Study On Tomographic Static Correction Method

With the highly integrated to the widespread use of digital seismograph, exploration areas gradually shifted from the eastern part to the western, midwest exploration areas of China is gobi desert , mountain , piedmont which has complicatednear surface , with the low-velocity-layer has cutting horizontal change, and no steady refracting layer. The problem of static correction is one of the keys of the seismic exploration . the theoretical conditions of the traditional static correction is not exist. Tomography is not be dependent on the theoretical conditions, becoming the research heatpoint of static correction.First recalling the history and present situation of tomography in my paper, introduced seismic forward and inversion. The part of seismic forward summary many ways to ray tracing , in order to get the velocity model better, this paper put forward a method about high precision fast ray tracing with multi-retracing. Based on Fermat's Principle, target point is chose one by one from source point, a rectangular net centerd this point is set. Calculating the travel time from net grid to target point, and choosing the shortest time as the time from source to target point, informatin of the net grid is also saved. At last every point in the media possesses a ray to source. The next step is ray retracing. As for every grid at a specifica ray, choose a retracing rectangular net according to tracing radius. Calculating the time between source point, retracing rectangular net grid and receiver. If the time is shorter than old one, the retracing rectangular net grid is used to replace old ray grid. The retracing times is chosen according to calculation precision demand. The calculating speed of ray tracing is also improved when choose center net point as basic point. The concepts of trace radius and ray retracing improve precision with big tracing radius and retracing times. The test of models has proved that the method is effective for first seimic arrival ray tracing.The part of inversion summary many means, and compare the pros and cons, choose the SIRT (Simultanneous Iterative Reconstraction) and achieved with programs. Processing theoretical mode and practical data indicate that the SIRT can get the velocity model well.Finally calculate static correction according to the velocity model which get from our Method, To achieve the high precision static correction in Complex terrain and Complex near-surface...