Interpolation of ray theory traveltimes within ray cells

3-D ray tracing followed by interpolation of the computed quantities amongs t the rays is a powerful tool for the computation of ray theory traveltimes , amplitudes and other quantities at the gridpoints of dense rectangular gr ids. Several methods based on the decomposition of the model volume into ra y cells, and on further interpolation within the individual ray cells, have recently been introduced. We propose bilinear and bicubic interpolation sc hemes, which should be applicable in any modelling method based on interpol ation within ray cells. The bicubic interpolation is designed for traveltim es and the bilinear interpolation for other quantities. The interpolation schemes have been incorporated into a controlled initial- value ray tracing program package. Multivalued ray theory traveltime comput ation in a heterogeneous 3-D model is shown as an example.