DOCUMENTATION AND RELATED PROGRAMS
Version 1.4.2
Written by: Colin A. Zelt
Presently at:
Rice University
Houston, Texas 77005
USA
email: czelt@rice.edu
Version 1.4.2
Written by: Colin A. Zelt
Presently at:
Rice University
Houston, Texas 77005
USA
email: czelt@rice.edu
A 2-D (x,z) isotropic medium is assumed. The velocity model is composed of a sequence of layers separated by boundaries consisting of linked linear segments of arbitrary dip. Layer boundaries must cross the model from left to right. Layer thicknesses may be reduced to zero to model pinchouts or isolated bodies. The velocity within a layer is defined by velocity values specified at arbitrary x-coordinates along the top and bottom of the layer. The x-coordinates at which layer boundaries and upper and lower velocities are specified can be completely general and independent within and between layers. Velocity discontinuities across layer boundaries are allowed but not required. For the purposes of ray tracing, the model is automatically broken up into an irregular network of trapezoids, each with dipping upper and lower boundaries and vertical left and right sides. The velocities at the four corners of the trapezoid are used to interpolate a velocity field within the trapezoid so that the velocity varies linearly along its four sides. Therefore, horizontal as well as vertical velocity gradients may exist within a trapezoid. A simulation of smooth layer boundaries is possible in which the incident and emergent ray angles are calculated using the slope of the smoothed boundary.
The source(s) may be positioned anywhere in the model and rays may be directed any angle. The receivers are always assumed to be at the top of the model. Both P- and S-wave propagation can be considered including (multiple) conversions. A unique Poisson's ratio may be assigned to each trapezoid of the model. Refracted, reflected and head waves may be traced, each possibly containing multiple and/or surface reflections and conversions. Ray take-off angles are determined automatically by the program for those ray groups specified by the user using an iterative shooting/bisection search mode. Ray tracing is performed by numerically solving the ray tracing equations for 2-D media, a pair of first order ODE's, using a Runge-Kutta method. The ray step length is automatically adjusted at each step to maximize efficiency while maintaining accuracy. Travel times are calculated by numerical integration along ray paths using the trapezoidal rule. A plot of the model and all rays traced may be produced along with a plot of reduced travel time versus distance for the observed and calculated data.
The partial derivatives of travel time with respect to those model parameters selected for adjustment are calculated analytically during ray tracing; these parameters include velocities and the vertical position of boundary nodes. The travel times correspond to any ray paths which can be traced through the model, being either first or later arrivals. The travel time residuals with respect to the observed data are also calculated. The travel times and partial derivatives are linearly interpolated to the observed seismogram locations since two-point ray tracing is not required. The partial derivatives and travel time residuals are output and used later as input to the program DMPLSTSQR which updates the model parameters by applying the method of damped least-squares to the linearized inverse problem.
The model parameterization is well suited to the inversion of
refraction/reflection data since realistic earth models can be
represented by a minimum number of model parameters, i.e., the
number and position of parameters specifying each layer can be
adapted to the data's subsurface ray coverage. Layer boundaries,
including the surface, may be horizontal (one parameter) or
consist of numerous straight line segments. A layer may have a
constant velocity (one parameter) or the velocity structure may be
defined by many upper and lower layer velocity points. Different
velocity points may be specified above and below a layer boundary
if a velocity discontinuity is required across the boundary, or a
single row of velocity points may be specified if an interface
with no discontinuity is needed. The vertical velocity gradient
or layer thickness may be fixed in all or part of a layer during
the inversion if there is insufficient ray coverage to
independently determine an upper and lower layer velocity or layer
thickness.
Executable file: RAYINVR
Input file: r.in contains program input parameters in five parts:
The above sequence of nine lines is repeated for each model layer, the top-most layer specified first, the bottom-most last, and is ended by specifying the bottom layer boundary of the model as in (a) and (b) above. If the number of points defining a boundary or the upper or lower velocity of a layer must exceed 10 then the points can be continued onto subsequent lines of the file as follows: line (b), (e) or (h) of the particular parameter to be extended is modified to include a 1 in the second column so the complete format of the line becomes I2, 1X, 10F7.2. The sequence of three lines (a)-(c), (d)-(f) or (g)-(i) is then repeated as many times as is necessary using the same format described above.
Please see the Additional Notes section for methods of simplifying the input model for such cases as:
Input file: v.in contains the velocity model in the same format as described in part (5) above for r.in.
Input file: f.in contains the "floating" reflecting boundaries; these are interfaces with no associated velocity discontinuity (hence the word "floating") at which rays can reflect in addition to the layer boundaries; the file format is similar to that for v.in:
Input file: tx.in contains the observed travel time-distance pairs in the following format:
Output file: tx.out contains the calculated travel time-distance pairs in the same format as described above for tx.in.
Output file: r1.out contains summary information for each ray traced including the shot number, take-off and emergent angle, range, reduced travel time, number of points (step lengths) defining the ray and the ray code.
Output file: r2.out contains detailed parameters for each trapezoid of the velocity model, a one-dimensional equivalent (average) velocity model and summary information for each point of each ray traced.
Output file: i.out contains the partial derivatives, travel time residuals and travel time uncertainties used for input by the program DMPLSTSQR. The top of the file contains the following information:
Output file: p.out contains all plot commands for the run used for input by the program RAYPLOT.
Output file: n.out contains the namelist parameter values.
iroute - equals 1 to plot to the screen, 2 to create a postscript file, 3 to create a plot file for the VERSATEC plotter, or 4 to create a colour postscript file; if iroute does not equal 1 there is no plotting to the screen (default: 1)
iseg - create a Uniras segment(s) (default: 0)
iplot - generate the plot during the run (1), or write all plot commands to the file p.out (0), or do both (2) (default: 1)
imod - plot model boundaries (default: 1)
ibnd - plot vertical model boundaries (default: 1)
idash - plot model boundaries as dashed lines (default: 1)
ivel - plot the P-wave (1) or S-wave (-1) velocity values (km/s) within each trapezoid of the model (default: 0)
iray - plot all rays traced (1) or only those which reach the surface (or reflect off the floating reflector for ray groups for which frbnd>0) (2); rays traced in the search mode are not plotted unless irays=1 (see below) (default: 1)
irays - plot the rays traced in the search mode (default: 0)
irayps - plot the P-wave segments of ray paths as solid lines and the S-wave segments as dashed lines (default: 0)
idot - plot a symbol at each point (step length) defining each ray path (default: 0)
itx - plot the calculated travel time-distance values as lines (1), symbols of height symht (2), symbols of height symht interpolated at the observed receiver locations contained in the file tx.in (invr=1 must be used, if not, itx=2 is used) (3); or as residuals measured from the oberved data in tx.in (invr=1 must be used) (4); no calculated travel times are plotted if itx=0 (default: 1)
itxbox - plot only those calculated and observed travel times that have distances between xmint and xmaxt and times between tmin and tmax (default: 0)
idata - plot the observed travel time picks from the file tx.in (1 or -1), or plot only those picks used in the inversion if invr=1 (2 or -2); the observed data are represented by vertical bars with a height of twice the corresponding uncertainty specified in the file tx.in if idata>0, or by symbols of height symht if idata<0 (default: 0)
isep - plot the model and rays and travel times in the same plot
frame (0), separate plot frames (1), plot the model and rays and
travel times in a separate plot frame for each shot (2), or plot
the model and rays in separate plot frames for each shot followed
by the travel times in separate plot frames for each shot (3)
(default: 0) ibreak - an array corresponding to the ray groups listed in the
array ray to split travel time-distance curves into prograde
and retrograde segments when plotting with itx=1, and to increment
the integer code by one in the file tx.out when changing from a
prograde to retrograde segment or vice versa if itxout=1
(default: 1)
iszero - plot the calculated and observed travel times as if all
shot points were at 0 km and the rays travelled left to right
(default: 0)
itxout - write the calculated travel time-distance pairs to the
file tx.out; the integer code identifying each pick is
determined by the array ibreak if itxout=1 or the array ivray
if itxout=2 or 3; if itxout=3, the calculated travel times are
interpolated to the observed receiver locations (invr=1 must be
used if itxout=3, if not, itxout=2 is used) (default: 0) idump - write detailed velocity model and ray tracing
information to the file r2.out and the namelist parameter
values to the file n.out; mainly for debugging (default: 0)
Note: using idump=1 will greatly slow down the run time
isum - write a short summary about the rays traced and the
velocity model to the screen (1), also write the travel time
residuals and chi-squared values for each phase and shot to the
file r1.out (2), and to the screen (3) (must use invr=1 for
isum>1) (default: 1)
istep - pause after each ray is plotted writing its take-off angle
to the screen and waiting until a
Note: the value of isep may be changed during a program run with
entry from the keyboard of the values 0, 1, 2 or 3 between
plot frames when a
Note: there appears to be a bug with itxout, itx=itxout may be
necessary for correct results
symht - height of symbols (mm) used when plotting each point defining a ray path, single point travel time curves (if symht=0, single point travel time curves will not be plotted), the calculated travel times if itx=2, or the observed travel times if idata<0 (default: 0.5)
velht - the maximum height of the velocity values (mm) when ivel=1 or -1 is equal to velht*albht (default: 0.7)
nskip - the first nskip points (step lengths) of all ray paths are not plotted (default: 0)
nrskip - plot every nrskip ray traced (default: 1)
npskip - plot every npskip point of each ray traced (default: 1)
vred - reducing velocity (km/s) of travel time-distance plot; observed data in the file tx.in is assumed to be unreduced (a value of zero is permitted for no reduction; vred must be less than 10) (default: 8)
xwndow, ywndow - the horizontal and vertical size of the graphics
window (mm) that will over-ride a window size specified in an
"mx11.opt" or ".Xdefaults" file; the maximum allowable values
(to use the entire screen) are 350 and 265 mm, respectively
(defaults: if xwndow or ywndow is less than or equal to zero,
the size of the window specified in the "mx11.opt" or ".Xdefaults"
file is used)
Note: the effect of these parameters will depend on the local graphics system and machine type
dvmax, dsmax - a warning message is written to the screen and the to file r1.out indicating the layers in which the magnitude of the velocity gradient vector is greater than dvmax (km/s/km) and the layer boundaries having a change in slope across three successive points of greater than dsmax (degrees) (defaults: infinite, infinite)
ibcol, ifcol - background and foreground colours (defaults: 0, 1)
mcol - an array specifying the colours of the model: the layer boundaries are mcol(1), the vertical boundaries are mcol(2), the floating reflectors are mcol(3), the smooth layer boundaries are mcol(4), and the velocity values are mcol(5) (default: 1, 1, 1, 1, 1)
ircol - colour the ray paths according to the value of ivray for that particular ray group (1), according to the shot number (2), or according to the ray group (3) (default: 0)
itcol - colour the observed travel times according to the integer code identifying each pick in the file tx.in (the 4th column) (1), or according to the shot number (2); if itcol=3, the observed travel times are coloured as if itcol=1 and the calculated travel times are coloured according to ray group (invr=1 must be used) (default: 0)
title - title for plot (up to 80 characters long) positioned using xtitle and ytitle (default: none) Not currently available on the UBC package.
xtitle, ytitle - x and y position (mm) of the plot title (default: 0, 0) Not currently available on the UBC package.
colour - an array specifying the colours of the ray paths if ircol > 0 and the observed travel times if itcol > 0. [default: 2 (blue), 3 (green), 4 (yellow), 5 (magenta), 6 (light blue),8,17,27,22,7]
modout - output discretised velocity model (ARG 8.8.99)
dxmod - size of increment in x direction for discretised output model, v.out. (ARG 15.10.98)
dzmod - size of increment in z direction for discretised output model, v.out. (ARG 15.10.98)
xmmin and xmmax - minimum and maximum x co-ordinates for the output model, v.out (defaults to xmin and xmax) Note: zmin and zmax determine limits in z direction. (ARG 6.8.99)
modi - sample these layer boundaries (counting from the top) and output them (spaced at dxmod) after the model in the output file. (ARG 6.8.99)
plotdev - used to plot output to screen or file. At UBC, there are two options: plotdev='x11 -geometry 1000x800' plots to the screen in a box that is 1000 pixels wide by 800 pixels high or plotdev='postlandfile xxx.ps' plots to a postscript file named xxx.ps. (ARG 16.9.98)
frz -
xmin1d -
xmax1d -
ifd -
dxzmod -
iaxlab - plot axes labels (default: 1)
itrev - draw the time-distance plot with the time increasing downward (default: 0)
albht - height of axes labels (mm) (default: 2.5)
xmin, xmax - minimum and maximum distance (km) of velocity model
xmm - length of distance axis (mm)
xtmin, xtmax - minimum and maximum values (km) of tick marks
ntickx - number of intervals separated by tick marks along distance axis
ndecix - number of digits after decimal in distance axis annotation; -1 for integer annotation (defaults: 0, none, 250; values for xtmin, xtmax, ntickx and ndecix depend on values of xmin and xmax)
zmin, zmax - minimum and maximum depth (km) of velocity model
zmm - length of depth axis (mm)
ztmin, ztmax - minimum and maximum values (km) of tick marks
ntickz - number of intervals separated by tick marks along depth axis
ndeciz - number of digits after decimal in depth axis annotation; -1 for integer annotation (defaults: 0, 50, 75; values for ztmin, ztmax, ntickz and ndeciz depend on values of zmin and zmax)
xmint, xmaxt - minimum and maximum distance (km) of time-distance plot
xmmt - length of distance axis (mm)
xtmint, xtmaxt - minimum and maximum values (km) of tick marks
ntckxt - number of intervals separated by tick marks along distance axis
ndecxt - number of digits after decimal in distance axis annotation; -1 for integer annotation (defaults: xmin, xmax, xmm; values for xtmint, xtmaxt, ntckxt and ndecxt depend on values of xmint and xmaxt)
tmin, tmax - minimum and maximum time (s) of time-distance plot
tmm - length of time axis (mm)
ttmin, ttmax - minimum and maximum values (s) of tick marks
ntickt - number of intervals separated by tick marks along time axis
ndecit - number of digits after decimal in time axis annotation; -1 for integer annotation (defaults: 0, 10, 75; values for ttmin, ttmax, ntickt and ndecit depend on values of tmin and tmax)
orig - lower left origin of plot is (orig,orig) mm (default: 12.5)
sep - separation (mm) between the model and travel time diagrams if isep=0 or 2 (default: 7.5)
ishot - an array specifying the directions rays are to be traced from the shot points listed in the arrays xshot and zshot; the following code is used:
iraysl - use the array irayt to select which ray groups listed in the array ray are to be traced for a particular shot point (default: 0)
irayt - an array selecting those ray groups listed in the array ray which are active for a particular shot point listed in the arrays xshot and zshot. If there are n ray groups listed in the array ray, then the jth ray group for the ith shot is referred to in the (2n(i-1)+j)th element of irayt for rays traced to the left , and in the (2n(i-1)+n+j)th element of irayt for rays traced to the right. You must specify values of irayt for each group and for each direction regardless of the values of ishot (default: 1)
ifast - use a Runge-Kutta routine without error control to solve
the ray tracing equations and a look-up/interpolation routine
to evaluate certain trigonometric functions; with ifast=0, a
Runge-Kutta method with error control and the intrinsic
trigonometric functions are used. Using ifast=1 is about 30-40%
faster and provides essentially the same accuracy as ifast=0
(default: 1)
Note: ifast=1 is intended to be used for all routine modelling
and ifast=0 only to test a final model or if ifast=1 obviously fails
i2pt - perform two-point ray tracing, i.e., determine the ray take- off angles that connect sources and observed receiver locations within each ray group; the receiver locations are obtained from the file tx.in for those picks that have the same integer code as specified in the array ivray for the ray group; if i2pt=2, only rays which reflect off the appropriate floating reflector specified in the array frbnd (if frbnd>0) are traced (default: 0)
iturn - an array corresponding to the ray groups listed in the array ray to trace rays only to their turning or reflection point in the search mode; if a refracted or head wave ray group is to contain a reflection(s) before it turns (specified using nrbnd and rbnd), then iturn=0 must be used (default: 1)
isrch - search again for the take-off angles of a ray group if the same ray code is listed more than once for the same shot in the array ray; isrch=1 must be used if the take-off angles of two or more ray groups with the same ray code are different because of multiple reflections and/or conversions specified by nrbnd, rbnd, ncbnd,and cbnd (default: 0)
istop - stop tracing any ray which reflects off a boundary not specified in the arrays ray or rbnd; if istop=2, rays are also stopped if they enter a layer deeper than that specified by the ray code in the array ray, i.e., the layer number is greater than L and the ray code is L.n, where n=0, 1, 2, or 3 (default: 1)
idiff - continue to trace headwaves along a boundary even if the velocity contrast across the interface is no longer positive, in which case headwaves emerge parallel to the boundary (idiff=1); if idiff=2, initiate a headwave ray group even if there is no critical point (or it is not found) to model diffractions along the top of a low-velocity layer (default: 0)
ibsmth - apply a simulation of smooth layer boundaries (1) or apply the simulation and plot the smoothed boundaries (2); ibsmth=2 has no effect if isep>1 (default: 0)
insmth - an array listing the layer boundaries for which the smooth layer boundary simulation is not to be applied, or only applied outside the model distances xminns and xmaxns, when ibsmth=1 or 2, (default: 0)
imodf - use the velocity model in the file v.in instead of the model in part (5) of the file r.in (default: 0)
xshot - an array containing the x-coordinates (km) of the shot points (default: 0.0)
zshot - an array containing the z-coordinates (km) of the shot points (default: a very small distance below the model surface)
ray - an array containing the ray groups to be traced; the following code is used: (1) L.1 - rays which refract (turn) in the Lth layer (2) L.2 - rays which reflect off the bottom of the Lth layer (3) L.3 - rays which travel as head waves along the bottom of the Lth layer (4) L.0 - ray take-off angles supplied by the user in the arrays amin and amax
nray - an array containing the number of rays to be traced for each ray group in the array ray (default: 10; however, the default is the first element of nray for all ray groups if only one value is specified)
space - an array which determines the spacing of take-off angles between the minimum and maximum values for each ray group in the array ray. For space=1, the take-off angles will be equally spaced; for space > 1, the take-off angles will be concentrated near the minimum value; for 0 < space < 1, the take-off angles will be concentrated near the maximum value (default: 1; however, space=2 for a reflected ray group if specified as L.2 in the array ray)
amin, amax - arrays containing minimum and maximum take-off angles (degrees); measured from the horizontal, positive downward and negative upward (for rays traveling left to right or right to left); used for ray groups specified by ray=1.0
nsmax - an array containing the maximum number of rays traced when searching for the take-off angles of the ray groups in the array ray (default: 10; however, the default is the first element of nsmax for all ray groups if only one value is specified)
n2pt - maximum number of iterations during two-point ray tracing (i2pt>0); this is the maximum number of rays traced for each receiver to determine the take-off angle of the ray that connects the source and receiver (default: 5)
x2pt - distance tolerance (km) for two-point ray tracing; less than n2pt rays will be traced for a particular receiver if a ray end point is within x2pt of the receiver location (default: (xmax-xmin)/2000)
crit - head waves are generated if a down-going ray in the search mode has an angle of incidence at the bottom of the Lth layer within crit degrees of the critical angle when ray=L.3 (default: 1)
hws - the spacing (km) of rays emerging upward from the bottom of the Lth layer when ray=L.3 (default: (xmax-xmin)/25)
nhray - maximum number of rays traced for a head wave ray group (default: pnrayf)
aamin - minimum take-off angle (degrees) for the refracted ray group in the first layer (default: 5)
aamax - maximum take-off angle (degrees) for reflected ray groups specified as L.2 in the array ray (default: 85)
stol - if a ray traced in the search mode is of the correct type and its end point is within stol (km) of the previous ray traced in the search mode, then the search for that ray type is terminated; a value of stol=0 will ensure that nsmax rays are always traced in the search mode (default: (xmax-xmin)/3500)
xsmax - for reflected ray groups specified as L.2 in the array ray, determine the minimum take-off angle using the search mode so that the maximum range for this ray group is xsmax (km) if iturn=0 or the maximum offset of the reflection point is xsmax/2 (km) if iturn=1; for head wave ray groups specified as L.3 in the array ray, the maximum offset of the point of emergence from the head wave boundary is xsmax (km); xsmax=0 will ensure that the take-off angle of the reflected ray which grazes off the bottom of the Lth layer is determined and head waves are traced along the Lth boundary until the edge of the model is reached (default: 0.0)
nrbnd - an array containing the number of reflecting boundaries for each ray group in the array ray (default: 0)
rbnd - an array containing the reflecting boundaries specified in the array nrbnd; the following code is used:
ncbnd - an array containing the number of converting (P to S or S to P) boundaries for each ray group in the array ray (default: 0)
cbnd - an array containing the converting boundaries specified in the array ncbnd; the following code is used:
frbnd - an array containing the floating reflecting boundaries for each ray group in the array ray; the values of frbnd correspond to the order in which the reflectors are listed in the file f.in (default: 0)
pois - an array containing the value of Poisson's ratio for each model layer; a value of 0.5 signifies a water layer with a corresponding S-wave velocity of zero (default: 0.25; however, the default is the first element of pois for all layers if only one value is specified)
poisl, poisb - arrays specifying the layers and block numbers, respectively, of model trapezoids within which Poisson's ratio is modified over that given by pois using the array poisbl; for poisb, the trapezoids with a layer are numbered from left to right
poisbl - an array containing the value of Poisson's ratio for the model trapezoids specified in the arrays poisl and poisb overriding the values assigned using the array pois
npbnd - number of points at which each layer boundary is uniformly sampled for smoothing if ibsmth=1 or 2 (default: 100)
nbsmth - number of applications of a three-point averaging filter to each layer boundary if ibsmth=1 or 2 (default: 10)
xminns, xmaxns - minimum and maximum model distance over which the layer boundaries listed in the array insmth are not to be smoothed using ibsmth=1 or 2 (defaults: smooth boundaries between xmin and xmax)
step - controls the ray step length in the solution of the ray tracing equations according to the relationship
step length (km) = step*v/(|vx|+|vz|)
where v is velocity and vx and vz are its partial derivatives with respect to x and z (default: 0.05)
smin, smax - minimum and maximum allowable ray step length (km) (defaults: (xmax-xmin)/4500, (xmax-xmin)/15)
nsmin -
ntan -
invr - calculate partial derivatives of the selected model parameters and write these to the file i.out (default: 0)
ivray - an array of non-zero integers corresponding to the ray groups listed in the array ray used to identify the type of arrival in the file tx.out if itxout=2 or 3 and to allow for the appropriate comparison with the observed travel times in the file tx.in if invr=1 or i2pt>0
ximax - the maximum allowable distance (km) between the nearest ray end point and an observed seismogram location for one of the rays used to interpolate the partial derivatives and travel time at that observed seismogram location (default: (xmax-xmin)/20)
ttunc - uncertainty of the calculated travel times (s) written to the file tx.out if itxout>0 (default: 0.01)
bndunc, velunc - estimated uncertainty of the depth of boundary nodes (km) and velocities (km/s) written to the file i.out (defaults: 0.1, 0.1)
Array defaults: if a single default value is indicated for an array parameter, all elements of the array have that default value.
Layer boundaries: must begin at xmin and end at xmax even if the layer above and/or below is pinched out (unless the boundary is defined by only one point, then it is specified at xmax).
Bottom layer boundary: should consist of at most ten points.
Near-vertical layer boundaries: should be avoided because they may result in large velocity gradients nearby. If necessary, the adjacent trapezoids should have zero velocity gradient.
Shot point locations: may be anywhere in the model, but locating them directly on a model boundary may cause problems.
Ray group: is defined as a set of rays specified by a ray code in the array ray, possibly modified to include multiple reflections and/or conversions, whose take-off angles are determined by an iterative search mode or specified by the user using ray=1.0 and the arrays amin and amax.
Zero velocity gradient: if the four corner velocities of a model trapezoid are equal, then there is a zero velocity gradient inside and no ray bending will occur. It is preferable to have a zero gradient in all or part of a layer rather than a very small gradient so that the Runge-Kutta routine can be avoided and straight ray paths are used.
Large velocity gradients: ray tracing becomes inaccurate if the velocity gradient is large and the ray step length is not small enough. In this case a warning message is given and the value of smin and/or step should be reduced.
Ray code: listed in the file r1.out for each ray traced is supplied as an internal check to ensure that the correct rays specified in the array ray or the arrays amin and amax have been traced. This ray code is determined by the program as follows: the number to the left of the decimal refers to the deepest layer encountered by the ray; the number to the right of the decimal will be one, unless (1) the ray was reflected upward from a layer boundary, in which case it will be two, or (2) the ray travelled as a head wave, in which case it will be three (assuming the ray was not reflected upward from a layer boundary after traveling as a head wave).
Shot point located at depth: in this case, the array ray should not contain ray codes corresponding to layers above the shot point.
Ray step length: a very small value of step may not result in increased ray tracing accuracy due to round-off error
Ray changes direction: a ray traveling left to right can reflect or refract and change direction and travel right to left, or vice versa.
Terminating a ray: if istop=0, a ray will be traced until it encounters the top, bottom, left or right of the model, unless it is reflected off the top of the model using nrbnd and rbnd.
Ray stopped warning: the warnings which begin "ray stopped -" are included in the file r1.out directly before the summary information for that particular ray is listed.
Failure of ray search mode: it is possible that the iterative shooting/bisection algorithm used in the ray search mode may fail, or find a limited range of take-off angles that only sample a part of a layer, if either (1) the model has large lateral variations, (2) the range of take-off angles defining the desired ray group is very small, (3) the value of nsmax is too small or stol is too large, or (4) it is not possible to trace the desired type of rays through a particular part of the model (i.e., violates Snell's law). In any case, increase the value of nsmax first and then decrease the value of stol if necessary and this should work (unless the problem is case 4). If this fails, take-off angles can be supplied manually using ray=1.0 and the arrays amin and amax. Use irays=1 to see why the search mode is failing.
Travel time curves: join successive points of the same ray code in the same ray group. Prograde and retrograde branches will be separated if ibreak=1.
Ray search mode and multiple reflections: for ray groups specified by L.2 in the array ray, the take-off angles determined in the search mode will correspond to rays which reflect off the Lth layer boundary only and may or may not give rise to the multiple reflections specified by nrbnd and rbnd .
Integer code in the file tx.out: is used to identify each travel time to allow for the appropriate comparison with the rays traced during inversion It will begin at one and be incremented one for each ray group if itxout=1. In addition, the integer will be incremented by one for a change from a prograde to retrograde branch or vice versa if ibreak=1. This may be undesirable if the prograde and retrograde branches should be identified by a single number for inversion or if more than one ray group should be identified by the same number, in which case itxout=2 or 3 and the array ivray should be used when writing to the file tx.out.
Laterally homogeneous layer: if a layer boundary is to be horizontal or the upper or lower velocity of a layer is to be constant, then only a single point is required in the velocity model and it should be specified at an x-coordinate equal to xmax. If two or more points are required, then the first and last point must be specified at xmin and xmax, respectively.
Constant velocity layer: to specify a layer with constant velocity, assign a single upper layer velocity at xmax and assign a lower layer velocity of zero at xmax.
Zero vertical velocity gradient layer: to specify a layer with zero vertical velocity gradient, assign one or more upper layer velocities as usual and assign a lower layer velocity of zero at xmax.
Zero velocity discontinuity across layer boundary: to specify a layer boundary with no associated velocity discontinuity, assign an upper layer velocity of zero at xmax for the layer directly beneath the boundary.
Fixed vertical velocity gradient: if the vertical velocity gradient is to remain fixed in all or part of a layer during the inversion, then the x-coordinates at which the upper and lower layer velocities are defined must be the same. Note that if the x-coordinates of the velocity values are not all the same as the location of the upper and lower layer boundary nodes, then it is possible for the velocity gradient to vary at these nodes since there are no velocities specified at these points and the upper and lower layer velocities are interpolated from values on either side, or at xmax if only one velocity point is used.
Fixed layer thickness: if the thickness of a layer is to remain fixed in all or part of a layer during the inversion, then the x-coordinates at which the upper and lower layer boundaries are defined must be the same.
Multiple ray paths to a single observation: if more than one pair of ray paths brackets the location of an observed travel time pick, then the pair of ray paths corresponding to the least interpolated travel time is used to calculate the travel time residual and the partial derivatives for the inversion.
Inversion of zero-velocity-discontinuity boundary: it is not possible to invert for a layer boundary with an associated zero-velocity discontinuity if only refracted rays cross the boundary, i.e., rays must be reflected off the boundary (although the physical meaning of reflections from a zero-velocity discontinuity must be considered).
Boundaries crossing after inversion: check that layer boundaries do not cross after inversion; if they do, re-do the inversion with increased damping or re-do the ray tracing with the appropriate boundary nodes held fixed or the thickness of the layer held fixed.
Inversion of layer pinchouts: for a few special cases there are bugs in the inversion code when attempting to invert model parameters associated with a layer pinchout.
S-waves and inversion: although rays corresponding to S-waves and conversions can be traced, they should not be traced if partial derivatives are being calculated for the purpose of inversion since the appropriate code to invert for S-wave velocity or Poisson's ratio has not yet been included.
External plot routines: RAYINVR is self-contained except for the
graphics calls inside the following CALCOMP or CALCOMP-like plot
routines: PLOTS, PLOT, NUMBER, SYMBOL, LINE, EMPTY, ERASE, PLOTND.
The file pltlib.f contains ALL these routines (and a few other
less important ones used by the graphics system where the
code was developed) and it will be necessary to replace the "call"
statements within each of these with their equivalents in the
local graphics package.
The parameters specifying the size of all arrays within RAYINVR are contained in the file rayinvr.par and may be altered to suit a particular problem and memory requirements.
model layers - player
points defining a single layer boundary (must be a multiple of 10) - ppcntr
points at which the upper or lower layer velocity is defined (must be a multiple of 10) - ppvel
trapezoids within a layer - ptrap
shot points - pshot
ray codes for a single shot - prayf
ray groups for all shots combined - ptrayf
rays in a single group - pnrayf
rays reaching the surface (not including the search mode) - pray
points defining a single ray - ppray
reflecting boundaries for a single ray - prefl
reflecting boundaries for all ray groups - preflt
converting boundaries for a single ray - pconv
converting boundaries for all ray groups - pconvt
points defining smooth layer boundary - pnsmth
trapezoids within which Poisson's ratio is modified - papois
model parameters for which partial derivatives are calculated for inversion - pnvar
travel time picks in the file tx.in - prayi
floating reflectors - pfrefl
points defining a single floating reflector - ppfref
iterations in two-point ray tracing search - pn2pt
travel times with the same integer code for a single shot - pnobsf
The following is a list and explanation of warning and error messages generated by RAYINVR:
*** error in velocity model *** - an error in the format of the velocity model in the file r.in or v.in has been detected. One of the following problems exists:
*** array size error for number of model points *** - the parameters specifying the maximum number of points defining a layer boundary (ppcntr) and/or the upper or lower layer velocity (ppvel) is not a multiple of 10
*** maximum number of blocks in layer _ exceeded *** - a layer in the velocity model will consist of more than the maximum number of trapezoids allowed for a single layer given the current form of the model. Reduce the number of points defining the upper and/or lower boundary or velocity for the particular layer.
*** location of shot point outside model *** - a shot point is located outside the model.
*** error in specification of amin or amax *** - values of amin or amax have not been specified or are greater than 180 in absolute value.
*** max reflecting boundaries exceeded *** - the number of reflecting boundaries in nrbnd is greater than that allowed for one or more ray groups.
*** max converting boundaries exceeded *** - the number of converting boundaries in ncbnd is greater than that allowed for one or more ray groups.
*** reflect boundary greater than # of layers *** - a boundary in rbnd is greater than or equal to the number of model layers.
*** no ray codes specified *** - no ray codes have been specified in the array ray.
*** shot# _ ray code _ no rays traced *** - the search mode was unable to find rays for the shot point and ray code specified.
*** shot# _ ray code _ 1 ray traced *** - the search mode was unable to find the maximum take-off angle of a refracted ray group for the shot point and ray code specified; only a single ray with a take-off angle equal to the minimum value is traced.
*** less than nray rays traced for _ ray groups *** - the search mode was unable to find rays (or traced less than nray rays) for the number of ray groups specified.
*** possible inaccuracies in rngkta *** - the Runge Kutta routine has detected possible inaccuracies in its attempt to solve the ray tracing equations. The exact point(s) at which the problem occurred can be found in the file r2.out if idump=1 is used. The problem can be eliminated by either reducing the velocity gradient in the appropriate location of the model or reducing the value of step and/or smin. Note that this warning is conservative so that no significant inaccuracies may have occurred.
*** ray stopped - consists of too many points *** - a ray is composed of more than the maximum number of points (step lengths) allowed. Tracing of this ray is terminated.
*** ray stopped - illegal reflection *** - a ray has reflected off a boundary not specified in ray or rbnd and istop=1. Tracing of this ray is terminated.
*** ray stopped - converted ray cannot reflect/refract *** - a ray is at a point of conversion from S to P and is beyond the critical angle. Tracing of this ray is terminated.
*** ray stopped - s-wave cannot propagate *** - a ray propagating as an S-wave has entered a model block in which the S-wave velocity is zero. Tracing of this ray is terminated.
*** ray stopped - reflected from pinchout *** - the layer from which a ray is to be reflected has zero thickness. Tracing of this ray is terminated.
*** block undetermined *** - this is the most serious error since it implies that RAYINVR has lost track of what model block a ray is supposed to be in and therefore implies there is probably a bug in the code. The problem may be avoided if the ray step length is reduced. Also check that layer boundaries do not cross or a deeper boundary is specified before a shallower boundary in the file r.in or v.in. Also check that a source is not located exactly on a layer or block boundary or the edge of the model.
*** max number of rays reaching surface exceeded *** - the maximum allowable number of rays reaching the surface (not including those traced in the search mode) has been reached.
*** no parameters varied for inversion *** - invr=1 but no model parameters have been selected for inversion in the file r.in or v.in.
*** too many parameters varied for inversion *** - the maximum allowable number of model parameters selected for inversion has been exceeded.
*** attempt to interpolate over ximax *** - invr=1 and the travel time and partial derivatives were to be interpolated to an observed receiver location using two rays that have end points greater than ximax from the receiver location; no interpolation is performed. This message is included in the file r1.out at the end of each ray group in which this occurs at least once.
Input file: vm.in contains program input parameters in the PLTPAR, AXEPAR and MODPAR namelists
Input file: v.in contains the velocity model used as input by RAYINVR
Output file: v.out contains the velocity model after it has been edited or smoothed or nodes have been sorted from left to right
Output file: vm.out contains warning and error messages regarding the format of the file v.in as well as summary information
Output file: m.out contains the two-way travel times of model boundaries and RMS velocity profile corresponding to the plots generated by VMODEL
Output file: p.out contains all plot commands for the run used as input by the program RAYPLOT
1) Plotting parameters (PLTPAR namelist):
iplot - generate the plot during the run (1), or write all plot commands to the file p.out (0), or do both (2) (default: 1)
imod - plot the 2-D model as distance versus depth or two-way travel time (default: 0)
idash - plot model boundaries as dashed lines (default: 1)
ivel - plot the velocity values (km/s) at their appropriate locations within model (default: 0)
ivp - plot 1-D velocity profiles versus depth or two-way travel time; the velocity profiles are written to the file vm.out (default: 0)
izort - plot the 1-D velocity profiles and 2-D model versus two-way travel time; if izort=0, they are plotted versus depth (default: 0)
ivrms - plot the RMS velocity of the model versus distance; the RMS velocity profile is written to the file m.out if idump=1 (default: 0)
idump - write the two-way travel times of model boundaries and the RMS velocity profile as plotted to the file m.out (default: 0)
ifrefl - plot floating reflectors from the file f.in in the 2-D model (default: 0)
velht - the height of the velocity values (mm) when ivel=1 is equal to velht*albht (default: 0.7)
xtinc - the spacing (km) of points at which the two-way travel time of model boundaries is calculated if imod=1 and izort=1 (default: (xmax-xmin)/100)
ntsmth - number of applications of a 3-point averaging filter to the model boundaries when plotted versus two-way travel time (default: 0)
xvp - an array containing the x-coordinates (km) at which 1-D velocity profiles are plotted if ivp=1 (default: (xmin+xmax)/2, for the first element only)
vrmstl, vrmsbl - the top and bottom layer, respectively, over which the RMS velocity of the model is calculated if ivrms=1 (default: 1, number of model layers)
xrinc - the spacing (km) of points at which the RMS velocity is calculated (default: (xmax-xmin)/100)
nrsmth - number of applications of a 3-point averaging filter to the RMS velocity versus distance profile (default: 0)
ibcol, ifcol - background and foreground colours (defaults: 0, 1)
2) Axes parameters (AXEPAR namelist):
iaxlab - plot axes labels (default: 1)
albht - height of axes labels (mm) (default: 0.2)
xmin, xmax - minimum and maximum distance (km) of velocity model
xmm - length of distance axis (mm)
xtmin, xtmax - minimum and maximum values (km) of tick marks
ntickx - number of intervals separated by tick marks along distance axis
ndecix - number of digits after decimal in distance axis annotation; -1 for integer annotation (defaults: 0, none, 250; values for xtmin, xtmax, ntickx and ndecix depend on values of xmin and xmax)
zmin, zmax - minimum and maximum depth (km) of velocity model
zmm - length of depth axis (mm)
ztmin, ztmax - minimum and maximum values (km) of tick marks
ntickz - number of intervals separated by tick marks along depth axis
ndeciz - number of digits after decimal in depth axis annotation; -1 for integer annotation (defaults: 0, 50, 75; values for ztmin, ztmax, ntickz and ndeciz depend on values of zmin and zmax)
tmin, tmax - minimum and maximum two-way travel time (s) of 1-D velocity profiles or 2-D model boundary plots
tmm - length of time axis (mm)
ttmin, ttmax - minimum and maximum values (s) of tick marks
ntickt - number of intervals separated by tick marks along time axis
ndecit - number of digits after decimal in time axis annotation; -1 for integer annotation (defaults: 0, 10, 75; values for ttmin, ttmax, ntickt and ndecit depend on values of tmin and tmax)
vmin, vmax - minimum and maximum velocity (km/s) of 1-D velocity profiles
vmm - length of velocity axis (mm)
vtmin, vtmax - minimum and maximum values (km/s) of tick marks
ntickv - number of intervals separated by tick marks along velocity axis
ndeciv - number of digits after decimal in velocity axis annotation; -1 for integer annotation (defaults: 0, 8, 75, values for vtmin, vtmax, ntickv and ndeciv depend on values of vmin and vmax)
vrmin, vrmax - minimum and maximum velocity (km/s) of RMS velocity profile
vrmm - length of RMS velocity axis (mm)
vrtmin, vrtmax - minimum and maximum values (km/s) of tick marks
ntckvr - number of intervals separated by tick marks along RMS velocity axis
ndecir - number of digits after decimal in RMS velocity axis annotation; -1 for integer annotation (defaults: 2, 7, 75, values for vrtmin, vrtmax, ntckvr and ndecir depend on values of vrmin and vrmax)
iorder - re-order all boundary and velocity nodes from left to right; if iorder=0, a message is written to the screen and the file vm.out to indicate the locations where boundaries or velocities are not listed left to right (default: 0)
izint - an array containing the layer boundaries to be re-sampled to increase or decrease the number of boundary nodes
ivuint, ivlint - an array containing the layers in which the upper and lower velocity values are to be re-sampled, respectively, to increase or decrease the number of velocity points
iswit - when interpolating the boundaries and velocities using izint, ivuint and ivlint, the corresponding switches equal to 0, 1 or -1 (see lines c, f and i in the description of the file r.in for the program RAYINVR) will be set equal to 1 if either of the switches across which the interpolation is performed is equal to 1 and it will be set equal to -1 if the two switches equal 0 and -1; if iswit=0, the corresponding switch will be set equal to 0 if the switches across which the interpolation is performed are different (default: 1)
izsmt - an array containing the layer boundaries to be smoothed using a three-point averaging filter
ivusmt, ivlsmt - an array containing the layers in which the upper and lower velocity values are to be smoothed, respectively, using a three-point averaging filter; smoothing is performed laterally on the upper and lower velocities separately.
nzint - an array containing the number of points at which to uniformly re-sample the layer boundaries specified in the array izint; if nzint=1, the average boundary depth is calculated; if nzint equals the current number of boundary nodes, no re-sampling is performed (default: none; however, the default is the first element of nzint for all layer boundaries if only one value is specified)
nvuint, nvlint - an array containing the number of points at which to uniformly re-sample the upper and lower layer velocities specified in the arrays ivuint and ivlint, respectively; if nvuint=1 or nvlint=1, the average upper or lower layer velocity is calculated; if nvuint or nvlint equals the current number of upper or lower velocity points, no re-sampling is performed (default: none; however, the default is the first element of nvuint and nvlint for all layers if only one value is specified)
nzsmt - an array containing the number of applications of a three-point averaging filter to the layer boundaries specified in the array izsmt (default: 1; however, the default is the first element of nzsmt for all layer boundaries if only one value is specified)
nvusmt, nvlsmt - an array containing the number of applications of a three-point averaging filter to the upper and lower layer velocities specified in the arrays ivusmt and ivlsmt, respectively (default: 1; however, the default is the first element of nvusmt and nvlsmt for all layers if only one value is specified)
velmin, velmax - write a message to the screen and the file vm.out indicating the location and value of velocities less than or greater than velmin and velmax, respectively (defaults: 0.1, 7)
dsmax - write a message to the screen and the file vm.out indicating the location and value of slope changes between three successive boundary nodes greater than dsmax (degrees), (default: 10)
dvvmax, dlvmax - write a message to the screen and the file vm.out indicating the location and value of vertical velocity gradients greater than dvvmax (s-1) and lateral velocity gradients greater than dlvmax (s-1), (defaults: 1.0, 0.1)
Low-velocity zones and pinchouts: low-velocity zones that occur across one or more layers that have been pinched out will not be detected.
External plot routines: VMODEL is self-contained except for the graphics calls inside the following CALCOMP or CALCOMP-like plot routines: PLOTS, PLOT, NUMBER, SYMBOL, LINE, EMPTY, ERASE, PLOTND. The file pltlib.f contains ALL these routines (and a few other less important ones used by the graphics system where the code was developed) and it will be necessary to replace the "call" statements within each of these with their equivalents in the local graphics package.
model layers - player
points defining a single layer boundary (must be a multiple of 10) - ppcntr
points at which the upper or lower layer velocity is defined (must be a multiple of 10) - ppvel
1-D velocity profiles - pnvp
points defining layer boundary versus two-way travel time or RMS velocity profile - ppnpts
*** xmax not specified *** - the value of xmax must be specified in the AXEPAR namelist.
*** xmin not specified *** - the value of xmin is needed and must be specified in the AXEPAR namelist since it cannot be determined from the file v.in.
*** a value of nzint > ppcntr *** - all values in the array nzint must be less than or equal to the value of ppcntr specified in the file vmodel.par.
*** a value of nvuint > ppvel *** - all values in the array nvuint must be less than or equal to the value of ppvel specified in the file vmodel.par.
*** a value of nvlint > ppvel *** - all values in the array nvlint must be less than or equal to the value of ppvel specified in the file vmodel.par.
*** v.in has incorrect number of lines *** - the number of lines in the file v.in is not a multiple of three as it should be.
*** no node specified at xmax for boundary _ *** - the last (or only) node of boundary _ must be specified at xmax.
*** no upper vel specified at xmax for layer _ *** - the last (or only) upper velocity value of layer _ must be specified at xmax.
*** no lower vel specified at xmax for layer _ *** - the last (or only) lower velocity value of layer _ must be specified at xmax.
*** first node not specified at xmin for boundary _ *** - the first node of boundary _ must be specified at xmin.
*** first upper vel not specified at xmin for layer _ *** - the first upper velocity value of layer _ must be specified at xmin.
*** first lower vel not specified at xmin for layer _ *** - the first lower velocity value of layer _ must be specified at xmin.
*** single node not specified at xmax for boundary _ *** - the single node of boundary _ must be specified at xmax.
*** single upper vel not specified at xmax for layer _ *** - the single upper velocity of layer _ must be specified at xmax.
*** single lower vel not specified at xmax for layer _ *** - the single lower velocity of layer _ must be specified at xmax.
*** nodes not specified left to right at _ km for boundary _ *** - the nodes of boundary _ are not listed left to right at _ km.
*** upper vel not specified left to right at _ km for layer _ *** - the upper velocities of layer _ are not listed left to right at _ km.
*** lower vel not specified left to right at _ km for layer _ *** - the lower velocities of layer _ are not listed left to right at _ km.
*** check for incorrect xmax *** - the value of xmax specified in the AXEPAR namelist is probably incorrect since the final node or velocity value does not equal xmax at least twice.
*** unequal # of bnd nodes for layer _ *** - the number of upper and lower boundary nodes for layer _ must be equal since its thickness is fixed at one or more points.
*** unequal # of vel nodes in layer _ *** - the number of upper and lower velocity nodes for layer _ must be equal since the vertical velocity gradient is fixed at one or more points.
*** different bnd node positions for layer _ *** - the x-coordinates of upper and lower boundary nodes for layer _ must be equal since its thickness is fixed at one or more points.
*** different vel node positions for layer _ *** - the x-coordinates of upper and lower velocities for layer _ must be equal since its vertical velocity gradient is fixed at one or more points.
*** check gradient in layer _ *** - the vertical velocity gradient is fixed in a layer which contains a pinchout, the updated lower velocity values should be checked after re-sampling, smoothing or inverting these parameters.
*** zero velocity at top of model *** - the upper layer velocity in the top model layer cannot be equal to zero.
*** boundary _ is above boundary _ *** - the first layer boundary is positioned above the second boundary, although it is listed below it in the file v.in.
*** boundary _ crosses boundary _ at _ km *** - the first layer boundary crosses the second boundary at _ km.
*** premature end of file *** - an end-of-file has been reached before it was expected in the file v.in, probably because of an insufficient number of lines (i.e., the file is incomplete) or the values of player, ppcntr and/or ppvel in the file vmodel.par (and rayinvr.par) are insufficient for the current problem (see section on array sizes).
Input file: d.in contains program input parameters in the DMPPAR namelist
Input file: i.out is the output file generated by RAYINVR
Input/Output file: v.in is the input file used by RAYINVR if imodf=1 (in the TRAPAR namelist in r.in). It is overwritten with the updated velocity model after applying the inversion.
Output file: d.out contains the model parameter adjustments and corresponding resolution and error estimates as well as the updated velocity model
DMPPAR namelist:
dmpfct - an overall damping factor to control the trade-off between resolution and variance (default: 1.0)
velunc - an estimate of the uncertainty (square root of the variance) of the model velocity values (km/s) (default: 0.1; however, if velunc is equal to zero, the uncertainties listed in the file i.out are used)
bndunc - an estimate of the uncertainty (square root of the variance) of the depth of model boundary values (km) (default: 0.1; however, if bndunc is equal to zero, the uncertainties listed in the file i.out are used)
xmax - maximum distance (km) of velocity model (default: none)
Run only once: after running RAYINVR, you can not change the v.in file in anyway if you intend to run DMPLSTSQR afterwards. And you must not run DMPLSTSQR more than once without first running RAYINVR again, otherwise twice the model perturbation will be added to the current model.
Specifying model uncertainties: the main purpose of this is as a weighting to account for the difference in magnitude of velocity and depth of boundary values and thereby equalize their relative importance during the inversion. If different uncertainties are required for specific boundary or velocity nodes, the file i.out is edited to incorporate the appropriate uncertainties and the values of velunc and/or bndunc are set equal to zero.
Fixed vertical velocity gradient: if the vertical velocity gradient is fixed in a layer which contains a pinchout, there may be problems in determining the updated lower layer velocities in a few special cases. A warning is given and these parameters should be checked after the inversion.
Inversion of layer pinchouts: in a few special cases there are bugs in the inversion code when attempting to invert model parameters associated with a layer pinchout; check these parameters after the inversion.
Input file: v2.in is the input file v.in containing the velocity model used by RAYINVR
Output file: vdiff.out contains the difference between the files v2.and v1.in; it has the same x-coordinates as v1.in and v2.in, but the difference of the v2.in values minus the v1.in values for each boundary depth and velocity
The value of xmax is input interactively. The main purpose of VDIFF is to allow the resolution of a final model to be tested by observing how the perturbation of a single model parameter is "smeared" into adjacent parameters. To do this, the difference between the original final model and the final model obtained after inverting the data generated by the final model with a single parameter perturbation is taken. VDIFF may also be used to compare a final model with the true model in a synthetic test.
Output file: tx.out contains the those travel times from the file tx.in that satisfy the specified shot gap and spread lengths
The shot gap and left and right spread length (km) are input interactively.
The input and output is interactive in which the chi-squared value and corresponding number of observations used in the inversion are supplied for the two models. The probability of significantly different models is given as well as a statement of whether the models are significantly different at a 5% significance level.
Input file: rec.in contains the irregularly spaced seismogram locations at which the travel times are to be interpolated; format is F10.3 if the same receiver locations are to be used for each shot, and format is the same as tx.in (see description under RAYINVR) if different receiver locations are required for each shot, the x-coordinates of the travel times being the seismogram locations.
Output file: tx.out contains the interpolated travel times in the same format as tx.in
For a uniform seismogram spacing, the minimum and maximum seismogram location and spacing (km) are input interactively. If a non-uniform spacing is required, the seismogram locations in the file rec.in are used. Note that if the file tx.in corresponding to a set of observed travel time picks is used for rec.in, a set of calculated travel times may be generated at the same station locations (and assigned the same associated pick uncertainty) as the observed data, as is needed when estimating a final model's spatial resolution using the technique described under VDIFF.
Output file: tx.out contains the travel times with noise added in the same format as tx.in
A seed for the random number generator is input interactively. The standard deviation of the noise added to each pick is equal to the uncertainty for that pick in the tx.in file.
Input file: i2.in is the output file i.out generated by RAYINVR
Output file: i.out contains the combined information in the files i1.in and i2.in in the same format for use as input to the program DMPLSTSQR
The files i1.in and i2.in must have been generated by RAYINVR using the same velocity model with the same parameters selected for inversion in both runs. COMBINE may be used if, for example, the rays from two or more shots are traced in separate runs of RAYINVR. Note, COMBINE should not be used if partial derivatives for the same travel time picks have been calculated in both of the separate runs since two ray paths may be used in the inversion corresponding to a single travel time pick, instead of the ray path with minimum travel time.
Input file: p.in contains the (x,y) coordinates (mm) of the origins of each plot if multiple plot panels are to be placed in a single plot frame; each (x,y) pair is contained on a separate line in free-format.
External plot routines: RAYPLOT is self-contained except for the graphics calls inside the following CALCOMP or CALCOMP-like plot routines: PLOTS, PLOT, NUMBER, SYMBOL, LINE, EMPTY, ERASE, PLOTND. The file pltlib.f contains ALL these routines (and a few other less important ones used by the graphics system where the code was developed) and it will be necessary to replace the "call" statements within each of these with their equivalents in the local graphics package.
A "plot" here constitutes the graphics that occurs between successive erasures of the screen when running any of the graphics programs. Therefore, each screen erasure is replaced by a resetting of the plot origin according to the coordinates in the file p.in. Thus, for example, the ray or traveltime diagrams for each shot may be organized into a single plot frame, but each in its separate box, if isep>0.
Another purpose of RAYPLOT is for generating a minimum-traveltime raypath diagram when using RAYINVR with i2pt>0. After running RAYINVR with i2pt>0 and iplot=0 or 2, run the program 2pt. The program 2pt produces a bit mask file which will force only the minimum traveltime raypths to bg plotted with RAYPLOT. Note the purpose of this is only for the case in which more than one ray group has the same corresponding value of ivray when running RAYINVR so that it is possible for multiple raypaths to be traced to a single receiver when using i2pt>0. By plotting only the minimum-traveltime raypaths, only the raypaths actually used in the inversion are displayed, and hence an exact illustration of the model coverage is obtained.
Other interactive input is for the parameters iroute and iseg which are only needed for users with uniras graphics.
See .../sol2src/zelt/rayinvr/misc/