初至波地震层析成像中自动生成初始速度模型的方法研究

摘要

The initial velocity model is primary given in first-arrival seismic tomography,the quality of tomography inver-sion,convergence and convergence speed are effected mostly by the initial velocity model.An automatically building initial ve-locity model using first-arrivals has been proposed with near-surface velocity fields tomographic inversion in the paper.As-suming that the first-arrivals are consist of the direct waves and refraction waves,then the initial velocity model is directly cal-culated by refraction method,which can be realized automatically by program without factitious interfere.The method is ap-plied to the theory model and actual data,then the iterative tomography technique is applied to obtain actual velocity model based on the initial velocity model.The results show that the method is effective with quickly convergence,and the inversion results are consist with real velocity model.%初至波地震层析成像需要给定初始速度模型，给定的初始速度模型很大程度上影响层析反演的质量、反演是否收敛和收敛速度的快慢。使用层析成像反演近地表速度场时，这里提出了一种利用大炮初至时间自动生成初始速度模型的方法。假定大炮初至是由直达波和折射波构成的，然后用折射波法直接求取初始速度模型，该方法生成的初始速度模型可直接由程序自动实现，无需人为干扰。将该方法应用在理论模型和实际资料中，由此产生的初始速度模型采用层析成像技术进行迭代反演，结果表明，该方法建立的初始模型加快了反演收敛速度，反演结果和真实速度模型基本一致。