UNAVCO IDV: Earth Strain Data and Displays UNAVCO IDV: Earth Strain Data and Displays The IDV can show strain measurements and models' data. Display types include point values, fields contoured or colored by values, and special symbols. You can do computations in the IDV. The IDV lets you include related data displays such as GPS velocity vectors and tomography models. Here are some examples.

GSRM 2nd invariant of strain rate and plate velocity vectors with GSRM plate motion relative to the Eurasian plate. Click for full size.

GSRM 2nd invariant strain rate and GSRM velocity field (no net rotation), over NASA Blue Marble surface image.

GSRM Data Sources for the UNAVCO IDV:

"In 1998 the International Lithosphere Program (ILP) initiated a new project: 'A Global Strain Rate Map' (ILP II-8). The mission of the Global Strain Rate Map (GSRM) project is to determine a globally self-consistent strain rate and velocity field model, consistent with geodetic and geologic field observations. " (from GSRM Introduction). NetCDF file for IDV use:

global grid of second invariant strain rate: gsrm.nc (netcdf variable name is "sisr")
Enter the URL link location into the IDV Data Chooser URLs window.
global plate velocities: see Plate Motion Vectors (GSRM Plate Velocities)

GSRM Publications:

Kreemer, C, A.J. Haines, W.E. Holt, G. Blewitt, and D. Lavalée,"On the determination of a globa strain rate model, Earth Planets Space, 52, 765-770, 2000; ( pdf copy online)
Kreemer, C., and W.E. Holt, A no-net-rotation model of present-day surface motions, Geophys. Res. Lett., 28, 4407-4410, 2001.
Kreemer, C., W.E. Holt, and A.J. Haines, The global moment rate distribution within plate boundary zones, in Plate Boundary Zones, eds. S. Stein and J.T. Freymueller, Geodynamics Series, v.30, 10/1029/030GD10, AGU, Washington D.C., 2002.
Kreemer, C., W.E. Holt, and A.J. Haines, "An integrated global model of present-day plate motions and plate boundary deformation," Geophys. J. Int., 154, 8-34, 2003. (pdf copy online)

GSRM Data Source Web Site:

Global Strain Rate Map Project (http://gsrm.unavco.org/),
Global Strain Rate Map : Results for version 1.2 (http://geodesy.unr.edu/cornekreemer/gsrm.htm)
GSRM Model Results online: Global Strain Rate Map Project: Model Results

IDV Displays:

IDV Computations

The IDV includes computations, such as finding the horizontal divergence of a vector field.

see "Computing Plate Divergence from GSRM Velocities and the Lithgow-Bertelloni & Richards Historic Plate Motions with the UNAVCO IDV"

UNAVCO IDV globe view of 'horizontal divergence' of the GSRM 'no net rotation' velocity field, Americas. Red and orange areas are positive divergence (crustal extension or spreading), and blue areas are negative divergence, crustal contraction or subduction. Note that divergence is not the same as the second invariant of strain rate. Click for full size.