Tomographic image of curved rays in borehole to borehole seismic survey

Velocity tomographic inversion is performed by using travel times of transmitted waves from one borehole to another and considering curvatures of seismic rays. We take a triangular grid, where velocity and position parameters of each grid-point must be given. Velocity gradient in an element is a constant vector, and the velocity at each position may be calculated by making two-dimensional linear interpolation. Fast hitting target method achieves ray tracing between two points. Sparse ill-conditioned system of equations are solved by doing singular value decomposition (SVD). In this paper, two theoretical models are given. Trial results say the method results in good image and has good applicability