The procedure to estimate the elastic constants of a homogeneous TI medium from traveltime measurements near one axis of symmetry is the following:

- 1.
- Fit the traveltimes with elliptically anisotropic models, one
model
for each wave type. This gives direct and
*NMO*group slownesses. - 2.
- From the direct and
*NMO*group slownesses, find the corresponding direct and*NMO*phase velocities, using equation (26). - 3.
- From the estimated phase velocities, find the elastic constants
using the equations that correspond to the given recording geometry
[either (22) or (23)]. In the case of
*SH*waves, the estimated phase velocities squared are the same as the corresponding elastic constants.

11/17/1997