Given an existing 3D velocity model defined by interpolation between control point nodes and created by velocity inversion programs such as SimulPS, Simul2000 and FDTomo to a 3D model grid. (outputs a 3D Grid) , Vel2Grid3D generates a 3D model Grid header and buffer files containing velocities, slownesses or other model specification.
Overview - Running the program-Input - Output - Processing and Display of results - [NonLinLoc Home]
The Vel2Grid3D program converts an existing 3D velocity model defined by interpolation between control point nodes and created by velocity inversion programs such as SimulPS, Simul2000 and FDTomo into a 3D Grid file containing velocity or slowness values.
The Vel2Grid3D program uses a "flat earth", rectangular, left-handed, x,y,z,t coordinate system (positive X = East, positive Y = North, positive Z = down). Distance units are kilometers.
Because of there are many variations of
the SimulPS, Simul2000 and FDTomo type model formats, it is necessary
to edit the Vel2Grid3D.c source code to select a specific sub-format
The current options are:
1. default, early SimulPs format with %5f (fixed width) format for reading velocity values and right-handed, East-negative coordinate system
2. Zhang %7f (fixed width) format for reading velocity values and left-handed, East-positive coordinate system
3. ETH format (*f variable width, space delimited) for reading velocity values
4. A left-handed, East-positive coordinate system
The Vel2Grid3D program takes a single argument
which specifies the complete path and filename for an Input
Control File with certain required and optional statements
specifying program parameters and input/output file names and
locations. See the Vel2Grid3D
Statements section of the Input Control File for more details.
Note that to run Vel2Grid3D the Generic
Statements section of the Input Control File must contain the
(Geographic Transformation) statements.
In addition, the Vel2Grid3D program requires a set of Vel2Grid Statements and Vel2Grid3D Statements in the Input Control File:
Vel2Grid statements: VGOUT, VGGRID, VGTYPE
Vel2Grid3D statements: VGINP, VGCLIP. VGINP sets the input format type (FDTOMO or SIMUL2K) and input velocity grid parameters for SIMUL2K. VGCLIP allows: 1) if Vmin < Vmax: setting minimum and maximum clip limits for the output velocity values; or 2) if Vmin > Vmax: sharpening of velocity difference across an interface (such as the Moho): if velocity at node below current input node is > Vmax: set the NLL grid point velocity equal to the velocity of the deepest overlying input node with velocity<Vmax.
The velocity or
slowness values throughout the requested grid are written to a new 3D
Grid File. For a description of the naming convention for these
grid files, see the
statement in the Vel2Grid Statements section of the Input Control
The 3D model grids can be post-processed with the program Grid2GMT to produce a GMT command script for plotting with the GMT plotting package.
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