South American focal mechanisms, oblique 3D view from southeast. Click for larger size. Global CMT Project (www.globalcmt.org) data. |
The GEON Integrated Data Viewer Contents
INTRO
Introducing the GEON IDV
INSTALL
Download & Run the GEON IDV
LEARN
... How to Use the GEON IDV
... Bundles
YOUR DATA Data Formats for the IDV |
Seismic Focal Mechanism Plots and Data Sources in the GEON IDV
View from side of 500 Tonga region focal mechanisms and 2442 hypocenters.
(data courtesy GMT Project and IRIS DMC)
The GEON IDV can display earthquake focal mechanism parameters four different ways. The display symbols are the focal mechanism "beachball" (lower half of sphere), full beachball (sphere) for earthquakes below seismic receivers, the P and T axes, and the slip direction.
To get focal mechanism plots and the P and T axes, you must install a Geon IDV plugin made available on or after 25-11-2008. See part 2 in Install the GEON IDV. First un-install any older Geon IDV plugin. If you aren't sure which plugin you have, un-install the plugin you have, and install the new plugin.
The IDV is fully interactive, with true 3D displays. You can rotate, zoom, and pan the display, scale plot symbols to any size, change map projections, and include many types of data in one display. The goal of the IDV is to be a powerful 3D exploration tool for complex 3D Earth data.
GEON IDV 3D oblique view from the south, of five focal mechanisms, plotted as the beachball (lower half), the P and T axes (white and blue) and the slip direction (green).
From top to bottom, a low angle reverse, a reverse fault, a high angle reverse, a normal fault, and a pure strike slip fault.
Data is synthetic.
Click for larger size.
Full beachball plot (sphere); oblique view from south, of the same sources.
P and T axes (white and blue); slip directions (green); oblique view, of the same sources.
You can plot a map view of focal mechanisms:
(data courtesy of Francis Wu)
Or rotate into a 3D oblique view:
Or make a transect box in the map view, to see a vertical slice of the Earth:
You can get a numerical data readout when you click on a focal mechanism symbol in the IDV display:
Focal Mechanism Data File Format for the GEON IDV
This is "point data," a collection of observed values at randomly located positions.
See
Point Data in Text Format (csv files).
CSV files are simple ASCII files with one earthquake per line, with comma separated values.
Each row is for for one earthquake, and includes hypocentral location, time, magnitude, Mo, and a comment, as well as the three fault plane values of strike, dip and rake.
Note that depths ("Altitude") are negative downwards below the surface.
For more details about IDV ASCII csv file format, see
Text (ASCII) Point Data Format.
Make your own data files in the same format, keeping the two header lines unchanged.
Use the same format for the data rows.
The magnitude, comment, and Mo data items are optional for focal mechanism plots, but when they are
included in a data file you can also plot the hypocenters as points colored or sized by magnitude,
and label the plot with the comment.
The IDV can plot all times at once, or show each time in one display,
do customary time animation, and also do accumulating
time animation showing all points after a start time, for example, aftershocks appearing
after an earthquake.
You can use this file to make test focal mechanism displays in the GEON IDV.
Just "copy link location" for the
sample IDV focal mechanism file, and see the instructions below in "Making Displays."
Note that the IDV can read data from files on remote servers without copying the file.
Standard Focal Mechanism Data Sources for the GEON IDV
Global CMT Project Focal Mechanism Data
GMT's original NDK format files were converted by UNAVCO to IDV "csv" files,
and subsetted for selected regions. With these data files you can plot focal mechanisms, hypocenters, hypocenters
colored by magnitude, and hypocenters colored by depth, in the GEON IDV.
Selected Global CMT Project data in files for the IDV; enter a URL into the GEON IDV's Data Chooser URLs window:
data: Europe to longitude 22 (206 earthquakes)
data: all GMT earthquakes in the U.S. lower 48 states (202 events)
data: GMT earthquakes East Asia (884 earthquakes, 17 to 43 latitude, 100 to 137 longitude)
Click for GEON IDV display of that data
data: 500 South American earthquakes
data: 762 quakes in Tibet region; 25.0 to 45.0 latitude, 65.0 to 110.0 longtitude, 0 to 800 km depth
data: 500 quakes near Tonga, 30 to 20 S, 170 to 180 West, to 700 km depth
data: 1807 quakes near Japan, 25 to 45 north latitude, 125 to 150 east longtitude, all depths
Data Source Authors: Göran Ekstom, Adam Dziewonski, Meredith Nettles
Original Data location online: see
Data Source Publication: see
http://www.seismology.harvard.edu/projects/CMT/cmt_pubs.html
Data Source format: NDK
Format conversion for IDV use: converted to IDV .csv format by UNAVCO
First get the NDK file of Global CMT Project data, from the CMT catalog at http://www.globalcmt.org/CMTfiles.html, called jan76_dec05.ndk.
That file has all events 1976-2005; more recent data may be found there, by month.
Movies of GEON IDV Displays of GMT focal mechanism data
Quicktime movie of Tonga focal mechanisms (Global CMT Project catalog data)
Animated gif movie of Tonga focal mechanism beachballs (Global CMT Project catalog data)
Animated gif movie of 2442 Tonga focal mechanism T and P axes (T blue; Global CMT Project catalog data)
European-Mediterranean Regional Centroid Moment Tensors
not yet converted to .csv format used by the GEON IDV
The Northern California Earthquake Data Center (NCEDC) moment tensor Catalog
for events in northern and central California and notable earthquakes in the western United States.
not yet converted to .csv format used by the GEON IDV
USGS, 5796 focal mechanisms, 1980 to 31 Oct 2007 (ASCII, 852 kB)
not yet converted to .csv format used by the GEON IDV
Making Displays
This is not a complete description of how to use the IDV.
See
the GEON IDV How To
and
Unidata's Integrated Data Viewer guide.
First set the display to a
vertical scale
suitable for your data.
Then set a
map projection (map area)
suitable for your data, or just check the box for
the the menu choice Projections->Auto-set projection.
Connect to a data source
with the Dashboard window, Data Choosers tab:
For data sources with an HTTP server (with a URL), use section "URLs."
If your data format is an ASCII .csv file like the data files listed above,
use Data Type choice "I'm feeling lucky" which means the IDV will recognize the point
data type from the file name extension.
For local files choose the "Files" section, and navigate to the file on your local disk,
After you have the data file indicated, click the "Add source" button.
After you
connect to the data source, the Dashboard shows the Field Selector for that data:
To make a display for a Field (parameter) type,
first click on a display
type in the Displays panel of the same window, and then click on the "Create Display" button.
Focal mechanism data has Field type "Point Data,"
and the Displays panel shows the choice
"Point Data Plot" and "Point Data List." Click on "Point Data Plot", then click on
the "Create Display" button.
When a display is made the Dashboard shows the "display control" panel for that display:
One plot symbol is on the map, for the first time.
You may be asked if you really want to display a large number of data points:
In the display control, click on the Times tab:
Click on the Multiple
button; otherwise there will be many displays, one for each data time. Like 500 displays!
In the Layout tab,
In the "display control" panel for the display, note the pull down
menu called Layout Model which has a list of the plot symbols available for all kinds of point
data.
At first a Point Data Plot display will use plot symbols called "Locations 3D Cross,"
or whatever happens to be first in the "Layout Model" list.
To use another plot symbol,
choose one from the pull-down menu, such as
Focal Mechanism beachball, lower half.
Conventional focal mechanism symbols in publications usually are overhead map views
showing the lower half of the focal mechanism "beachball."
Since the IDV is a true 3D system, you can see
data from any viewpoint.
You may also plot the "Focal mechanism beachball, full sphere," P and T axes, or the slip direction.
You can make all three plots for
each focal mechanism at the same time.
After you see the plotted data you may wish to enlarge the symbol with the Scale entry box in
the display control in the Dashboard window.
You also can thicken lines in plot symbols with the Line Width entry box.
Beachballs often look better with a Scale of 2 or 4 and a line with from 2 to 3.
To zoom, pan, and rotate see
Zoom, pan and rotate.
To make a transect display, see
Transect View.
For use of point data symbols,
read more about
Point data plots
and
Working with the Point data Plot Symbols using "Layouts Models"
and
Color a Point Data plot symbol using Layout Models
(data courtesy of Francis Wu)
(data courtesy of Francis Wu)
Here is a file of six focal mechanisms with data from the USGS:
sample IDV focal mechanism file
A GEON IDV display with these focal mechanisms is shown above.
data: Europe, -22 to 40 longitude, 35 to 70 latitude(449 earthquakes)
Click for GEON IDV display of that data
Click for GEON IDV display of that data
Click for GEON IDV map view of data
Click for GEON IDV display of that data with hypocenters
bundle file for that display
Click for GEON IDV display of that data with focal mechnanisms
bundle file for that display
"CMT catalog web search" at http://www.globalcmt.org/CMTsearch.html
CMT catalog and Quick CMT ASCII files at http://www.globalcmt.org/CMTfiles.html
A Python program to convert the Global CMT Project NDK-format data to GEON IDV file is
here. Read the header of the
program to see how to use it. You need the Python interpreter for your computer;
on Linux type "which python" to see if you have it. Python is online at www.python.org.
This program only extracts the hypocentral location, time, mb, Ms, strike, dip, and rake.
It can be modiifed to extract additional moment tensor values.
Generally the IDV can show 500 to 1000 focal mechanisms with reasonable response;
the more the sources the slower the response.
check OFF the Declutter box,
or slide the Density slider towards High, to see more events. Declutter off means show all events
if all times are allowed.
A Transect View is a vertical cross section at any azimuth with
preset end locations, depth and thickness.
