Comments from FORTRAN code
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c c
c Program: PRONTO c
c Programmer: D.F. Aldridge c
c Last Revision Date: 5 May 1998 c
c c
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c Program PRONTO performs a tomographic inversion of first arrival
c traveltimes to obtain two-dimensional velocity model.
c
c Run Parameters:
c
c dxz: grid interval (m).
c
c xmin_xtend: slowness model expansion distance in -x direction (m).
c xmax_xtend: slowness model expansion distance in +x direction (m).
c zmin_xtend: slowness model expansion distance in -z direction (m).
c zmax_xtend: slowness model expansion distance in +z direction (m).
c
c tmin: minimum observed traveltime to use in inversion (s).
c tmax: maximum observed traveltime to use in inversion (s).
c
c Parameter defining `zeroth derivative' constraints:
c
c mu0: weight.
c
c
c Parameters defining first derivative constraints:
c
c mu1_h: horizontal derivative weight.
c mu1_v: vertical derivative weight.
c mu1_d: directional derivative weight.
c theta1: angle (rel to +x) of directonal derivative (deg).
c
c
c Parameters defining second derivative constraints:
c
c mu2_h: horizontal derivative weight.
c mu2_v: vertical derivative weight.
c mu2_d: directional derivative weight.
c theta2: angle, rel to +x, of directional derivative (deg).
c mu2_m: mixed derivative weight.
c
c
c xwidth: horizontal width of smoothing filter (m).
c zwidth: vertical width of smoothing filter (m).
c cwait: center value of `tent-shaped' weight distribution.
c
c iop_vin: option flag for initial velocity model:
c 1=generate internally from linear velocity formula.
c 2=read from external file #12.
c
c Parameters defining linear initial velocity model (only used
c if iop_vin=1):
c
c xo_in: horizontal coordinate of reference point (m).
c zo_in: vertical coordinate of reference point (m).
c vo_in: velocity at reference point (m/s).
c a_in: magnitude of velocity gradient (1/m).
c phi_in: direction angle, rel to +x, of velocity gradient (deg).
c
c
c iop_vref: option flag for reference velocity model:
c 0=same as initial velocity model.
c 1=generate internally from linear velocity formula.
c 2=read from external file #13.
c
c Parameters defining linear reference velocity model (only used
c if iop_vref=1):
c
c xo_ref: horizontal coordinate of reference point (m).
c zo_ref: vertical coordinate of reference point (m).
c vo_ref: velocity at reference point (m/s).
c a_ref: magnitude of velocity gradient (1/m).
c phi_ref: direction angle, rel to +x, of velocity gradient (deg).
c
c iop_topo: surface topography option flag:
c 0=ignore.
c 1=horizontal surface with fixed vertical coordinate.
c 2=read surface topography function from file #14.
c z_topo: z-coordinate of a horizontal surface (m).
c v_reduce: velocity reduction factor above topographic surface.
c airspeed: speed of sound in air (m/s).
c
c iop_tout: option flag for traveltime/residual output:
c 0=no output.
c 1=write final predicted traveltimes to file #16.
c 2=write final predicted traveltime residuals to file #16.
c
c errlim: rms traveltime residual for terminating iterations (s).
c tcutoff: upper limit for including residuals in inversion (s).
c
c niter: maximum number of tomographic iterations.
c itmax: maximum number of LSQR iterations.
c
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c Input/Output:
c
c 1) Run parameters are read from file #10.
c
c 2) Observed data is read from file #11.
c
c Source and receiver coordinates, observed traveltimes, and
c data weights are organized in a `source gather' format within
c input file #11. Data are read with the fortran code:
c
c read (11,*) nshots
c do 1 i=1,nshots
c read (11,*) xs,zs,nrecs(ishot)
c do 1 j=1,nrecs(ishot)
c 1 read (11,*) xr,zr,tobs,wait
c
c where
c
c nshots = total number of source gathers.
c (xs,zs) = source x and z coordinates (m).
c nrecs(ishots) = number of receivers in current source gather.
c (xr,zr) = receiver x and z coordinates (m).
c tobs = observed traveltime (s).
c wait = datum weight (dimensionless).
c
c 3) Initial velocity model is read from file #12.
c
c Three columns of values are read from input file #12 with
c the fortran code:
c
c do 1 j=1,nz
c do 1 i=1,nx
c 1 read (12,*) x,z,v(i,j)
c
c where
c
c v(i,j) = velocity value associated with coordinates
c
c x=xmin+(i-1)*dx z=zmin+(j-1)*dz.
c
c 4) Reference velocity model is read from file #13.
c
c Format of input velocity file #13 is identical to input
c velocity file #12.
c
c 5) Surface topography function is read from file #14.
c
c Format of input topography file #14 is a list of coordinate
c pairs defining the surface topography. File #14 is read
c read with the fortran code:
c
c read (14,*) nsurf
c do 1 i=1,nsurf
c 1 read (14,*) xsurf(i),zsurf(i)
c
c where
c
c xsurf(i) and zsurf(i) are horizontal and vertical
c coordinates of a point on the topographic surface.
c
c 6) Final velocity model is written to file #15.
c
c Format of output velocity file #15 is identical to input
c velocity file #12.
c
c 7) Final raypath density map is written to file #16.
c
c Three columns of values are wriiten to output file #16 with
c the fortran code:
c
c do 1 j=1,nz-1
c z=zmin+(j-0.5)*dz
c do 1 i=1,nx-1
c x=xmin+(i-0.5)*dx
c 1 write (16,*) x,z,rayden(i,j)
c
c where
c
c rayden(i,j) = raypath density value associated with
c coordinates x and z.
c
c 8) Final predicted traveltimes (or traveltime residuals) are
c written to file #17.
c
c Format of data output file #17 is identical to data input
c file #11.
c
c 9) Diagnostic information is written to standard output (file #6)
c during run time. To store this info in an external file,
c redirect standard output to a named file name via the UNIX
c command `pronto.exe > filename'.
c
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c
c Fortran Code Compilation:
c
c UNIX command `f77 pronto.f -o pronto.exe' generates a compiled
c code file named `pronto.exe' from source code file `pronto.f'.
c
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c
c Array Size Specification:
c
c The following parameters, all suffixed by _dim, limit the size of
c the problem that can be handled.
c
c 1) Max dimensions of slowness grid: nx_dim horizontal points
c by nz_dim vertical points. nxzmax_dim should be
c set equal to the larger of nx_dim and nz_dim.
c 2) Max no. of traveltimes: ndata_dim.
c 3) Max no. of equations to solve: neqats_dim.
c 4) Max no. of square cells in slowness model: ncells_dim.
c 5) Max no. of nonzero elements in Jacobian matrix: njaco_dim.
c 6) Max no. of traveltimes per shot gather: nrecmax_dim.
c 7) Max no. of sources: nshots_dim.
c 8) Max no. of horizontal points in smoother: nxw_dim.
c 9) Max no. of vertical points in smoother: nzw_dim.
c
c Array dimensions should be increased with the fortran `parameter'
c statements below in order to treat larger sized problems.
c
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parameter (nx_dim =1001)
parameter (nz_dim =501)
parameter (nxzmax_dim =1001)
parameter (ndata_dim =100000)
parameter (neqats_dim =500000)
parameter (ncells_dim =300000)
parameter (njaco_dim =3000000)
parameter (nrecmax_dim=1000)
parameter (nshots_dim =1000)
parameter (nxw_dim =100)
parameter (nzw_dim =100)
Return to PRONTO documentation.