Study On The Near-surface Seismic Waves Tomography Method And Technology

Seismic tomography is a methodology for estimating the Earth's properties. In the seismology community, seismic tomography is just a part of seismic imaging, and usually has a more specific purpose to estimate properties such as propagating velocities of compressional waves (P-wave) and shear waves (S-wave). It is applied to the field of engineering geophysics and environmental geophysics and so on. It is a technique which uses seismic date to invert the material attribute of underground structure and determine the fine structure of the earth interior and regional in-homogeneity. It includes model parameterization, forward modeling calculation, and invert calculation.The paper briefly reviews the development course of the seismic tomography technology, and discusses the method of the first break travel-time tomography Through this method, the paper researches near-surface velocity model building, providing velocity information for further static correction or shallow.This paper is introduce the nonlinear travel time interpolation method, deducing primary algorithm and programming the ray tracing method of nonlinear travel time interpolation method and the SIRT inverssioal gorithm. Proves that the nonlinear travel time interpolation method is more Acculative than the linear travel time interpolation method.and propose the Joint algorithm of LTI- nonlinear travel time interpolation method.On this base, we study and summarize forward-inversion effect and its partial influential factors. And summarizes the factors and scope of the principle of selection in order to achieve greater accuracy of first arrival tomographic inversion and inversion stability purposes.On the base of numerical simulation model, the paper inversion the actual seismic data test, proved that the SIRT method is corrective and useful based on the actual modeling calculating. Then, purpose methods and recommendations to further improve the accuracy of Seismic inversion.