anchor.diff:  C Compute point source isotropic volume change moment
   C----
         IMPLICIT none
  -      REAL*8 pi,d2r
  -      PARAMETER (pi=4.0d0*datan(1.0d0),d2r=pi/1.8d2)
         REAL*8 Mvol,dvol,vp,vs,dens
         REAL*8 mu,lamda
         mu = dens*vs*vs
  
positive.code: 
        IMPLICIT none
        REAL*8 x,y,stdp,evdp,z,c,d             ! Coordinates
        REAL*8 dipin,rakin,area,dvol,Mvol      ! Fault parameters
        REAL*8 vp,vs,dens                      ! Half-space parameters
        INTEGER i,j
        REAL*8 u(6,3),f(6,3),ux,uy,uz
  
negative.code: C----
        IMPLICIT NONE
        REAL*8 x,y,stdp,evdp,z,c,d
        REAL*8 dipin,dvol,Mvol
        REAL*8 vp,vs,dens
        INTEGER i,j
        REAL*8 fx(6,3),fy(6,3),fz(6,3),f(6),ux(6,3),uy(6,3),uz(6,3),u(6)
  