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Week 2 Earthquakes Lab Report
GLG/220 Version 3
1
University of Phoenix Material
Week 2 Earthquakes Lab Report
Answer the lab questions for this week and summarize the lab experience using this form.
Carefully read Ch. 9 of Geoscience Laboratory. Pay special attention to the graphs and figures.
Complete this week’s lab by filling in your responses to the questions from Geoscience Laboratory.
Select answers are provided for you in red font to assist you with your lab work.
Questions and charts are from Geoscience Laboratory, 5th ed. (pp. 155–167), by T. Freeman, 2009, New
York, NY: John Wiley & Sons. Reprinted with permission.
Lab Questions
9.1.
Judging from the seismogram in Figure 9.4 of the lab book, which wave appears to be the most
damaging?
Take a look at Figure 9.4 and 9.5 which are reproduced below. Remember that an earthquake
produced both P and S waves, but these waves arrive at a seismic station at different times.
Figure 9.5 plots the information (dashed lines indicating travel-time and a seismogram image) for
an earthquake with a difference in arrival times of P and S of 7.2 minutes (question 9.3 will ask
you to think about P and S waves that arrive 5 minutes apart).
Note. The S-wave arrival time is erroneously labeled as 16. Please note that it is actually 16.7.
(This is corrected below.)
9.3.
Determine the distance to an earthquake at a station that receives P and S waves 5.0 minutes
apart. Refer to the Figures 9.4 and 9.5, reproduced below. Hint: (a) Place tick marks on a scrap of
paper equal to 5.0 on the minutes axis. (b) Fit that to the horizontal separation between P and S
curves. (c) Read distance directly across on the distance axis.
Remember your goal is to find where the P and S wave curves are 5 minutes apart. The scrap of
paper is helpful when you find where the P and S curves are 5 minutes apart—then you can
follow you piece of paper over to the vertical axes (distance traveled) and see how many
kilometers the earthquake station is from the earthquake.
Copyright © 2014, 2011 by University of Phoenix. All rights reserved.
Week 2 Earthquakes Lab Report
GLG/220 Version 3
2
From Geoscience Laboratory, 5th ed. (p. 155), by T. Freeman, 2009, New York, NY: John Wiley & Sons.
Reprinted with permission.
Copyright © 2014, 2011 by University of Phoenix. All rights reserved.
Week 2 Earthquakes Lab Report
GLG/220 Version 3
3
From Geoscience Laboratory, 5th ed. (p. 155), by T. Freeman, 2009, New York, NY: John Wiley & Sons.
Reprinted with permission.
9.4.
At this point, from the information in Figure 9.6A, how specific can you be as concerns the
location of that earthquake?
Answer: The earthquake is somewhere on the circle around Seattle (Hint: You can be more
specific with regards to the location when you have information from more than one seismic
station).
9.5.
At this point, from the information in Figure 9.6B, how specific can you now be as concerns the
location of that earthquake?
9.6.
At this point, from the information in Figure 9.6C, how specific can you now be as concerns the
location of that earthquake?
9.7
The effect of value III in Table 9.1 is ‘Felt indoors.’ Why specify indoors? Why should eye witness
accounts indoors differ from eye witness accounts outdoors? Hint: Consider the surroundings.
Copyright © 2014, 2011 by University of Phoenix. All rights reserved.
Week 2 Earthquakes Lab Report
GLG/220 Version 3
9.10.
4
Using the nomogram, determine the Richter magnitude for the three earthquakes listed (see p.
169 of Geoscience Laboratory).
S arrival minus P arrival
Amplitude
(A) 8 seconds
(B) 8 seconds
(C) 6 seconds
20 millimeters
0.2 millimeters
10 millimeters
Magnitude
9.14.
The 2002 Afghanistan earthquake measured 5.9 on the Richter scale and killed 1,800 people.
The 2001 western Washington earthquake measured 6.8 on the Richter scale and killed only one
person. Can you imagine why there is a huge difference in the numbers of deaths? Hint: It has to
do with construction materials.
9.17.
Where is the location of that June 19 quake (to the nearest tenth of a degree latitude and
longitude)? Follow the steps 1 through 4 to complete the table below (refer to and complete
Appendix D, reproduced from Geoscience Laboratory, Ch. 9).
P arrival time
LTN
GOIL
POW
S arrival time
hours: minutes: seconds tenths of
seconds
3:46:45.7
3:46:50.0
3:47:17.2
3:47:3:0
Difference in P & S
Distance
seconds
kilometers
4.3
35.6
9.17 Latitude Answer: 36.3º
9.20.
One of the curious things about the loss of life in regions surrounding the Bay of Bengal is that
some 38,195 lives were lost in Sri Lanka, whereas only 2 lives were lost in Bangladesh. How
could this be? It certainly couldn’t be the difference in distance. Hint: To answer this question, you
should first contour the map in Figure 9.20 (see p. 170 in the lab book) and then follow ‘the rule.’
Note. You do not need to submit the contour map with this report.
Lab Summary
Address the following in a 100- to 200-word summary:
•
•
•
•
Summarize the general principles and purpose of the lab.
Explain how this lab helped you better understand the topics and concepts addressed this week.
Describe what you found challenging about this lab.
Describe what you found interesting about this lab.
Write your summary here:
Copyright © 2014, 2011 by University of Phoenix. All rights reserved.
Earthquakes are produced by abrupt motion along a fault when friction that
resists such motion is overcome by stress (Fig. 9.1). This is called elastic
rebound. It’s quite analogous to the bending and breaking of a green twig.
Some 21 feet of abrupt adjustment along the San Andreas Fault generated
the fateful San Francisco earthquake of 1906.
Figure 9.1 Some 21 feet of plastic strain across the San Andreas fault—
exhibited here by distorted utility lines and such—accumulated before
the correction of 1906.
Most earthquakes are produced by movement along a fault. But movement
is not along the entire fault during any one event. Instead, movement involves
a region of the fault measured in a few kilometers. The place within that region
where movement first occurs is called the focus. But of more interest to
people is the spot on the ground directly above the focus, which is called the
epicenter. The epicenter equates with the spot where there is maximum
ground motion and maximum damage.
Figure 9.2 Three seismic waves consist of one surface wave and two
penetrative body waves.
Surface wave. Rolling of rock particles (arrows) in response to
passage of a moving wave. The wave form is much like that of water
particles within a wave in that particle motion diminishes downward.
Primary or P wave. Motion of rock particles (arrow) is parallel to the
direction of energy transmission. The wave form is that of
compression and relaxation of rock, a bit like a Slinky™ toy.
Secondary or S wave. Motion of rock particles (arrow) is
perpendicular to direction of energy transmission. Standing waves
result, like the distortion of a trampoline.
Figure 9.3 A seismograph is designed so that during an earthquake
there is motion between rotating paper and an ink pen. (A) A
seismograph before an earthquake. (B) A seismograph during an
earthquake.
Figure 9.6 Three-step procedure for determining the location of an
eartquake.
Figure 9.7 Three spheres whose volumes are proportionately equal to
Richter magnitudes 1.0, 2.0, and 3.0.
Figure 9.17 Locations of the epicenter of an earthquake and an array of
five stations within a system of pressure sensors.
Figure 9.20
For answering Q 9.10
To Answer Q 9.20 use this
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