Method And Application Of Tomographic Inversion Of First Break In Surface Model

The paper realized a set of methods for tomographic inversion of seismic first break in surface model aimed at complex surface problem in seismic prospecting. The technique is high resolution inversion using travel time and path of seismic ray for inverting the velocity, structure of medium. Tomographic inversion of first break using direct wave, diving wave, refraction wave and combination of the three has the advantage of having vertical and lateral variable velocity and is suitable for inversion in complex surface model that the velocity can vary arbitrarily. Thesis proved that the method is corrective and effective based on theoretical model and real data disposing.Firstly, the paper analyzed the regularity of propagation and style character of first break in surface model based on the regularity of seismic wave propagation. Furthermore, the paper analyzed the principle and method of seismic ray tracing with shortest path algorithm in networks, and the relevant drawbacks in which and improved measures are also analyzed especially, we improved on and perfected a shortest path ray tracing method with dynamic networks based on the shortest path algorithm. On the one hand, the method is a kind of fast method in speed calculation, and occupies the less memory of computation, on the other hand, this algorithm is regardless of model complexity, and has a higher precision for computation of seismic travel times and ray paths. In the next place, A new objective function of tomographic inversion is established which is based on improved method of shortest path ray tracing with dynamic networks, at the same time, the solution method is deduced at length. Accordingly, we realized tomographic inversion of first break in surface model. By using the theoretical model to test the tomographic inversion of first break, we proved it correctness and feasibility. Finally, the paper processing the real seismic data by applying the method of tomographic inversion of first break travel-time in surface model, acquiring reliable surface speed model. It establishes a favorable foundation in order to solve seismic practical datum static correction, wave function continuation correction on near-surface model, and pre-stack depth migration of complex area.