3-D Seismic Computerized Tomography By The First Arrival

The seismic Computerized Tomography is a kind of an important geophysics technology utilizing the known data to get the medium velocity model. Medium information in different depth of the earth can be obtained either by natural earthquake or by artificial earthquake according to different researching purposes and needs. Three techniques for realizing first arrival tomography are seismic first arrivals picking, rays tracing and inverting the media model. This paper proposes a new algorithm of picking up the first arrivals, which is named phase space picking algorithm. By processing field seismic data, the satisfied result is obtained.The method in this paper with respect to seismic ray tracing algorithm was Hyugens Wavefront Tracing algorithm. Although traditional ray methods can trace the multiple-valued traveltime, they lack stability. The finite-difference method has better stability; however, it can only compute the minimum travaltime. Furthermore, HWT algorithm could combine computing the multiple-valued traveltime with the stabiliy.In the field of inverting media velocity model, LSQR was used in field seismic data to check the feasibility of the proposed method. Innovation in this paper includes, presenting the phase space picking algorithm; applying the HWT in the wave reflecting ray tracing.