back to slide #5, in the strike-slip picture, is the fault right or left lateral?
Right lateral
18. Looking at slide #8, which fault shown is left lateral? A or B
B
19. In a normal fault, does the hanging wall move up or down?
Down
20. What is an alternative name for a reverse fault?
Thrust fault
21. What type of fault is the Cucamonga fault?
Reverse fault
22. The San Jacinto mountains are caught in a vise between the Pacific plate colliding
with the North American plate at a bend on the San Andreas. Are the San Jacinto
mountains rising on normal or reverse faults?
Normal faults
23. The Sierra Nevada mountains are rising because they are experiencing a stretching
force that extends all the way to the mountains above Salt Lake City. Are the faults
causing the Sierras to rise normal or reverse faults?
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Normal faults
24. Do reverse faults occur at divergent or convergent boundaries?
Convergent boundaries
25. Looking at slide #11, which is the normal fault? A or B
A
26. What is the difference between a thrust fault and a reverse fault?
The angle of the fault
27. Looking at the diagram on slide #12, what is the approximate angle of the fault?
Choose one: 10, 30, 60 or 90 degrees.
30 degrees
28. at least 100 homes are sitting directly on the San Andreas fault in SoCal. Which of
the 3 energy releases in slide #13 would be most damaging to a home sitting directly on
the fault?
Rock breakage, heat release, and seismic energy
29. There was a magnitude 6.5 earthquake in May near Tonopah, Nevada. The ground
started breaking at a depth of 1.7 miles below the surface. Is this depth an epicenter or
focus for the earthquake?
Focus
30. On October 16
th
, 1999, at 2 a.m. there was a magnitude 7.1 earthquake out in the
Mojave desert that derailed an Amtrak train. This earthquake occurred in a remote
place with the closest named landmark being the Hector mine. Would Hector Mine be
the epicenter or focus of this earthquake?
Epicenter
31. On slide #14, does the diagram depict a normal or reverse fault?
Normal fault
32. The San Andreas fault is a transform boundary where 2 plates are trying to slide by
each other. So why is the San Andreas also behaving like a reverse fault in southern
California? See slide #15.
Because of compression
33. Looking at the map on slide #15, at which town does the San Andreas begin its “Big
Bend”?
Cape Mendocino
34. On slide #16, what is causing compression on the Big Bend segment of the San
Andreas?
The right lateral San Andreas fault (SAF) makes a left bend when viewed towards the
northwest.
35. If the Death Valley fault system is also right lateral like the San Andreas fault, then
why is a pull-apart basin being created rather than a mountain range?
These faults are helping the Pacific plate move northwest.