叠前逆时偏移技术在隐伏断裂勘察中的应用

Application of the Pre-stack Reverse Time Migration in Active Fault Survey

为了解决高速铁路工程建设场所地下隐伏活动断裂埋藏较深、结构复杂、具体断点位置难以确定等技术难题,拟开展地震反射波逆时偏移技术研究,建立叠前地震反射资料去噪、层析速度建模、逆时偏移成像处理流程,并分析探讨逆时偏移技术应用效果。以某高铁夏垫地区为试验场地,对所述逆时偏移技术进行实际应用及验证,研究表明,成像结果对断点位置刻画准确,同时对地层完整性有一定反映。主要得到以下结论:(1)地震逆时偏移技术基于双程波动方程,没有倾角和横向变速限制,理论上能够解决复杂地质构造成像问题,并为工程地质解译提供准确的深度域成像结果;(2)相较于传统叠加剖面法,逆时偏移技术断层归位准确、断面清晰、地层接触关系更加清楚,对基岩成像质量有一定改善,且振幅的保真度相对较高。

The underground concealed active faults in the high-speed railway construction plants are relatively deep,and it is difficult to determine the location of the specific fault points.Thus,this paper intended to conduct the seismic reflection reverse time migration(RTM)technique and established the seismic data denoising,tomographic velocity modeling,and reverse time migration imaging processing.The underground fault structure in the area were described finely and the application effect of reverse time migration was discussed which help provide technical guidance for similar site surveys.In this paper,the Xiadian area of one high-speed railway was taken as the test site,the RTM was applied and verified.The imaging results could accurately describe the location of fault points and reflect the formation integrity to some extent.Through the research,it is concluded that(1)The seismic reverse-time migration technology is based on the two-way wave equation and has no inclination and lateral velocity change limitation.In theory,RTM can solve complex geological structures􀆳imaging problems and provide accurate depth-domain imaging results for engineering geological interpretation.(2)Application in Xiadian shows that the reverse time migration result has accurate fault homing,apparent cross-sections,clearer stratigraphic contact relationships,improved bedrock imaging,and relatively high amplitude fidelity compared with the traditional post-stack profile.