command summary
---------------

put /sep/dave/fracture on your path.

create name  delz= rho= [ lamda= mu1= (mu2= ) ] or [ velp= vels= (velsh= ) ]

  create a parameter set for rock with thickness : delz , density : rho, 
  either specify lamda , mu1 ( optionally mu2 , default=mu1 ) or
                  velp , vels ( optionally velsh , default = vels )


display name 

  display the stiffness matrix and the group representation .


rotate name1 name2 degx= degy= degz=

  rotate rock 'name1' to create 'name2'  rotations are specified as clockwise
  rotations about the specific axis.


combine name1 name2 name3

  combine two layers ( interleaved ) to create a new rock 'name3'


crack name1 name2 name3 excess=

  horizonally crack rock 'name1' with cracks of type 'name2' to create a rock
 'name3' by adding 'excess % ' of stiffness group 3 from 'name2' to 'name1' 


vcrack name1 name2 name3 excess=

  vertically crack rock 'name1' with cracks of type 'name2' to create a rock
 'name3' by adding 'excess % ' of stiffness group 3 from 'name2' to 'name1' 


laymod21 name1 name2 nx= nz=

  create a layer model of nx horizontal points by nz vertical points 
  one panel for each of the 21 elastic constants divided by density.
  the model is rock 'name1' on the left grading linearly to 'name2' on
  the right.
