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Table of Contents for GEON IDV web site Introducing the GEON IDV GEON IDV Displays, and Data from UNAVCO and GEON Download & Run the GEON IDV Tutorial ... How to Use the GEON IDV ... More Tips Data Formats: How to Put Your Data in the IDV

GEON IDV Tutorial

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Part 6 - Standard Earth Seismic Models - Model Differencing - Seismicity Plots (more) - Surface Wave Dispersion &c.

Standard Earth Seismic Models

UNAVCO makes available standard whole-earth seismic models for use in the IDV.  

If you have a globle display window open, close it. We will use the map display for this example
Click on the main menu choice "Projections" and check ON the item "Reset Projection with New Data."

Set the vertical scaling for the 3D display. Choose, on the display menu, the menu choice 
"View -> Viewpoints -> Vertical Scale." In the window that
appears, enter "Min value:" -6371.0, "Max value:" 0.0, and for "Units" choose "km" (kilometer). Click the "OK" button.
Choose the main menu choice "View -> Show" and check "Show wireframe box" if it is not checked already.

in the Dashboard window, click the tab "Data Chooser," and click on the "URLs" tab.
Enter  http://geon.unavco.org/unavco/NETCDF/PREM_Vp_Vs_3Dgrid.nc in the "URL" entry box 
Then click on the "Add Source" button. This is a global 3D grid of VP and Vs velocities made from the PREM model.

The PREM model has no lateral variations, only changes with depth, so displays of plan views and 
isosurfaces are uninteresting.  You can make vertical cross sections colored by value, and vertical profiles:

The AK135 model is also available at http://geon.unavco.org/unavco/NETCDF/AK135_3Dgrid.nc. It has Vp, Vs, and density.

Model Differences

You can find difference between any two data sets of the same parameter in the IDV.  As an example we will difference
a tomography seismic model and the AK135 model.

You can easily use multiple data sets from different sources - the IDV automatically takes care of grids with different coverages 
data location grid points, and units. 

Choose, in the Dasgboard's Field Selector's Data Sources, "Formulas," then "simple difference" in the Fields panel. 
Click on the "Displays" type that you use to make. Click Create Display. A window opens shwoing two panels of all the data that
you are connected to. Click on the data sources to differ.  

Isosurface and vertical cross section of 3D Vs tomography results minus AK135 Vs

The IDV has a facility to make more complex computations on your data using the Python computer language. Results are shown as IDV displays. See IDV Data Analysis (from Unidata).

Seisimcity Plots - more details

Here are more detailed plots of seismicity using example data under Japan provided by Francis Wu of Binghamton University.

Use a map display; not a globe display, and do main menu choice Edit -> Remove all displays." Do main menu choice "Projections ->
Set -> Japan." Set the vertical scale (View->Viewpoint->vertical scale) to Min -500 and Max 0 kilometers.

Choose URL data sources; Data Type "Netcdf point data." Add Data Source with URL 
http://geon.unavco.org/unavco/Kanto/F_Wu_eq_foc_mech_sample.nc. Click "Create Display" for "Point Data Plot."

In the displays window check off the "Declutter" box. Zoom in a little, and rotate to see earthquakes with depth. You will
be seeing blue crosses at locations. In the Display control, choose "Station Model" to be "Earthquake mags by color," then 
switch to "Earthquake depths by color." Zoom, pan, and rotate to see the locations in 3D. You should see something like this:

Japan earthquake locations colored by depth, in 3D oblique view

Switch the "Station Model" to "Focal mechanism, lower half sphere." (There is a pause while the 3D focal mechanisms are generated).

Japan earthquake focal mechanisms, in 3D oblique view

You can include any of this earthquake focal plots witn any other GEON IDV plot, such as raypaths.

Surface Wave Dispersion

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