Seismic Anisotropy Displays in the GEON IDV
The GEON IDV can display
seismic polarization
with the
conventional symbol centered on the earthquake location
in latitude, longitude, and depth.
Splitting azimuth and delay are shown at each station
as bars aligned with the fast direction and bar length scaled by time delay.
Display can include regular map views and a rotatable 3D globe, and may include time animation. The IDV has full interactive controls in 3D including zoom, pan, and rotation, and a tools to change map projections and background maps.
You can overlay other geophysical, GIS, and map data.
How To Run the IDV
To install and start the GEON IDV, see
Download & Run the GEON IDV.
To load data in the GEON IDV and make displays, see
How to use the GEON IDV.
Data Available Online
Published data has been made available online for the GEON IDV
by UNAVCO and GEON. See
Data Online for the GEON
IDV.
Making Data Files for Seismic Polarization
The GEON IDV uses data files with NetCDF format. NetCDF is a machine-independent
binary format used by hundreds of research organizations, and contains rich
metadata about the data, such as full attribution about the creators of the data.
To create a data file that the GEON IDV can read, see
GEON IDV Data Formats and Access Methods
Note that anisotropy data are "point data."
Generally you make an ascii CDL format
first, then convert to the binary NetCDF file. See
NetCDF data for the GEON IDV.
Sample CDL file for seismic polarization.
Note that all the variable names such as "phi" and "azimuth_error" are specially recognized by the GEON IDV
and need to be exactly as shown. (Only the GEON version of the IDV can show sesimic polarization symbols).
Depth can be 0 if you wish.
Sample NetCDF file for seismic polarization
(binary version of the data in the sample CDL file)
This data is from Table 3 in
"Models of lithospheric and asthenosphere anisotropic structure of the Yellowstone hotspot from shear wave splitting" by
Gregory P. Waite, Derek L. Schutt, Robert B. Smith, and Eugene D. Humphreys.
Bundle file for a display using the same data.
Read about
IDV Bundle Files.
Make a Display
When you select point data such as seismic observations, be sure to choose the
"NetCDF Point Data files" for "Data Source Type" in the "Data Source Chooser" window,
before you click on the data source name.
After the IDV connects to the data (you added a data source) , then in the "Fields Selector" window,
in the Fields panel, you should see "Point Data." (If not, the file is bad or
you did not tell the IDV it was point data. )
To make a data display,
in the Displays panel click on the circle by "Point Data," then on "Point Data Plot."
Click on Create Display. ("Point Data List" shows a list of data values.)
A display appears in the main
window and a Display Controls window pops up.
In the main menu bar, choose a Projections -> Set that suits your area, or make a
new Projection to do so. See more about Projections in the how-to page.
In the Display Controls window,
choose "Station Model" to be "Seismic polarization."
The symbols are located at the location and depth of the observation.
Read more about Point data plot controls.
unavco.org).