【摘要】 活断层探测是断层活动性评判的基础,也是天然地震灾害预防的依据,而浅层地震勘探是活断层探测的有效方法之一;而目前利用浅层地震方法评判断层活动性的能力亟待提高.通过构建了不同宽度破碎带的活断层理论模型,采用二维粘弹性波动方程有限差分法进行了波场响应特征模拟,运用希尔伯特变换方法提取了瞬时频率和相位属性.结果表明:地震水平叠加剖面和瞬时属性相结合可有效获取穿过第四系活断层的响应特征和实现断层活动性评判;当相干噪声达到30%时,水平叠加和瞬时频率属性剖面已难以追踪第四系中弱反射信号,而瞬时相位属性剖面仍可有效追踪;在实际活断层判定中,水平叠加、瞬时频率与瞬时相位地震属性剖面均可判断断层的存在,而穿过第四系的断层(或破碎带)特征瞬时相位属性最为明显和突出,水平叠加剖面次之,瞬时相位地震属性是判定断层活动性的重要和有效的属性.更多还原

【Abstract】 Active fault detection is not only the foundation for the fault activity evaluation,but also the basis for prevention of natural earthquake disasters.The shallow seismic exploration is one of the effective methods for active fault detection.This study aims to further improve the fault activity evaluation with shallow seismic methods.We construct theoretical models of active fault of different fracture zone widths,apply the finite difference method of two-dimensional viscoelastic wave equation to simulate wave field response characteristics,use Hilbert transform method to extract the attributes of instantaneous frequency and instantaneous phase,and analyze the performance in the field of anti-noise and effect of practical applications of method.The results show:Combination of the vertical travel time section and seismic attributes can effectively obtain the response characteristics of active faults which cut through the Quaternary and achieve the evaluation of fault activity;However,when coherent noise reaches thirty percent,it is difficult to trace and identify the weak reflection signals in the Quaternary by the vertical travel time section and instantaneous frequency section,but instantaneous phase attributes can still effectively trace and identify the weak reflection signals with a high anti-noise ability.In the practical determination of active faults,both the vertical travel time section,instantaneous frequency section and instantaneous phase section can determine the existence of faults.The instantaneous phase attribute is the most obvious and prominent to show the characteristics of faults or fracture zones which cutthrough the Quaternary,whereas the vertical travel time section takes the second place.It is concluded that the instantaneous phase attribute is an important and effective seismic attribute to determine the fault activity.更多还原