Crosshole Seismic Tomographic Inversion With Seismic First-break And Reflection Traveltimes

Seismic wave velocity is not only important for processing and explanation of seismicdata, but also its itself is the reaction of underground medium important data structure andlithology. Therefore, how to get precise propagation velocity of seismic wave underground isvery impotant. Crosshole seismic tomographic technique is a powerful tool for inversion ofcrosshole medium speed. Therefore, how to use Crosshole seismic tomographic inversiontechnique precisely get precise propagation velocity of seismic wave underground is one ofthe essential problems all the time.Crosshole seismic tomographic is a inversion method which based on observations ofseismic waves travel to build a model, thus rebuild subsurface structure and parameters. Thisis a nonlinear problems, using only a wave traveltime information is difficult to accuratelyand completely to rebuild the imformation of the underground medium speed. So to make fulluse of limited real data inversion has been a research focus. Primary wave easy to identify,track, and stability is good. But it can only give the formation speed, cannot accurately showthe formation interface morphology, so it can’t meet the requirements of exploration anddevelopment. Reflection wave travel time which has relatively abundant undergroundinformation is sensitive to the formation interface, it can accurately show the speed of depthin underground information. So this paper puts forward crosshole seismic tomographicinversion with seismic first-break and reflection traveltimes, this method can also play theadvantages of first-break and reflected wave, it not only can get accurate formation velocityinvertion, but also can get more accurate formation interface shape, thus provide importantdata and reliable basis for high precision seismic exploration, reservoir and mineral resourcesdevelopment.The proposed of crosshole seismic tomographic inversion with seismic first-break andreflection traveltimes is based on the traveltimes, use unit node of formation as modelparameters, and build iteration joint tomography equations. This problem need to solve twosteps forward and inversion, the forward part of the trip with the improved linear traveltimeinterpolation (LTI) method, the inversion part is with damping LSQR method. Programmingto achieve the LTI and with damping LSQR algorithm. Main research results are as follows:1) Joined the secondary nodes on the boundary In the process of crosshole seismic tomographicinversion, it reduces computing time and improve the calculation precision.2) This paperpresents multi-stage, the traditional LTI is applied to the reflection wave, this make it possibleto have reflection wave tomographic inversion; and build iteration joint tomography equations.3) According to the four groups of theoretical model data and result analysis to verify thereliability and practicability of the method proposed in this paper.