## Two-point ray tracing and controlled initial-value ray tracing
in 3-D heterogeneous block structures.

**Petr Bulant**
### Summary

It is well known, that even in quite simple
seismic models
we need some
kind of the two-point ray tracer to find all existing two-point rays
for all the receivers. One solution is a sophisticated shooting program,
based on an accurate searching for the subdomains of ray take-off parameters,
where the two-point rays may occur. The subdomains may be found by
a special triangularization
of the 2-D domain of ray take-off parameters.
The two-point rays may be then identified inside the triangles
whose all the three vertices are formed by rays
arriving into a receiver area.

Once the domain of ray take-off parameters is triangularized,
we can use the triangles mentioned above to construct the ray cells
through the model volume, and to interpolate travel times
and other quantities inside the cells, like in the wavefront tracing method.
The described controlled initial-value ray tracing method
is a useful extension of two-point ray tracing programs
based on triangularization, providing interpolated values of
ray-theory travel times and other quantities at dense grids located
in the seismic model.

### Whole expanded abstract

The expanded abstract is available in
PostScript (1885 kB !)
and GZIPped PostScript (177 kB).

Expanded Abstracts of 67th Annual Int. SEG Meeting (Dallas),
pp. 1727-1730, Soc. Exploration Geophysicists, Tulsa, 1997.

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