rayinvr.doc

实现地震射线追踪和反演的frotran程序

   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.

                           Array Sizes

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

                                      
                    Warning and Error Messages

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:
      (1) the  x-coordinates  of a  boundary  or upper  or  lower 
         velocity have not been listed from left to right
      (2) the  x-coordinate  of the  first  or last  point  of  a 
         boundary or upper or lower velocity (comprised of two or 
         more points) does not equal xmin or xmax, respectively
      (3) a model block has a P-wave velocity less than or equal 
         to zero
      (4) a line  specifying the  model (x-  or z-coordinates or  
         upper  or  lower  velocity   or  flags  indicating  the   
         parameters to be  varied during  the inversion)  in the  
         file r.in or v.in  has been omitted  (i.e., the file is  
         incomplete)
      (5) the x-coordinates of the upper layer velocities do not  
         equal the x-coordinates of the lower layer velocities in 
         a layer in which  the vertical velocity  gradient is to  
         remain fixed during the inversion
      (6) the x-coordinates of  the upper layer  boundary do not  
         equal the x-coordinates of the lower layer boundary in a 
         layer in which the thickness  is to remain fixed during  
         the inversion

*** 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.

                          Other Programs

VMODEL: a program to check, edit  and plot the file v.in used  as 
        input by the program RAYINVR

                        Program Description
  
  The program VMODEL  performs three main  tasks associated with  
the file v.in containing the velocity model used as input  by the 
program RAYINVR. First, it checks the format of v.in to ensure it 
is as  required  by RAYINVR.  If  it  detects format  errors,  it 
indicates the location  and type of  error. Similarly, it  checks 
for unusually small or  large velocity values, negative  vertical 
velocity gradients, large vertical or lateral velocity gradients, 
low-velocity zones, crossing layer boundaries, and boundaries with 
large slope changes. Second, VMODEL can edit the file v.in by (1) 
re-ordering the boundary and/or velocity nodes from left to right, 
(2) re-sampling the boundary and/or velocity nodes to increase or 
decrease the number  of model parameters,  and (3) smoothing  the 
boundaries and/or lateral velocity variations using a three-point 
averaging filter. Third, plot (1)  the 2-D model versus depth  or 
two-way travel time,  (2) 1-D velocity  profiles versus depth  or 
time, or (3) the RMS velocity variation across the model.
  
                              Files

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