关键词: 活断层, 浅层地震勘探, 数据处理, 速度分析, 参数选取

Abstract: Shallow seismic exploration is the main technique in present urban active faults detecting.The detection precision is not only affected by the factors of sources and receivers,but also closely related to the precision of seismic data processing.Velocity analysis is an important step in seismic data processing,which determines the precision of NMO,CDP stack,post-stack migration and time-depth conversion.Considering the properties of low stack folds,shallow objected layers and big background noise of shallow seismic data,the parameters selection for velocity analysis is studied in the paper.Firstly,by analyzing the offsets of different traces in adjacent CDP gathers,and comparing between single and multiple CDP gathers,the principle of how to extract large CDP gathers is proposed.And then,through comparing the velocity spectra derived from different large CDP gathers,velocity scanning interval,time window length,cutting ratio of NMO,etc.,some effective advices on parameters selection for velocity analysis are given,and meanwhile,several noticeable problems in velocity analysis and time-depth conversion are discussed.

Key words: active fault, shallow seismic exploration, data processing, velocity analysis, parameter selection