## Finite differences above the MODEL package

**Vaclav Bucha** ** & **
**Ludek Klimes**
### Summary

Fortran code for 2-D P-SV elastic second-order finite differences has
been split into program generating gridded "effective" elastic parameters
and the finite-difference program.
Both programs have been modified to read and write data using the
subroutines of package FORMS and are located in program package FD.
This enabled to prepare the interface between package MODEL
and the finite-difference program and to use the programs
of package FORMS to process and display the results
of finite-difference package FD.
The usage of software package FD is illustrated on
two numerical examples.
The differences between 2-D finite-difference seismograms
and 3-D ray-theory seismograms are demonstrated and discussed
in the second example.

### Keywords

Seismic models, elastic waves, synthetic seismograms, finite differences,
ray theory.

### Whole paper

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In: Seismic Waves in Complex 3-D Structures, Report 8,
pp. 171-192, Dep. Geophys., Charles Univ., Prague, 1999.

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