The Seismic Imaging Of Irregular Surface In Southwestern Fujian

The traditional mining exploration method has not met the needs for modern exploration task. Seismic method is a new breakthrough in mining exploration methods, because of its probing depth, high resolution, accurate and reliable detection result. Currently, with advances of energy seismic exploration technology, exploration equipment developing, the level of data acquisition, processing and interpretation is raising, which makes the metal ore seismic exploration possible.The metal ore is relative to magmatic activity, its controlling structure is complicated and its distribution does not meet the hypothesis of layered strata. The seismic data are not easy to be obtained. The main terrain of metal mines in southwestern Fujian is mountains and hills, both surface and subsurface geological conditions are complex. In these area, the seismic wave’s energy is weak, signal to noise ratio and resolution capability are low. The routine seismic processing is difficult to obtain clear information about subsurface structure. Meanwhile, the Dapai iron ore in southwestern Fujian are shallow, it requires more sophisticated near-surface treatment.In order to solve the seismic processing problems of metal ore seismic date in southwestern Fujian, the writer combines irregular superficial depth migration technique and Tomographic inversion technique. After model tests and real seismic data tests, the writer comes up with the real surface treatment method which can be applied to the “double complex” area.The thesis introduces the theory of tomographic inversion and pre-stack depth migration. Firstly, I make SEG model test and analyze the optimal tomographic inversion parameter, like calculated depth, meshing size, initial velocity model and so on. Secondly, I make pre-stack depth migration from irregular surface by using the optimal velocity model which obtain from tomographic inversion, and compare with the traditional migration results. Finally, I complete the migrate imaging of the seismic data in southwestern Fujian.The research shows that tomographic inversion are not restrained by the changes of surface and near-surface structure in horizontal and vertical direction. It can obtain more precise near-surface information. Pre-stack depth migration technology enables the homing of diffraction point and the accurate superposition of common reflection point. It can fix subsurface image distortion which is caused by steep dip strata and speed variations. In “double complex” area, by combining tomographic inversion and pre-stack depth migration technology and by making migrate imaging directly from irregular surface, it can reduce the effect of complex surface and subsurface structure conditions and makes the shallow information show more details.