观测系统对速度层析成像的影响及其收敛性分析

Effect of configurations on velocity tomography and convergence analysis

地震波速度层析成像广泛应用于工程地质勘探,其技术也日趋成熟.但据研究文献分析,目前对地震波层析成像技术的应用和研究多集中于井-井和井-地-井观测方式,众多文献也指出多角度观测能提高成像分辨率,但较少论述复杂观测系统对层析成像效果的影响,缺乏复杂观测系统对层析成像收敛性的定量研究.在实践中,经常遇到复杂观测条件的层析成像问题,如具有井斜的跨孔探测,具有高程差异的井地探测等,为了分析观测系统对层析成像结果的影响,本文以观测系统的复杂性为研究对象,以数值模拟和工程实践为研究方法,分析复杂观测系统对速度层析成像效果的影响,并通过统计均方根误差(RMSE)分析层析收敛性.数值模拟结果说明观测系统复杂性影响层析成像效果,复杂观测系统成像效果优于井-井和井-地-井观测方式,且层析成像收敛速度快;最后,通过应用复杂观测系统对煤矿采空区进行探测,探测结果说明复杂观测系统取得理想效果,说明复杂观测系统更具有应用价值.

Seismic velocity tomography method has been widely applied for engineering geological exploration around the world. However, based on the literature survey of previous studies, it is found that both application and study about seismic wave tomography technique mainly centered on the hole to hole and the hole-surface-hole configurations. Although some previous results have pointed out that multi-angle observation could improve the imaging resolution, little has been done about the effect of complex observation system on tomography results. In addition, quantitative study on the convergence of tomography under complex observation system has also not been well studied yet. During the course of practical engineering application, tomographic imaging problems under the complicated observation conditions are often encountered, for example, the cross-hole detection with the well inclination as well as the well-site detection with the elevation difference. To investigate the influence of observation condition on tomography results, in the current paper, the complexity of observation system was studied. Furthermore, through the method of numerical simulation and practical engineering, the impact of complex observation systems on the velocity tomography was also analyzed. Moreover, the convergence of tomography was studied by the use of Root Mean Square Error(RMSE) method. To summarize results of current investigation, it is found that according to the numerical simulation results, the observation system does affect the imaging effect. In addition, it is also revealed that the imaging resolution under complex observation system is better than that obtained from the hole to hole and the hole-surface-hole configurations. Furthermore, the speed of imaging convergence is also fast under complex observation system. Finally, the complex observation system was employed to explore the goaf of coal mine. It is disclosed that ideal results could be achieved through the use of complex observation system. As a result, the engineering practice indicates that complex observation system has a promising application potential.