Quadratic/linear travel time interpolation of seismic ray-tracing

An improved ray-tracing method called quadratic/linear travel time interpolation (QLTI) was developed based on the linear travel time interpolation (LTI) method given by Asakawa to increase seismic travel time measurement accuracy. In the field near the source point, the travel time of the interpolation point was calculated using quadratic travel time interpolation (QTI), while LTI was used to calculate the travel time far from the source. The method improved the travel time accuracy and reduced the accumulated error by replacing the LTI algorithm by the QTI algorithm in the near field. Thus, the travel time accuracy was increased in the full field (especially in the far field). Comparison of numerical and experimental results shows that the present algorithm is more accurate than the conventional LTI method. This seismic ray-tracing algorithm is also more precise and more suitable for complicated conditions such as large velocity variations.