.clr file format

Definition of Layers

A single layer is defined by a block of lines with layer-Keywords. Since a layer consists of up to six different physical parameters and a depth range, some means to group these informations into a layer is necessary. For this purpose, the start and end modifiers of the layer keyword have been introduced.

A full-featured layer definition then looks like this:

!layer !start LayerName
!layer !depth p1 p2
!layer !vp p1 p2 p3 ... pn
!layer !vs p1 p2 p3 ... pn
!layer !rho p1 p2 p3 ... pn
!layer !qp p1 p2 p3 ... pn
!layer !qs p1 p2 p3 ... pn
!layer !end

Where the pn are the coefficients of the respective layer polynomials. (Except for the !depth declaration, where p1 and p2 give the top and bottom depth of the layer. min(p1 p2) is the top depth, max(p1 p2) the bottom depth)

Instead of a definition by depths measured from the surface, the vertical extent of the layer may also be defined by two radius values, measured from the planet's center.

Different layers may use different vertical coordinates: it is possible to define one layer in terms of depth and another one in terms of radius. It is even possible to define one parameter of the same layer by depth and another by radius: the modifier is effective in its own line only.

If one of the parameters is not defined in the model (IASP91, for example, does not define densities and quality factors), simply omit the respective line. Undefined parameters will result in NaN output of the reading routine.

The definition of the IASP91 transition zone, for example, may look like this:

!layer !start Transition Zone
!layer !vp    29.38896 -21.40656
!layer !vs    17.70732 -13.50652
!layer !depth 410 660
!layer !end

NOTE that, although the layer is named "Transition Zone", this layer definition does not imply a definition of discontinuities at 410km and 660km depth! There will be discontinuities at these depths at which rays are refracted, but a program will not be able to recognize these discontinuities as those delimiting the transition zone. This requires extra definitions of discontinuities.

If there are multiple lines in a layer definition block which define the same quantity, the last one of them will overwrite all previous ones.


eof.