The AS-1 Seismograph – Operation…
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The AS-1 Seismograph –
Operation, Filtering, S-P
Distance Calculation, and
Ideas for Classroom Use 1
L. Braile, November, 2002;
Updated November, 2004
[email protected]
http://web.ics.purdue.edu/~braile
Examples of Recorded Seismograms and Filtering of Seismograms: The AS-1
seismometer (Figure 1) has a natural period of oscillation of about 1 s. To make the seismometer
more useful for recording local as well as distant earthquakes, the amplifier unit supplied with the
AS-1 uses strong filtering to enhance the long period (greater than 10 s period) response of the
instrument. The combined response of the seismograph is more broadband and can record signals
ranging from about 30 s period to 2 Hz (0.5 s period). Local and regional (within about 1200 km or
10 degrees distance from the seismograph location) earthquake seismograms are usually dominated
by short period (near 1 s period) energy. Teleseismic (distant earthquakes, 10 to 180 degrees)
recordings usually consist of lower frequency (longer period) energy and often have prominent
surface wave arrivals of 12 – 30 s period. Microseisms are a nearly universal source of ground
noise in seismic recording and have periods of about 3 – 8 s. Because this period range is amplified
strongly by the AS-1 seismograph, filtering of the records is often desirable to enhance the
earthquake signals. A useful filter for local and regional events (short period) is a bandpass filter
with frequency cutoffs of 0.5 Hz to 3 Hz (frequency in cycles per second, or Hertz, is equivalent to
1/Period in seconds, so these cutoffs are the same as 2 s period and 0.333 s period; in the AmaSeis
control menu, after the seismogram is selected or extracted, enter the two frequencies, lowest
frequency is cutoff one, highest frequency is cutoff two). An example of use of a short period filter
is shown in Figures 2 and 3 for an earthquake that was located 2.63 degrees (~292 km) from the
station.
1
Last modified November 21, 2004
The web page for this document is:
http://web.ics.purdue.edu/~braile/edumod/as1mag/as1mag2.htm.
Partial funding for this development provided by IRIS and the National Science Foundation.
© Copyright 2002-4. L. Braile. Permission granted for reproduction for non-commercial uses.
The AS-1 Seismograph – Operation…
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Figure 1. The AS-1 seismometer showing the main components of the instrument. The AS-1 is a vertical
component seismometer. Up and down motions of the ground, and therefore of the base and frame of the
seismometer, cause the coil to move relative to the magnet that is suspended by the spring and boom
assembly. The mass of the seismometer, consisting primarily of the magnet and the washers, tends to remain
steady because of inertia when the base moves. The motion of the coil relative to the magnet generates a
small current in the coil. The current is amplified and digitized by an amplifier unit (not shown) and
connected to the computer for recording and display. The damping (using oil in the container and a washer
mounted to a bolt extending downward from the boom into the oil) reduces the tendency for the mass and
spring system to oscillate for long duration from a single source of ground motion (arrival of seismic waves
at the location).
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Figure 2. AS-1 seismogram recorded at West Lafayette, Indiana from an earthquake located near
Evansville, Indiana, December 7, 2000. The earthquake epicenter was about 292 km away from the
seismograph and had a magnitude of about 3.9 (mbLg). Microseisms of about 3-6 second period are visible
before the first arrival (the compressional or P wave) that is located at about 1.1 minutes (relative time).
The S (Shear) wave and surface waves are the largest arrivals following the P wave.
Figure 3. Seismogram for the Evansville earthquake (Figure 2) after filtering (0.5 – 3 Hz cutoffs) to enhance
the high frequency energy of the earthquake signal. The P, and S and surface wave arrivals are recognized
The AS-1 Seismograph – Operation…
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partly by the frequency contrast and are slightly enhanced, as compared to the background microseism noise
and the unfiltered seismogram shown in Figure 2, on the filtered seismogram.
For teleseismic or distant earthquakes, lower frequency filtering often enhances the seismogram,
especially the surface wave arrivals that are prominent for shallow focal depth (0 – 70 km depth)
earthquakes. Suggested filter cutoffs for lower frequency (longer period) signal enhancement are
0.01 Hz (cutoff one) to 0.2 Hz (cutoff two), equivalent to a 100 s to 5 s period range. Because the
seismograph has very low response at very low frequencies, the lowest frequency cutoff (0.01 Hz)
is intended primarily to avoid amplitude distortion and offset of the zero level of the trace that is
sometimes caused by filtering the extracted trace. An example of the advantages of filtering
seismograms to enhance the long period energy is shown in Figures 4, 5 and 6. Figure 4 is the
AmaSeis screen display for a 24 hour record (each horizontal trace is one hour long; the display is
designed to look like the familiar drum recording on paper; hours scale is along the left side;
minutes scale is at the bottom) including an earthquake that occurred at 11:41:47.9 (Greenwich
Mean Time, GMT), August 9, 2000, in Michoacan, Mexico. The event had a magnitude of 6.5
(surface wave magnitude, MS) and was located about 25.96 degrees (2887 km) from the
seismograph at West Lafayette, Indiana. The extracted seismogram (Figure 5) shows a close-up
view of the earthquake signal.
Figure 4. AS-1 seismograph recording for August 9, 2000, Michoacan earthquake.
The AS-1 Seismograph – Operation…
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Figure 5. Extracted seismogram for the Michoacan earthquake. Amplitude scale is in count or digital units.
The filtered seismogram (Figure 6) enhances the main arrivals and makes it much easier to
determine arrival times. Filtering using the control menu in AmaSeis can be performed more than
once to further enhance the frequency range of interest.
The AS-1 Seismograph – Operation…
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Figure 6. Extracted seismogram for the Michoacan earthquake after bandpass filtering (0.0001 Hz and 0.1
Hz cutoff frequencies) to enhance the long period (10,000 – 10 s) energy. The P wave arrival (the first
arriving energy is at about 3 minutes, relative time, followed about 40 s later by the PP arrival. The PP
phase is a P wave that reflects from the Earth’s surface once near the halfway distance between the
epicenter and the seismograph station. The S (shear) wave arrives at about 7.5 minutes and is visible partly
because of the frequency change (lower frequencies often characterize the shear waves). Prominent surface
waves (Rayleigh waves) are visible at about 14 – 15 minutes relative time.
S-P Distance Calculation: The AmaSeis software includes a useful tool for determining the
epicenter-to-station distance from the S-P arrival time difference on seismograms. For AS-1
seismograms extracted from a 24 hour record or saved as SAC files, or for SAC format
seismograms downloaded from the internet, the AmaSeis arrival time picking tool can be used to
mark the interpreted arrival times of the P and S waves (Figure 7). Then, by selecting the travel
time curve tool, the seismogram is displayed on standard travel time curves. By moving the
seismogram on the screen, the interpreted P and S times can be aligned with the arrivals on the
travel time curves (Figure 8). The S-P times can also be analyzed using standard travel time curves
(Bolt, 1993, p 134; or from the internet at http://lasker.princeton.edu/index.shtml). Once aligned, the
epicenter to station distance is determined and displayed.
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Figure 7. Vertical component seismogram from GSN station KIP for the September 30, 1999 Oaxaca
earthquake. The SAC file was downloaded using the IRIS WILBER tool. The seismogram was displayed
using AmaSeis and the P and S arrival times (vertical red lines) picked.
The AS-1 Seismograph – Operation…
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Figure 8. KIP seismogram from Figure 7 displayed with the travel time curve tool in AmaSeis. In this tool,
the seismogram can be moved around on the screen until the selected P and S arrival times are aligned with
the travel time curves. The epicenter-to-station distance corresponding to the observed S-P time is then
determined by the position of the seismogram and the specific distance, in this case 58.72 degrees, is
displayed adjacent to the distance axis.
Using seismograms from three or more stations, the location of the epicenter can be estimated by
triangulation. For example, for the September 30, 1999 Oaxaca earthquake, seismograms for
stations KIP, BINY, COLA and AMNO were displayed in the AmaSeis program, the P and S
arrival time picked, and the epicenter to station distances inferred. Using an inflatable globe,
circular arcs are drawn on the globe corresponding to the epicenter-to-station distance for each
seismograph station (Figure 9). When all arcs have been drawn, the approximate epicenter location
is determined by the intersections of the arcs (Figure 10). Although this triangulation method is not
the most reliable or accurate technique for locating earthquakes, it is relatively easy to understand
and illustrates concepts of the travel times of seismic waves at increasing distances and earthquake
location methods.
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Figure 9. Using a piece of string marked at the appropriate distance in degrees (measure along the equator)
and a felt pen (water soluble ink), a circular arc is drawn on an inflatable globe using the seismograph
station (in this case, station AMNO) as the center of the circle. Arcs are also drawn for other stations using
the appropriate distances inferred from the S-P times.
The AS-1 Seismograph – Operation…
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Figure 10. After all arcs have been drawn, the epicenter is inferred by the approximate intersection of the
arcs. Because of inaccuracies in the estimation of the S-P times and drawing the arcs on a globe, the
intersections of the arcs may not be exactly a single point. However, a reasonably good location is
determined by this method.
Because the S wave arrival is not always prominent on a vertical component seismogram, the
epicenter-to-station distance cannot always be inferred from AS-1 seismograms. Furthermore, for
seismograms from earthquakes that are located greater than 105 degrees from the station, no direct
S wave arrivals are present due to the Earth’s core. For earthquakes recorded at the West Lafayette,
Indiana AS-1 station since April, 2000 (Table 1), distances inferred from the AS-1 seismograms are
compared with the calculated distances (from the USGS reported epicenter to the station location)
in Figure 11. Although the distances generally correspond, the AS-1 distance determination appears
to be accurate to only about +/- 4 degrees distance for distances greater than about 20 degrees.
More information on using the AmaSeis software is available at:
http://web.ics.purdue.edu/~braile/edumod/as1lessons/UsingAmaSeis/UsingAmaSeis.htm.
minus P earthquake location exercise is available at:
http://web.ics.purdue.edu/~braile/edumod/as1lessons/EQlocation/EQlocation.htm.
An S
The AS-1 Seismograph – Operation…
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Figure 11. Comparison of calculated distances (using station location and USGS epicenter location) with
distance estimated from the S-P times on seismograms recorded by the AS-1 seismograph. Distance
estimates from the S-P times were determined using the travel time curve tool in AmaSeis. Comparing actual
and AS-1/AmaSeis S-P calculated distances. N = 75; Standard Deviation = 2.51 degrees (November, 2004).
Ideas for Classroom Use: Operating an AS-1 seismograph in a classroom or school building
encourages awareness of earthquake activity around the world and provides an opportunity for
teachers and students to work with real scientific data. There is particular interest and excitement
when a local or regional event occurs and is recorded by the seismograph or when a significant
distant event happens. Students will be interested in “checking the seismograph” each day and
seeing how their records and magnitude estimates compare with the seismograms recorded at other
stations and official magnitudes. The occurrence of significant earthquakes around the world (there
are about 20 events per year of magnitude of 7 or greater: many of these events cause significant
damage) can be used to stimulate discussion, learning and research on geography, the causes of
earthquakes, propagation of seismic waves, earthquake hazards, and earthquake safety. Some
specific suggestions for classroom use are:
1. Maintain a catalog of seismograph recording. Students can check the seismograph every
day (or at regular intervals), perform routine maintenance (check that it is operating properly
and perform a time check), identify possible recorded events and enter appropriate
information into the catalog. A hand written catalog is sufficient for recording such
information as time corrections and approximate times of recorded events. A more
The AS-1 Seismograph – Operation…
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complete catalog can be created using a spreadsheet (see Table 1, below) with information on
earthquake to station distance and magnitudes. Distance from the earthquake epicenter can be
inferred from the P and S travel times as described above (AmaSeis provides a simple tool for
performing this estimation; these times will not be able to be determined for all recorded
events). Magnitudes can be estimated using the procedures described in The AS-1 Seismograph
– Magnitude Determination or using the online magnitude calculator at:
http://web.ics.purdue.edu/~braile/edumod/MagCalc/MagCalc.htm. A comparison between the
AS-1 distance and magnitude information can be made by checking the USGS/NEIC, IRIS
event search or IRIS seismic monitor sites on the Internet. Instructions for accessing earthquake
data on the Internet are included in
http://web.ics.purdue.edu/~braile/edumod/eqdata/eqdata.htm. All data should be written in the
catalog to provide a record of activity of your seismograph station and document the
comparison of distance and magnitude determinations.
Exercises that include magnitude calculations using AS-1 seismograms are available at:
http://web.ics.purdue.edu/~braile/edumod/as1lessons/EQlocation/EQlocation.htm and
http://web.ics.purdue.edu/~braile/edumod/as1lessons/magnitude/CalcMagnElect.htm.
The AS-1 Seismograph – Operation…
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Table 1. Earthquake List -- Events recorded by AS-1 Seismograph, West Lafayette (40.44N, 86.90W) Indiana (L. Braile)
DATE
TIME(GMT)
LAT
LON
DEP.
USGS
USGS
USGS
USGS
AS1
AS1
AS-1
Calc.
Dist
AS-1
Dist
MM/DD/YY
HR:MN:SS
Deg.
Deg.
(km)
mb
MS
Mw
mbLg
mb
MS
mbLg
Deg.
Deg.
01/01/00
11:22:57
46.888
-78.930
18
4.7
05/04/00
4:21:16
-1.110
123.570
26
6.7
05/12/00
18:43:18
-23.550
-66.450
225
6.2
06/02/00
11:13:49
44.510
-130.080
10
5.8
5.7
06/04/00
16:28:26
-4.720
102.090
33
06/21/00
0:51:47
63.980
-20.760
10
6.1
6.6
07/11/00
1:32:29
57.370
-154.210
43
6.3
08/04/00
21:13:03
48.790
142.250
10
6.3
08/06/00
7:27:13
28.860
139.560
394
6.3
5.2
7.5
5.2
7.6
7.0
7.2
6.5
6.2
5.8
6.0
8.0
6.1
7.3
08/07/00
14:33:56
-7.020
123.360
648
6.5
08/09/00
11:41:48
18.200
-102.480
45
6.1
6.5
6.4
08/22/00
20:12:14
36.490
-91.110
10
08/28/00
15:05:48
-4.110
127.390
16
6.5
6.8
6.8
08/28/00
19:29:32
-4.120
127.030
33
6.5
6.4
6.4
09/28/00
23:23:43
-0.220
-80.580
22
5.8
6.0
6.6
65.3
Argentina
5.5
31.830
32.9
Coast Oregon
7.6
143.490
6.7
44.230
45.2
Iceland
45.350
47.3
Kodiak Is., AK
81.080
81.6
Sakhalin Is.
Bonin Is.
Region
6.1
6.7
7.1
137.100
5.8
25.960
3.9
2:25:31
-7.980
30.710
34
10/04/00
14:37:44
11.120
-62.560
110
10/04/00
16:58:44
-15.420
166.910
23
6.1
6.9
6.8
10/25/00
9:32:24
-6.550
105.630
38
6.3
6.6
6.8
11/01/00
4:27:46
-7.910
-74.470
151
5.9
11/06/00
11:40:29
56.300
-153.350
33
5.5
11/16/00
4:54:56
-3.960
152.270
33
11/16/00
7:42:17
-5.180
152.050
11/17/00
21:01:56
-5.450
151.680
12/06/00
17:11:07
39.620
12/07/00
14:08:49
01/10/01
01/13/01
3.6
6.6
5.180
132.440
5.6
6.5
5.6
40.920
6.6
116.050
6.3
6.9
Sunda Arc
Peru-Brazil Bor.
Reg.
5.6
49.490
6.0
8.2
33
6.2
33
6.2
54.770
30
6.7
37.930
-87.710
11
16:02:42
57.090
-153.620
33
6.2
6.8
6.8
5.8
13:08:41
40.740
-125.330
5
5.3
5.2
5.6
5.7
01/13/01
17:33:31
12.830
-88.790
39
6.7
7.8
7.6
6.5
01/16/01
13:25:00
-3.970
101.660
33
6.7
6.8
01/18/01
1:40:48
25.880
-110.380
10
5.0
5.0
24.370
01/23/01
5:23:37
13.920
-90.990
120
5.7
5.4
26.710
01/26/01
3:03:19
41.990
-80.830
5
01/26/01
3:16:41
23.400
70.320
24
02/13/01
14:22:08
13.650
-88.990
13
5.7
6.4
02/13/01
19:28:27
-5.080
102.440
36
6.7
7.2
02/17/01
20:11:28
54.250
-133.610
10
5.6
5.9
02/24/01
7:23:49
1.460
126.290
33
6.6
7.0
02/26/01
5:58:23
46.920
144.410
394
5.8
02/28/01
18:54:33
47.150
-122.720
51
6.5
03/15/01
13:02:42
-32.321
-71.492
37
6.1
5.6
6.0
04/09/01
9:00:57
-32.668
-73.109
11
6.1
6.3
6.7
04/14/01
2:20:13
56.080
-119.810
10
5.3
4.7
5.3
04/19/01
21:43:42
-7.410
155.865
17
6.0
6.6
6.7
04/21/01
17:18:57
42.925
-111.395
0
5.4
4.9
5.3
5.6
18.450
04/29/01
21:26:55
18.736
-104.545
10
5.2
5.5
6.1
5.2
26.460
05/04/01
6:42:13
35.205
-92.194
10
05/20/01
4:21:44
18.816
-104.446
33
5.5
6.0
6.3
5.5
6.3
05/25/01
0:00:51
44.268
148.393
33
6.1
6.7
6.7
6.2
6.3
05/25/01
5:06:11
-7.869
110.179
143
5.8
5.6
45.040
8.0
7.8
115.760
7.8
7.8
7.3
116.020
8.0
7.8
7.6
117.200
7.5
7.0
7.2
3.9
6.4
6.6
7.5
27.550
6.6
142.880
7.8
6.8
6.3
27.6
Kodiak Is. Reg.
Off coast N.
California
Off coast C.
America
23.4
So. Sumatera
Gulf of
California
El Salvador
4.800
Ohio
112.990
6.0
26.800
7.1
143.710
29.9
El Salvador
So. Sumatera
Queen
Charlotte
Islands
6.1
33.930
128.450
N. Molucca Sea
6.1
81.730
5.9
26.530
Sea of Okhotsk
Nisqually
(Seattle, WA)
Near co Central
Chile
Off co Central
Chile
?
?
6.7
4.4
23.4
73.820
5.2
73.900
75.3
26.620
28.5
Alberta
Solomon
Islands
18.2
Idaho
Near co Jalisco,
MX
115.420
4.9
6.740
7.0
26.350
30.9
82.090
79.0
144.130
Good S-P
So. India
6.7
7.0
4.5
45.070
4.1
5.8
Turkmenestan
near Evansville,
IN
2.630
29.040
4.2
5.6
Kodiak Is. Reg.
New Ireland,
PNG
New Ireland,
PNG
New Ireland,
PNG
92.940
3.7
7.7
Lk Tanganyika
Windward Is.
Vanuatu Is.
6.0
Good S
Banda Sea
144.400
5.6
Good S
Long Surf wave
train
Coast Equador
112.100
5.8
6.5
Banda Sea
Michoacan,
Mex.
New Madrid
reg.
Int. depth,
P,pP,PP,S
Banda Sea
36.280
5.9
7.9
26.5
132.650
6.1
7.1
So. Sumatera
98.660
6.5
10/02/00
Salawesi
66.480
6.3
Comments
Quebec
132.060
6.0
7.1
8.610
Location
Arkansas
Jalisco, Mexico
Kuriles
Jawa,
Dist from PP
The AS-1 Seismograph – Operation…
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Indonesia
06/03/01
2:41:57
-29.666
-178.633
178
6.8
7.1
06/14/00
19:48:48
51.160
-179.828
18
6.0
06/18/01
19:56:56
-24.291
-69.173
89
5.5
5.8
06/19/01
9:32:25
-22.739
-67.877
147
5.5
6.1
06/23/01
20:33:14
-16.265
-73.641
33
6.7
06/24/01
1:22:53
-17.585
-71.958
33
5.4
06/26/01
4:18:31
-17.745
-71.649
24
6.2
06/26/01
14:05:07
61.340
-140.070
10
5.8
5.8
06/29/01
18:35:52
-19.522
-66.254
274
5.7
6.1
07/07/01
9:38:44
-17.543
-72.077
33
6.6
07/19/01
18:00:40
57.203
-151.036
33
5.9
07/24/01
5:00:09
-19.448
-69.255
33
5.7
07/26/01
0:21:37
39.059
24.244
10
6.0
07/28/01
7:32:43
59.025
-155.116
131
08/02/01
23:41:06
56.260
163.790
08/21/01
6:52:06
-36.813
08/25/01
2:02:03
7.633
08/28/01
6:56:09
09/04/01
09/05/01
6.3
8.2
109.770
6.5
6.2
5.9
8.4
6.5
6.8
7.3
61.490
66.480
?
5.5
?
6.3
65.300
7.7
57.740
5.5
59.370
6.2
59.600
64.1
6.0
38.130
42.6
6.1
62.670
61.800
N. Chile
6.5
5.6
59.310
6.2
6.3
5.9
6.6
7.0
6.1
5.7
5.7
6.6
6.1
14
5.9
6.2
6.3
5.7
-179.575
33
6.4
7.1
7.2
-82.766
25
5.9
5.7
6.1
5.9
32.870
-21.722
-70.108
66
5.8
5.9
6.2
12:45:53
37.143
-104.650
5
4.0
10:52:08
37.143
-104.618
5
4.5
09/07/01
2:45:59
-13.166
97.297
10
6.2
09/11/01
9:13:26
14.995
-91.571
161
5.0
6.4
S. Alaska
Near E co
Kamchatka
E of N Is. New
Zealand
33.6
63.790
S. of Panama
Near co of N
Chile
4.1
14.230
So. Colorado
4.5
14.210
So. Colorado
S. Indian
Ocean
66.720
7.0
114.460
152.580
25.680
09/14/01
4:45:12
48.904
-128.317
10
5.5
5.8
6.0
5.5
30.330
09/16/01
23:20:09
48.540
-128.600
10
5.1
5.4
5.6
5.4
30.510
10/12/01
5:02:34
52.850
-132.110
10
5.5
5.7
5.7
5.6
10/12/01
15:02:16
12.590
144.940
37
6.6
7.0
7.0
34.1
32.880
6.9
108.690
10/14/01
1:10:45
-8.590
144.660
68
5.9
4.9
5.9
10/17/01
11:29:09
19.313
-64.912
33
5.3
5.6
6.0
144.660
10/19/01
3:28:41
-4.043
123.933
10
6.3
7.3
7.5
10/21/01
0:29:24
-36.992
179.030
33
10/30/01
3:24:28
24.066
-109.038
10
5.3
4.9
5.5
5.4
24.740
11/13/01
9:47:36
22.264
-106.949
33
5.5
5.8
6.1
5.5
24.830
11/14/01
9:26:10
35.945
90.535
10
6.1
8.0
7.7
5.5
28.260
14:32:32
15.560
-93.090
85
5.7
6.3
5.9
25.370
13:01:53
39.530
141.067
122
6.1
6.5
6.4
89.180
Honshu, Japan
12/12/01
14:02:35
-42.813
124.688
10
6.5
6.7
7.0
156.340
12/23/01
22:52:54
-9.613
159.530
16
6.2
7.0
6.7
6.9
114.090
01/02/02
17:22:48
-17.600
167.856
10
6.3
7.5
7.1
7.1
112.680
4.9
S of Australia
Solomon
Islands
Vanuatu
Islands
Off E co United
States
Chiapas,
Mexico
Vera Cruz, MX,
P,pP,S
Chiapas,
Mexico
8:26:53
28.279
-69.566
10
5.7
23:09:52
15.502
-93.133
80
5.8
115.500
7.5
?
103.960
5.4
5.7
18.720
6.4
5.8
25.430
01/30/02
8:42:03
18.194
-95.908
108
5.6
5.9
5.7
23.490
02/14/02
23:23:13
14.975
-92.470
74
5.3
5.8
5.7
25.930
02/22/02
19:32:42
32.375
-115.352
10
5.3
5.7
5.4
03/03/02
12:08:23
36.543
70.424
256
6.6
03/05/02
21:16:10
6.171
124.284
31
6.3
03/27/02
11:18:04
30.138
-114.070
10
4.7
03/28/02
4:56:21
-21.590
-68.170
122
6.2
5.5
7.2
30.3
N. Baja
Hindu Kush,
Afganistan
Mindanao,
Philippines
Gulf of
California
Chile-Bolivia
border region
100.610
7.2
6.5
19.0
24.200
7.3
6.9
125.470
5.1
24.360
6.4
64.130
7.1
P,PP,S,SS
Virgin Islands
12/02/01
01/16/02
6.7
35.3
11/28/01
01/12/02
134.350
Good complete
seismogram
Guatemala
Off coast
Vancouver Is.
Off coast
Vancouver Is.
Queen
Charlotte
Islands
S. of Marianas
Islands
Jawa,
Indonesia
Banda Sea
Near E co N Is
New Zeal
Gulf of
California
Near co Cent
Mexico
Qinghai Prov.,
China
Near co
Chiapas,
Mexico
6.8
6.8
Dist from PP
Aegean Sea
43.9
6.2
?
68.3
78.980
45.620
5.7
N. Chile
Chile-Bolivia
border region
Near coast of
Peru
Near coast of
Peru
Near coast of
Peru
S. Yukon
territory
43.680
7.6
6.0
6.8
Kermadec Is.
Andreanof Is.,
Aleutians
S. Bolivia
Near coast of
Peru
Kodiak Island
area
5.9
5.8
107.0
03/31/02
6:52:50
24.410
122.210
33
6.4
7.2
7.1
04/01/02
19:59:32
-29.490
-71.070
69
6.2
5.7
6.4
6.4
110.030
71.110
71.0
04/18/02
5:02:47
16.950
-100.820
33
5.3
6.0
6.3
5.6
26.300
28.9
Taiwan
Near co.
Central Chile
Near co.
Guerrero, MX
P and pP phases
PP,SS, Good 20s
surf waves
Good S-P
The AS-1 Seismograph – Operation…
6.2
Page 2 of 18
04/18/02
16:08:36
-27.350
-70.050
62
6.3
6.6
6.6
69.240
04/18/02
17:57:23
16.800
-101.020
33
4.9
4.9
5.4
26.540
30.3
04/20/02
10:50:45
44.510
-73.660
5
5.1
04/26/02
16:06:07
13.114
144.562
85
6.6
5.1
5.7
5.7
10.590
9.9
7.0
7.1
05/17/02
10:40:10
48.100
-27.829
10
5.6
5.4
5.7
5.6
42.060
05/21/02
6:03:00
17.780
-81.916
10
5.3
5.0
5.7
5.5
22.990
05/25/02
5:36:31
53.930
-161.270
33
5.4
6.0
6.0
5.5
05/28/02
4:04:22
-28.890
-66.570
21
6.1
5.7
6.0
6.3
06/05/02
12:45:16
35.347
-36.17
10
5.5
5.1
5.7
06/05/02
20:17:38
52.92
-74.42
18
06/07/02
17:00:51
16.091
-96.637
33
5.5
5.0
5.6
06/13/02
1:27:18
-47.776
99.561
10
5.4
6.6
6.6
2:46:13
8.740
-84.026
33
5.4
6.2
6.4
06/17/02
21:26:23
-12.581
166.349
33
6.0
6.6
6.7
06/18/02
13:56:22
-30.754
-70.964
53
6.0
06/18/02
17:37:15
37.985
-87.778
5
06/22/02
2:58:21
35.616
49.050
10
6.3
6.4
6.5
06/27/02
5:50:33
-6.990
103.790
10
6.1
6.9
6.6
6.6
50.010
48.0
57.0
4.2
N. Quebec
25.740
2.8
Oaxaca, MX
SE Indian
Ridge
Off Coast of
Costa Rica
Santa Cruz
Islands Reg.
Chile-Argentina
bor. Reg.
near Evansville,
IN
Western Iran
SW of Sumatra,
Indo.
E Russia -NE
China Bor.
Off coast of
Oregon
31.710
6.5
110.780
6.3
72.400
5.0
5.3
6.3
2.590
94.110
6.8
145.310
06/28/02
17:19:30
43.770
130.720
564
6.8
7.3
7.2
89.540
07/09/02
18:40:35
43.560
-127.227
10
5.6
5.5
6.0
5.7
29.930
31.7
07/31/02
0:16:45
7.929
-82.793
10
6.0
6.4
6.5
6.1
32.620
35.3
08/14/02
13:57:56
14.190
146.130
65
6.1
09/06/02
1:21:27
38.371
13.698
10
5.8
5.6
5.9
09/08/02
18:44:23
-3.271
142.855
13
6.4
7.8
7.3
09/24/02
3:57:22
-31.429
-68.960
120
6.3
6.4
6.7
73.450
72.7
10/03/02
16:08:28
23.231
-108.495
10
5.4
6.2
6.4
6.1
25.050
27.8
10/11/02
14:41:24
15.555
-95.603
33
5.2
5.0
5.7
25.970
10/12/02
20:09:11
-8.270
-71.695
533
6.5
6.9
6.9
50.490
10/23/02
11:04:20
63.576
-148.088
10
6.0
6.7
6.7
6.0
6.7
42.040
39.8
11/02/02
1:26:11
2.971
96.156
33
6.1
7.7
7.7
7.3
136.670
11/03/02
1:49:29
51.594
-130.627
16
5.3
5.3
6.1
6.1
11/03/02
3:37:43
38.876
141.917
49
11/03/02
20:41:57
42.815
-98.908
5
11/03/02
22:12:41
63.520
-147.530
5
11/11/02
23:39:29
32.366
-80.072
5
6.4
6.0
7.3
6.9
8.6
7.9
6.9
4.2
29.2
Sicily, Italy
N. coast New
Guinea
San Juan Prov.,
Argentina
150 km ENE
Cabo, MX
Offshore
Oaxaca, MX
44.2
W Brazil
Deep focus
Central Alaska
Northern
Sumatra
Queen
Charlotte
Islands
N Honshu,
Japan
Denali Fault
30.9
9.300
41.780
4.3
S. of Panama
73.160
89.310
4.4
Right lateral strike
slip
Mariana Islands
31.880
6.0
4.3
S-P
106.710
121.930
5.4
Aleutians
15.060
171.370
5.6
PP-P
Argentina
N. Mid-Atlantic
ridge
39.890
5.2
Plattsburgh, NY
Near Guam,
Mariana Is.
No. Mid
Atlanatic Ridge
not shallow, weak
surf. Waves
Also 4.9 event 3
min. later
Good S-P, Large
Lg arrival
N. of Honduras
71.510
5.8
6.6
4.4
108.520
5.5
4.5
06/16/02
5.7
6.9
Near co. N.
Chile
Near co.
Guerrero, MX
9.780
N Nebraska
45.3
Central Alaska
Near
Charleston, SC
Denali Fault
The AS-1 Seismograph – Installation…
Page 16 of 18
2. Comparing seismograms. Seismograms recorded on the AS-1 seismograph can be
compared with records from other stations. Seismograms recorded by the AS-1
seismograph can be printed from the AmaSeis software for comparison with other
seismograms. Because most seismic data available on the Internet are recorded by either
broadband or long period seismometers, it is best to filter the AS-1 record for long periods
(use 0.0001 and 0.1 Hz cutoffs). Seismograms for significant events recorded by the
IRIS/USGS Global Seismograph Network (GSN, IRIS/DMC WILBER data retrieval tool;
http://www.iris.washington.edu/; select the WILBER tool from the Quick Links menu on the
left side of the screen) or from Princeton Earth Physics Project (PEPP;
http://lasker.princeton.edu/index.shtml) stations can be viewed at the Internet locations
given here. One can also download data from these sites to your own computer and view
and print them with the AmaSeis software. It is recommended that you download one
seismogram at a time. For the IRIS/DMC/WILBER data, select an event and then a station
of interest (you can view the seismogram by clicking on the station name). Select a
seismogram to be downloaded by clicking on the box next to the station name, click on the
LHZ component (for most appropriate comparison to the filtered AS-1 record; other
components may be selected for other purposes such as identifying S wave arrival times on
horizontal components) and select SAC binary individual files for the download format.
The file will usually be available in about a minute or so and you will be informed when it is
available. Clicking on the URL provided by WILBER and on the file name will download
the seismogram data to your computer (download to the AmaSeis folder or to a download
folder and then move it to the AmaSeis folder). Now you can view and print the
seismogram from a GSN station using AmaSeis by opening the file. The file will have a
.sac file extension. You can view seismograms from the PEPP network by clicking on the
station names listed for each event. Make a data request by typing the station name into the
box provided, checking the BHZ component box and submitting a request. The data will be
downloaded to your computer and will have a .set file extension. Place in the AmaSeis
folder. You can now open, view and print the PEPP seismogram from the AmaSeis
software. By selecting GSN or PEPP stations for viewing or downloading that are
approximately the same distance from the epicenter as your AS-1 seismograph, you can
easily compare your record to standard seismograph records. Additionally, by selecting
closer or more distant stations, you can investigate the effect of distance of propagation on
the seismogram characteristics and illustrate the variation of seismic waves at different
distances from the earthquake.
3. Maintain a map of locations of events recorded by your station. Place a copy of the map
This Dynamic Planet (Simkin et al., This Dynamic Planet, map, USGS, 1:30,000,000 scale
($7 + $5 shipping), 1994, also at: http://pubs.usgs.gov/pdf/planet.html; 1-888-ASK-USGS)
on the wall in the classroom. Whenever there is an earthquake that you record on the AS-1
seismograph and are able to determine the magnitude, plot the location of the earthquake on
the map using a colored, self-adhesive dot. Next to the dot, place a small label (selfadhesive address labels work well) with the date, time and magnitude information on it. If
you continue this process for several months you will have a useful illustration of the
seismograph records that you have interpreted and the comparison of the locations with the
historical epicenters on the This Dynamic Planet map will help emphasize the relationship of
The AS-1 Seismograph – Installation…
Page 17 of 18
active earthquake zones to plate tectonics. Additionally, on could tape a small copy of the
AS-1 seismogram next to each event to further enhance the display (Figure 12). Significant
differences between the various seismograms will be visible because of the different
epicentral distances, magnitudes and depths of focus of the earthquakes. The earthquake
map will become a significant focal point for the classroom for students, teachers and
parents.
Figure 12. Display of seismograms recorded on an AS-1 seismograph (orange triangle shows station
location) from earthquakes (epicenters are shown by red dots) at various locations around the world. The
base map is the “This Dynamic Planet” map.
4. Upload/Download AS-1 data. You can upload your AS-1 seismic data (SAC files) to the
SpiNet site (http://www.scieds.com/spinet/) to share your seismograms of interest with other AS-1
station operators and other scientists and educators. To download seismograms from other AS-1
The AS-1 Seismograph – Installation…
Page 18 of 18
stations (for comparison or S-P earthquake location method application), go to:
http://www.scieds.com/spinet/recent.html; click on the desired seismogram; a download window
will be displayed; open the seismogram (which is stored as a SAC file and has a name such as
0211032212WLIN.sac, where the digits are: 2-digit year, 2-digit month, 2-digit day, 2-digit hour, 2digit minutes [arrival time] followed by the station code) using AmaSeis.
References:
Bolt, B.A., Earthquakes and Geological Discovery, Scientific American Library, W.H. Freeman,
New York, 229 pp., 1993.
Bolt, B.A., Earthquakes, (4th edition), W.H. Freeman & Company, New York, 364 pp., 1999.
Return to Braile’s Earth Science Education Activities page
Related Pages:
The AS-1 Seismograph – Installation and Calibration
The AS-1 Seismograph –Magnitude Determination