SO503 Spring
2005
Test 2
Exam makeup
|
Short
answers |
4
of 5, 10 points each |
40 |
|
|
Problems |
4
at 15 points each |
60 |
|
|
Total |
|
100 |
|
Short
Answers: Answer 4 of the following 5 of the questions with a few
sentences. Each is worth 10 points.
When
is lossy compression worthwhile?
Why
are so many scientists concerned about the possibility of a manned mission to
Mars?
Why
has EOS had so many references to the great megathrust earthquake of 2004?
What
events can cause tsunamis, and what are the challenges in setting up warning
systems?
How
can tidal signals show up in rocks millions of years old?
The
graph below shows a time series, with a reading taken every day for 1255 days.
Problem
1, 15 points. The next page shows
the results of an FFT run on the time series.
Results
of an FFT run on the data, with the bins sorted by Power (top) and Period
(bottom).
Bin
Frequency
Period
Power
1 0.0
infinite 83.638870
6 0.00293
341.333333 5.451275
5 0.00244
409.600000 5.094719
3 0.00146
682.666667 5.062107
4 0.00195
512.000000 3.227708
293 0.14307
6.989761 3.187808
2 0.00098
1024.000000 2.551096
292 0.14258
7.013699 2.136037
10 0.00488
204.800000 1.647327
9 0.00439
227.555556 1.577684
585 0.28564
3.500855 1.176392
294 0.14355
6.965986 1.150024
7 0.00342 292.571429
0.967016
26 0.01270
78.769231 0.757571
586 0.28613
3.494881 0.667365
Bin
Frequency
Period
Power
1 0.0
infinite 83.638870
2 0.00098
1024.000000
2.551096
3 0.00146
682.666667 5.062107
4 0.00195
512.000000 3.227708
5 0.00244
409.600000 5.094719
6 0.00293
341.333333 5.451275
7 0.00342
292.571429 0.967016
8 0.00391
256.000000 0.351580
9 0.00439
227.555556 1.577684
10 0.00488
204.800000 1.647327
Problem
2, 15 points. This shows the result
of fitting Fourier curves to try to replicate the time series, sorted by
amplitude. Note the large number of
periods near 1 day, the sampling interval.
Are these meaningful according to Nyquist?
Component
Period Phase
Amp % SS
Cum % SS
3 418.333
141.2 20.703
5.485 5.49
1252 1.002
38.8 20.703
5.485 10.97
179 7.011
300.1 20.513
5.385 16.36
1076 1.166
59.9 20.513
5.385 21.74
1253 1.002
34.0 19.102
4.670 26.41
2 627.500
146.0 19.102
4.670 31.08
1075 1.167
86.8 19.003
4.621 35.70
180 6.972
93.2 19.003
4.621 40.32
1254 1.001
306.6 17.947
4.122 44.45
1 1255.000
53.4 17.947
4.122 48.57
1251 1.003
279.2 15.631
3.127 51.70
4 313.750
80.8 15.631
3.127 54.82
358 3.506
2.4 12.341
1.949 56.77
897 1.399
177.6 12.341
1.949 58.72
1239 1.013
312.6 11.953
1.829 60.55
16 78.438 47.4 11.953
1.829 62.38
Problem
3, 15 points. Explain what this
graph showing an autocorrelation means.
The second graph is a blow up of the left side of the first graph.
Could it be the same data set seen in the last problem?
Why or why not.
/
Problem
4, 15 points. The graphs below show
the trends of average yearly and monthly sea level at Annapolis from
approximately 1930 to 2000, from http://www.pol.ac.uk/psmsl/psmsl_individual_stations.html
.