Seismic Slope Tomography With Rugged Terrain

Slope tomography is an effective velocity model-building method using thereflection wave traveltime and the gradient of reflection event, by contrast with theconventional reflection travel-time tomography methods,the main characteristic ofslope tomography is the using of reflection travel-time and its gradient simultaneous,the introducing of gradient of travel-time can also better constrain the modelparameters, reduce the multiplicity and improve the reliability of inversion..However,the current slope tomography is usually carried out based on horizontal earthsurface,while in the actual production work, the ground is often undulating and thevelocity of low velocity layer is different from that of target strata, these factorsdistort the reflection events and bring about adverse impact on the inversion results ofstereotomography. Therefore, the application of slope tomography is researchedunder the condition of rugged terrain,the main reaearch contents and reaults asfollows:(1): A method is proposed in this paper for local event slope picking based onCurvelet transform. Firstly, the Curvelet coefficients are obtained from seismic datausing fast discrete Curvelet transform via Wrapping algorithm. Secondly, the locationand direction of locally coherent reflected events are picked from Curveletcoefficients. And the slopes are finally estimated from the above direction. The testswith both synthetic and field data show that our method has a higher precision thanthe existing slant stack method.(2):Implementments the process of slope tomography algorithm, the automaticpicking of travel-time and its gradient, ray tracing in continuum model, thecomputation of travel-time and its gradient, and joint inversion with travel-time andits gradient.and the inversion results of this method appilied to level terraintheoretical data are analyzed and summarized.(3): The near-surface influence on the inversion result using slope tomographyand migration imaging resuts under the condition of only rugged terrain existence、 rugged terrain and low velocity layer both existence is reasearched and analyzed(4):Statics correction method is applied to the seismic data under the condition ofonly rugged terrain existence、rugged terrain and low velocity layer both existence.the inversion result using slope tomography and migration imaging resuts from theseismic data after statics corrected are analyzed and summarized.(5): Wave equation datum correction method is applied to the seismic data underthe condition of only rugged terrain existence、rugged terrain and low velocity layerboth existence.By contrast with the results from the seismic data after statics corrected,the inversion result using slope tomography and migration imaging resuts from theseismic data after wave equation datum corrected are better,so we had better applyWave equation datum correction method to the rugged terrain seismic data.In this waymore accurate velocity model can be got using slope tomography.