www.eas.purdue.edu/~braile
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| braile@purdue.edu
| Purdue EAS | IRIS | Seismic Monitor | Earthquakes – USGS |
| USGS tt calculator | USGS LISS | SpiNet | AS-1 MagCalc |
Alan Jones’ Site
| SAGE | Workshops |
www.eas.purdue.edu/~braile

Seismic/Eruption includes up-to-date earthquake and volcanic eruption catalogs and allows the user to display earthquake and volcanic eruption activity in “speeded up real time” on global, regional or local maps that also show the topography of the area in a shaded relief map image. Seismic/Eruption is an interactive program that volcanic eruption data and produce effective displays to illustrate seismicity and volcano patterns.
Seismic/Eruption Features:
1.
View earthquakes and eruptions, select range of dates, magnitudes, color code depth
2.
Use standard views provided with program to explore areas and tectonic settings
3.
Update earthquake locations from Internet
4.
“Make Your Own Map” option
5.
Display/add shaded relief topography
6.
Make cross-section diagrams and 3-D views
7.
Select earthquake data for statistical analysis
8.
Save views, export images, make posters
Some basic activities:
1.
Exploring the Standard Views
Use the standard views provided with Seismic/Eruption to view seismicity and volcanic activity of selected locations. Start with the world view and then the Pacific Ocean region. Change the playback speed and switch earthquakes and eruptions on and off in order to see one type of activity at a time. Note the depth legend and counters at the right side of the screen. Also note that one can choose a magnitude or eruption magnitude cutoff. Continue exploring the standard views by focusing in on an area of interest to you such as Japan, Indonesia, South America, Alaska, California, etc. Note that for some of these areas the earthquake files are adjusted for a relatively short time period (this can be controlled in the Control menu) sometimes to focus on a mainshock/aftershock sequence and that some cross section views are available.
Note also that topographic relief maps are provided for the views. For selected areas, view earthquakes and eruptions separately.
2.
Make Your Own Map
From one of the standard views one can zoom in on an area and make your own map. To do this, open the
Map menu and select Make your own map. Follow the directions on the screen. To update the topographic relief data base (for the conterminous US where 30 arc second topographic data are available), select
Shaded Terrain/Digital Elevation Models from the Map menu, then click on the TOPO30 file. Click on OK and then select Redraw from the Map menu. You can change display options for your map view and observe earthquakes or eruptions in your selected area. More detailed instructions and suggestions: a.
Open the view with that contains your area of interest (for example, for a state in the US, open the
United States view). b.
Select from the Map menu, Make Your Own Map.
c.
Click OK.
d.
With the mouse, click and hold (drag) from the upper left hand corner of the area of interest to the lower right hand corner.
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e.
Click Yes ; map appears on screen. f.
To get a better topographic background (shaded relief map) or to add topography if the screen
(background) is blank, you can select an elevation file ( etopo5 or topo30 ) if these files have been added to the TOPO folder within the SEISVOLE folder (see SeisVolE Teaching Module 1
, “Downloading and Installing SeisVolE”), otherwise, go to g.
1) Select Shaded Terrain , Digital Elevation Models from the Map menu.
2) A dialog box will appear; in the upper left hand corner click on:
World 5-minute DEM (ETOPO5) , if the area is outside the US, or,
USA 30-second DEM (TOPO30) , if the area is in the conterminous US and you have added the topo30 elevation file.
3) In the lower left hand corner of the dialog box, be sure that the boxes to the right of ETOPO5 and TOPO30 look like the following:
ETOPO5 \seisvole\topo\etopo5.
TOPO30 \seisvole\topo\topo30. g.
Click OK.
h.
Select Redraw from the Map menu (move the mouse quickly away from the map area after selecting
Redraw to avoid generating a blank area behind the mouse position as the new map is drawn). i.
Adjust buttons at bottom of screen (magnitude cutoff, selecting earthquakes or volcanoes, etc.) if necessary. j.
Adjust menu items at top of screen (set dates, magnitude/depth scale, etc.) if necessary. k.
Add title and city locations (select Annotations from the Map menu) if desired. l.
Click Repeat to start earthquake sequence. m.
To save the view, select Save View As from File menu.
IDEAS: n.
To save the image (for printing or exporting to another document), select Make Bitmap from Options menu. Save the Bitmap file in the SEISVOLE folder or other location. This file can be imported into an MS Word document or an image processing program such as Adobe Photo Deluxe .
Comparison of the number of earthquakes between states; the largest earthquake in each state; an active volcano in the state (where is it?), if not, where is the closest?; frequency/magnitude for map; compare number of earthquakes in regions of U.S. (NW vs. SE) report.
Assignment possibilities:
Choose your own state. Make a natural hazards brochure or poster. Also oral report and or written
3.
Making a Cross Section
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a.
Select a view or make your own map. b.
Run the map (view earthquakes and/or eruptions through time); note the depth extent of the hypocenters; set Magnitude/Depth Scale in the Earthquakes menu (for subduction zones, normally, set the maximum depth to 500 or 750 km). c.
Select the Set Up Cross-Section View from the Contro l menu. d.
Click on the map; a red profile will appear on the map and a rectangular area with data boxes and buttons will appear near the bottom of the screen. e.
Adjust Azimuth, profile Length, and profile Width (hypocenters within the white rectangular area will be projected onto the profile); use the arrows to adjust the azimuth, when you stop clicking on the arrows, the red profile will rotate on the map to the new orientation; highlight the Length and Width values and type in new values; click Redraw to view the profile; adjust azimuth, length and width until satisfied; click on the red profile, hold down the left mouse button and drag the profile into the desired position; click OK ; see example below:
Profile (red line) and area (white rectangle) of epicenters to be projected onto the profile for a cross-section view.
Profile azimuth, profile length and profile width values are given in the data boxes at bottom left. The area/view is the Kuriles and Kamchatka standard view. Earthquake depths are color-coded according to the depth scale in the upper right. f.
In the Control menu, click on MapView/3D/Cross-Section and then on Cross-Section View.
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g.
Run the map (view earthquakes and/or eruptions through time); an example is shown below:
Cross-section view showing hypocenters corresponding to the epicenters shown in the white rectangle in the view shown above. Hypocenters are color-coded according to the depth scale in the upper right. The vertical scale is depth in km. The horizontal scale is distance along the profile in km. The profile is oriented from NW (on the left) to SE (on the right). h.
To save the view select Save View As from the File menu. i.
To save the image to print or export to another document, select Make Bitmap from the Options menu. Save the Bitmap file in the SEISVOLE folder or other location. This file can be imported into an MS Word document or an image processing program such as Adobe Photo Deluxe .
4.
Creating Frequency-Magnitude Plots a.
Select a standard view or make your own map. b.
Set Dates (in the Control menu), for example, for 41 years of data, set dates to Jan. 1, 1960 to Dec. 31,
2000. c.
Select earthquakes or eruptions (buttons at bottom of screen). d.
Set magnitude cutoff (for earthquakes or eruptions); start with a small magnitude cutoff, for eruptions, begin with 1; for earthquakes, begin with 3 for California, 4 for the conterminous US, and 5 for the rest of the world.
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e.
Run the view (click on Repeat if needed), write down the total number of events within the area (for magnitudes greater than or equal to the cutoff magnitude) from the counter to the right of the map display. f.
Increment the magnitude cutoff and repeat (begin at e.). g.
Make a data table and a graph of the data (see examples below; see Excel instructions).
Magnitude Number of events
(in 41 Years)
5+
6+
7+
3667
351
73
8+ 6
*IDEAS: Use 0.5 magnitude interval; suggest 1 yr/sec speed step interval; use step to look at individual events; good idea to plot by hand first, then use excel; suggest linear scale then use logarithmic scale in graph.
*QUESTIONS:

Suggest that students, in groups of four, each make a plot of a different region and compare the resulting plots.
 Ask students, “How can this information be used to help forecast future events?”
“How is this information useful for hazard assessment?”
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4000
3500
3000
2500
2000
3667
1500
1000
500 351
73
6
0
5+ 6+ 7+ 8+
Magnitude
See Teaching Module
6. “ Instructions for Producing Graphs Using Excel” for more information on creating data tables (spread sheets) and graphs using Excel . The graph may also be plotted on a logarithmic (log) scale as shown below:
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10000
1000
100
10
1
4 5 6 7
Magnitude, M
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The Seismic Waves program is a simulation of wave propagation through the Earth. Various phases (arrivals) for different wave types are viewed in speeded up time resulting in a “video” of how waves travel through the Earth.
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Figure 29. Partial screen views of the Seismic Waves computer program. The upper image shows seismic wavefronts traveling through the Earth's interior five minutes after the earthquake. The lower image shows the wavefronts 7 minutes after the earthquake. P waves are shown in red; S waves are shown in blue; and Surface waves are shown in yellow. Three and four letter labels on the Earth's surface show relative locations of seismograph stations that recorded seismic waves corresponding to the wavefront representations in the Seismic
Waves program.
Seismic Waves uses a wave front approach to illustrating seismic wave propagation. This view has many advantages and is an accurate representation of how waves propagate. However, sometimes it is useful to consider seismic ray paths that follow the direction of travel of a specific point on the wave front from source to receiver.
For example, ray paths are sued on the IRIS Exploring the Earth Using Seismology poster:
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A comparison of wave front and ray path views for a simple Earth model is shown below:
Figure 6. Raypaths and wavefronts for selected primary (compressional) wave phases which travel through the Earth. The travel times (in minutes) along the raypaths and the corresponding wavefronts (short dashed lines; lines or surface of equal travel time) are given by the small numbers adjacent to the wavefronts. The raypaths are perpendicular to the wavefronts and represent the direction that a specific point on the wavefront is propagating. The raypaths in this real Earth model are
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curved because the seismic wave velocity varies with depth. Note the strong refraction (bending) of the raypaths and wavefronts caused by the velocity change across the core-mantle boundary. The primary wave types (phases) illustrated in this diagram are:
P Raypaths for waves which travel through the mantle with a reltively direct path; 0

-103

distance range.
Pdiffracted Raypaths for waves which travel through the mantle and are diffracted at the core-mantle boundary by the reduced outer core velocity; 103

-150

distance range.
PKP
PKIKP
Raypaths for waves which travel through the mantle, are strongly refracted at the core-mantle boundary and travel through the outer core; 110

-187

distance range.
Raypaths for waves which travel through the mantle, the outer core and the inner core; 110

-180

PKiKP distance range.
Raypaths for waves that are reflected from the inner core. In more recent models of the Earth's interior, the PKiKP arrivals are observed for distances less than about 120

.
Explore the Seismic Waves program and view wave propagation through the Earth for one or more sources. Note the different views that are available and the related seismograms which show the arrivals in speeded up time.
You can select different views and control the playback and use pause and restart to focus on a wave propagation feature of interest such as the P wave reflection at the core/mantle boundary or the S to P conversion of energy at the same boundary. Some suggested questions and explorations for students are given below:
Obtain the Seismic Waves computer program and demonstrate to the students or provide the students with the opportunity to run the program. Next, with the program available on a monitor, start waves propagating (pause or restart as necessary) for one of the earthquakes and have the students watch the wavefront diagram (interior of
Earth; it is convenient to set the display to view only the Earth cross section view; use the "Options" menu and
"Select View …" to choose the cross section view) and have them answer the following questions. What are the approximate shapes of the initial (in the upper mantle near the source) P and S wavefronts? Why are they shaped that way? From the P and S wavefronts, estimate the relative velocity of the S wave as compared to the P wave
(for example, how much longer does it take for the S wave to arrive at a station or to travel from the source to the core-mantle boundary as compared to the P wave)? How long does it take for the P wave to travel directly through the Earth to the opposite side of the Earth from the source? This distance (the diameter of the Earth) is about
12,742 km. From these measurements, what is the approximate average velocity for P waves in the Earth (in km/s)? Explain the new wavefronts that are generated when the P or S wave hits the core-mantle boundary. Why is there no S wave that travels directly through the Earth to the other side? Can there be S waves in the inner core
(the program may not be of much help here except to visualize wavefronts that propagate in the Earth's core because no S wave phases from the inner core are displayed; not all seismic phases or raypaths are illustrated by the program)? How could S waves be generated so that they would travel through the inner core? Open the whole
Earth view (surface of Earth with oceans and continents is visible). How are the patterns of the wavefronts that you see propagating and expanding from the source similar to the water waves in the wave tank experiment (or generated by a pebble dropped into a mud puddle or a pond)? How are they different?
For detailed information, see the online materials on L. Braile’s web page and related links. Below are some results and examples of earthquake monitoring using the AS-1 Seismometer and the AmaSeis software.
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5 minutes
January 22, 2003, M7.8, Colima, Mexico earthquake recorded on an AS-1 seismograph and AmaSeis software at
West Lafayette, IN. Distance = 26.01 degrees. Seismogram was filtered from 0.001 – 0.1 Hz.
Maintaining a catalog of recorded earthquakes is a convenient and educational exercise associated with educational seismograph operation. Data entries require observation and analysis of seismograms, retrieving information from the internet and performing simple calculations.
Continuous or short duration (several weeks or months) recording of earthquakes with an educational seismograph is an excellent component of an in-depth science experience that includes record keeping, mathematical calculations and opportunities for significant learning about earthquakes, seismology, plate tectonics and related
Earth science. Using the seismograph and recorded seismograms, students can “do science” using their own real data rather than just reading about or listening to descriptions of science. Monitoring earthquakes requires the useful exercises of maintaining an instrument, good record keeping (see example of a portion of an earthquake catalog above), retrieving additional information on the earthquake from the Internet, and making consistent observations of data. Over 3 years of experience with monitoring earthquakes with the AS-1 seismograph demonstrates that even in the relatively low seismicity Midwest or eastern North America, frequent (mostly teleseismic) earthquakes are recorded at relatively quiet sites. Visible earthquake seismograms are present every few days and an event that produces a seismogram that can be used for magnitude or distance calculations occurs, on the average, about once per week. The AmaSeis software (developed by Alan Jones for the AS-1 seismograph with support from IRIS) is easy to use and provides several useful features and tools for archiving, viewing and analyzing data. Exercises that use the recorded earthquake data include determining magnitude and epicenter to station distance. Although the AS-1 is a relatively simple and inexpensive seismograph, the results of these analyses are reasonably accurate (see examples below) thus validating the students’ efforts and increasing the interest in learning. Additional information about the AS-1 seismograph, AS-1 magnitude calculations and using the AS-1/AmaSeis seismograph in educational seismology is contained in the listed website.
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Using the AmaSeis travel time curve tool to determine the epicenter-to-station distance from the S-P arrival times. January 22, 2003,
M7.8, Colima, Mexico earthquake recorded on an AS-1 seismograph and AmaSeis software at West Lafayette, IN; Distance = 26.01 degrees.
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Comparing actual and AS-1/AmaSeis S-P calculated distances. N = 55; Standard Deviation = 2.83 degrees (September,
2003).
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Comparing actual and AS-1/AmaSeis magnitudes (September, 2003). The AS-1 magnitude calculations result in accurate magnitude determinations. Standard deviations of the differences between AS-1 (single station) and USGS (average of many stations) magnitudes are similar to other (standard seismograph) single station uncertainties.
MS Magnitudes: N = 64; Standard Deviation = 0.26 magnitude units. mb Magnitudes: N = 111; Standard Deviation = 0.25 magnitude units.
mbLg Magnitudes: N = 16; Standard Deviation = 0.26 magnitude units.
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