含煤层地质环境下地震波场的数值模拟

本文对含低速煤层地质环境下弹性波场多波多分量地震资料进行了二维数值模拟研究,对人工边界反射进行了有效处理,频散效应得到了有效的压制,对几种不同激发与观测排列方式下的弹性波资料进行了模型计算与分析。

NUMERICAL SIMULATION OF SEISMIC WAVE-FIELDS UNDER THE GEOLOGICAL BACKGROUND OF COAL SEAM

This paper presents a study of numerical simulation for the elastic wave-fields of multi-wave and multi-component scismic records under the geological background of coal seam. Both the artiflcial boundary reflection and the grid dispersion, which produces in the Fmite-difference calculations, is effectively treated in this paper. The seismic records,which are obtained under different conditions of excited sources (at the free surface and in the lower velocity layer) and observcd methods (at the free surface and in wcll), are simulated and analyzcd. When thc sourcc is placcd in the lower vel0city laycr, both the interference of the phasc-length of selsmic waves and widen amplitudes can be seen from the VSP. records, and the "lighting spot" phenomenon can be also seen from the surface records. It is because there are the characteristics of high velocities in top layer and bottom layer media and the polarities of reflection waves are contrary. When the excited source is placed at the free surface, the "darking spot" phcnomcnon can be found from the seismic records. Meanwhile, the wave-form expansion of seismic wave-field and reflection wave-field in the lower velocity layer is shown in VSP records and surface records because these waves interfcre with cach other, and there is dispersion in the lower velocity layer.Perhaps these charactcristics are some important information which the lower velocity layer presents in these surface records and VSP records. It is worth further research and application.