anchor.diff:        p = y*cd + d*sd
         q = y*sd - d*cd
   
  -      eta(1) = p+wid/2.0d0
  -      eta(2) = p-wid/2.0d0
  +      eta(1) = p+wid*0.5d0
  +      eta(2) = p-wid*0.5d0
   C      eta(1) = p
   C      eta(2) = p-wid
         if (dabs(eta(1)).lt.eps) eta(1) = zro
  
positive.code:       strain(1,1) = uxx
        strain(2,2) = uyy
        strain(3,3) = uzz
        strain(1,2) = (uxy+uyx)/2.0d0
        strain(1,3) = (uxz+uzx)/2.0d0
        strain(2,3) = (uyz+uzy)/2.0d0
        strain(2,1) = strain(1,2)
        strain(3,1) = strain(1,3)
        strain(3,2) = strain(2,3)
  
negative.code: C----
  C Coordinates on fault plane (x,p,q) and distance from edges (ksi,eta)
  C----
        ksi(1) = x+len*0.5d0
        ksi(2) = x-len*0.5d0
  C      ksi(1) = x
  C      ksi(2) = x-len
        if (dabs(ksi(1)).lt.eps) ksi(1) = zro
  