anchor.diff:  C   MODIFIED OCT.  1971
   C
   C * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
  -      COMPLEX X, AX
  -      CHARACTER*6 TITLE
  -C
  -      DIMENSION X( 68), AX(3, 64)
  -      COMMON /EQ/ MFOLD,MA2,TITLE(5),DT, MA , MMA, DF,MX
  +      complex X, AX
  +      character*6 TITLE
  +C
  +      dimension X( 68), AX(3, 64)
  +      common /EQ/ MFOLD,MA2,TITLE(5),DT, MA , MMA, DF,MX
   C
         F1 = .5/DT
         FR = FLOAT(IFR)
  
positive.code: C   MODIFIED PBS AUG. 1971
  C   modified to increase number of layers to 50
  C***********************************************************************
        CHARACTER*6 TITLE,IDNT
        COMPLEX SAVE
        COMPLEX X, AX
  C
        DIMENSION XR(8)
        DIMENSION X(300),AX(3,270),S(70),INV(70)
        COMMON /SOILA/ IDNT(6),BL(51),GL(51),FACT(51),H(51),R(51),BF(51)
        COMMON /EQ/ MFOLD,MA2,TITLE(5),DT, MA , MMA, DF,MX
  C
        FREQ = 0.
        SFX = 0.
        SXX = 0.
  C   TRANSFORM VALUES IN X OR IN AX INTO THE TIME DOMAIN
        DO 24  I = 1,MFOLD
        IF (LS.EQ.0) GO TO 241
        SAVE = X(I)
        X(I) = AX(LS,I)
        AX(LS,I) = SAVE
  
negative.code:       MA2 = MA + 2
        MFOLD = MA2/2
        N = MFOLD + 1
        do 12 I = MFOLD,N
        X(I) = 0.
  C
        do 12 L = 1,3
        if (LL(L).LE.0) go to 12
        AX(L,I) = 0.
     12 continue
        MFOLD = MFOLD + 1
        F2 = .5/DT
        write(6,1000) F1,F2,DT, MA
        FMA = FLOAT(MA)
        MX = (ALOG10(FMA)/ALOG10(2.))-1.
        if (MA.GT.2**(MX+1)) MX=MX+1
        IF(NCUT.LE.MFOLD) go to 15
        NCUT=MFOLD
     15 continue
   1000 format(  20H  FREQUENCIES FROM  F6.2, 3H TO F6.2,14H C/SEC ARE REM
       15HOVED /
       216H NEW TIMESTEP = F5.4/19H NUMBER OF VALUES = I5)
        return
        end
  C*****************************
        subroutine INCR(IFR,X,AX)
  C * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
  C   THIS ROUTINE INCREASES NUMBER OF POINTS IN THE RECORD
  C   BY DECREASING TIMESTEP
  