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Table of Contents for GEON IDV web site Introducing the GEON IDV GEON IDV: Data Displays & Analysis Capabilities     GPS Velocity Vectors & Error Elipses     Earthquake Locations and Magnitude     Earthquake Focal Mechanisms     Seismic Anisotropy     Seismic Tomography     REM Global Seismic Tomography Data     Mantle Models' Tomography     Topography Data and 3D Relief Maps     Yellowstone Geophysics Example     Particle Plume Dispersion     Earth Strain Imagery     Tracks or Seismic Ray Paths     GSRM Tectonic Plate Motion Vector Grids     Earth Strain Axes Download & Run the GEON IDV How to Use the GEON IDV: Basics     More Tips "True 3D" with the GEON IDV Data Online: The GEON Portal, and the UNAVCO Catalog GEON IDV Data Formats and Access Methods NetCDF Data for the GEON IDV UNAVCO's ASCII to NetCDF Data Converters

GEON IDV: Seismic Raypaths and other Track Displays in 3D

The IDV can display seismic ray paths, or any track, in 3D, in any area from small regions to the entire Earth. A track is a sequence of latitude, longitude, altitude or depth, and time values. The track may optionally have parameter values at each location along the path, such as seismic velocity or temperature, and the track may be colored by parameter value or by depth or altitude along the track.

Tracks can show aircraft track colored by a sensed value, or any other path over or in the earth with optional coloring by value along the track. Track displays are sequences of straight line segments drawn between point pairs. They can be used to draw simple line figures, such as outlines of a data sample regions based on some location values.

Track and Seismic Raypath Data

The IDV reads data from NetCDF formatted files (see IDV Data Formats: NetCDF ). A NetCDF data file for a simple ray path is located on the UNAVCO GEON web server at URL http://geon.unavco.org/unavco/NETCDF/raypath_P_wave_30deg_p3.nc. This file has no parameter values along the path, just the track location latitude, longitude, and depth (and time).

A short but more detailed track data file is is at URL http://geon.unavco.org/unavco/NETCDF/short_raypath_Illinoisp3.nc. This has and P wave velocity parameter values along a short path in the central US. You can make a track display colored by the parameter values (or colored by depth or the other coordinates). The data values in these files are synthetic.

To connect this data to the IDV:

• either download one of the data files to your disk, then use the IDV's Dashboard Data Chooser for "Files",
• or simply add the whole URL above to the Dashboard's Data Chooser's "URLs."

In the Dashboard Field Selector, Data Sources panel, the data source location and file name should be listed.

Make a Display

After the IDV connects to the data, to make a display, use the IDV Dashboard's "Field Selector." In the "Fields" panel you should see "Track." To make a data display, open the blue button by "Track." Click on "altitude" to plot just the path colored by altitude, then in the "Displays" panel choose Charts->Track. Or in Fields click on on "P wave velocity" the name of the parameter along the path when using the short_raypath_Illinoisp3.nc file to color the path by the P velocity values in the data file. Click on Create Display. In the display control window that appears, you can change the color table, and range (data value limits) on the color table.

Also you can, in Fields, choose "Point Data -> Point Data List" to see a list of data values.

For a color table showing depth in the mantle, use a color table range of about -2800000.0 to 0 meters. The track or raypath display appears to work in meters, not km, even if your data is in km and you give km as the units.

Making Data Files for Seismic Ray Paths

Store data in NetCDF files; see IDV Data Formats: NetCDF

Track data files use a special NetCDF format . The NetCDF ascii ".cdl" file for the first raypath data set (no parameter) is online at raypath_P_wave_30deg_p3.cdl, and the second data set (one parameter) has short_raypath_Illinoisp3.cdl. You make NetCDf ".nc" cross-platform binary files from a ".cdl" file.

The data is a collection of one-dimensional arrays of latitude, longitude, altitude, parameter values, and time values, each array having the same number of entries. Time values must be present and montonically increasing but need not be meaningful. Track data displays were originally designed for aircraft data; using all the same time values makes an error.

Parameter data is optional. The parameter in the second sample file is Pv; the parameter could be any value along the path, such as temperature or any scalar value. A track or ray path data file need not have any parameter information; only the path itself would be plotted in that case (and colored by depth or altitude if you like).

NetCDF .nc filenames of raypath (track) data may end with "p3.nc" for the IDV to recognize track data automatically. Otherwise you must choose data type "Track data" in the Data Chooser.

Tracks for Paths and Outlines

You can use track data to draw paths or outlines showing features, data regions, etc.

An example CDL file is box_outline_p3.cdl , and its binary NETCDF .nc file is box_outline_p3.nc . This draws a box inside Colorado.

Oblique view of a track (seismic P wave ray path) in Illinois, U.S.A., colored by parameter value (P wave velocity).

Globe view of four P wave paths through the mantle, colored by depth; core is grey surface. Earthquakes are also shown, colored by magnitude. The IDV display is a rotatable 3D globe.