anchor.diff:                    ktrg = 2
                 endif
             elseif (tag(1:5).eq.'-disp') then
  -              if (kdsp.eq.0) kdsp = 1
  +              if (kdsp.eq.0) then
  +                  kdsp = 1
  +              elseif (kdsp.eq.-1) then
  +                  kdsp = 2
  +              endif
                 i = i + 1
                 call getarg(i,dspf)
             elseif (tag(1:3).eq.'-az') then
  -              kdsp = 2
  +              if (kdsp.eq.1) then
  +                  kdsp = 2
  +              else
  +                  kdsp = -1
  +              endif
             elseif (tag(1:7).eq.'-strain') then
                 kstn = 1
                 i = i + 1
  
positive.code:      1                          + dcos(str-pi/2.0d0)*dsin(rak)*dcos(dip)
        r(3) =                                         dsin(rak)*dsin(dip)
  C Project shear component on slip vector
        shear = s(1)*r(1) + s(2)*r(2) + s(3)*r(3)
  C Coulomb stress (recall sign convention: pos = dilation)
        coul = shear + frc*norml
        RETURN
  
negative.code:       REAL*8 coul,norml,shear,stress(3,3),frc
        REAL*8 strin,dipin,rakin,str,dip,rak,n(3),trac(3),r(3),s(3)
        INTEGER i
        INTEGER kdsp,kstn,ksts,knor,kshr,kcou,kgmt
        COMMON /OCHECK/ kdsp,kstn,ksts,knor,kshr,kcou,kgmt
        str = strin*d2r
        dip = dipin*d2r
        rak = rakin*d2r
  