**
**Accuracy evaluation of
typical, infinite bandwidth, minimum time seismic
modeling schemes

**I. F. Louis, K. D. Marmarinos and F. I. Louis**

Department of Geophysics and Geothermics, Faculty of Geology
and GeoEnvironment, University of Athens,

Panepistimiopolis, Ilissia, Athens 15784, Greece

**
****Abstract:*** **
The performance of a variety of travel time
modelling schemes is evaluated, in terms of their
accuracy, by using numerical simulations. The methods considered predict
minimum travel times in two-dimensional P-wave velocity model
parameterizations. They are typical, infinite
bandwidth, seismic modeling schemes implemented in many inversion
and imaging algorithms The methods considered include: the finite
differencing approach of the eikonal equation as
described by Vidale, the shortest path method as described by
Moser and a variation of it as described by Nakanishi and Yamaguchi for
calculation of seismic rays and first arrivals, and
the two-point ray tracing technique as presented by
Vesnaver. Quantitative comparisons between forward modeling approaches are based
on the misfit between true and calculated travel
times, number of model parameters used and the
smoothness of the velocity field. When the constant velocity distribution is
utilized Vidale’s method is giving results within
tolerance with respect to travel time accuracy in
opposition to the ray perturbation and SPM scheme where the error is lower. For
fine model parameterizations, Vidale’s scheme remains
the most efficient in computer time but still suffers
in the error distribution. In stratified models, Vidale’s scheme gives
increasing errors for increasing velocity contrast. In
smooth velocity fields a drop in the misfit is
observed in the far field and the method is still computationally faster.
Shortest path calculations are independent from the
model whereas the error remains related to the number
of possible routes. The two-point raytracing scheme performs better in smooth
velocity fields giving time misfits strongly associated with the distance
and smoothly decreasing for far offsets.*