Research And Application Of2D Seismic Tomography With First-arrival Travel-time

Research on underground structure has always been an extremely importantfield of basic science in geophysics. Seismic tomography is a method that by useof a large numbers of seismic observation data to inverse the internal structure ofthe study area, and becomes an effective mean in the research field. Through therapid development and effective application of the seismic tomographytechnology, people have a further understanding about the internal structure ofthe earth, and it has played a positive role in promoting the subsequent scientificdevelopment and the use of ecological resources.This paper reviews the development history of tomography, elaborates thedeveloping situation of the tomographic imaging at home and abroad, especiallystudies the first-arrival seismic tomography technology.The first arrival is the seismic wave which starts off from the shot source andreaches the detection point in the first time. It includes the phases of the directwave, refracted wave, diffracted wave and so on. In avoid the defects of thetraditional LTI algorithm, this paper has been taking all-round circulationimproved LTI algorithm. Through the model calculation results it shows that the improved algorithm of LTI can track all ray paths of the first arrival successfully.This method has the advantages of high speed, high accuracy, be able to get theminimum global time, etc. In inversion process, the LSQR algorithm is selectedbecause of its stable, high precision and easily to realize. The model inversionresult is great. At last, applied the first arrival seismic wave tomographicimaging method which based on LTI-LSQR inversion algorithm to a internalstructure’s inversion for a coal seam, the inversion result is in good agreementwith the practical situation, and the achieved a ideal result further shows that themethod is reasonable and practical.