【作者】 苏道磊；

【导师】 刘财； 刘希强；

【作者基本信息】 吉林大学 ， 地球探测与信息技术， 2010， 硕士

【摘要】 为了恰当地描述地球介质的非弹性特征,必须采用一个合适的物理参数对值特性进行描述。地球介质的品质因子(Q值)就可以很好地反映由于地球内部介质应力变化而引起的岩石性质的变化。地震波在介质中传播,其衰减强弱与介质(岩石)的性质密切相关,进而也能很好地反映介质品质因子的变化。一、研究目的在无法直接对地球介质进行研究的情况下,通过天然地震研究区域介质的Q值及频率衰减指数,了解某一区域地球内部介质的特性,把握区域应力总体特征。同时,给出不同频率的Q值随时间变化特征,为地震分析预报提供一定的科学依据。二、研究方法在总结众多介质品质因子计算方法的基础上,结合研究区域的地震活动特征,采用基于单次散射的S波及其尾波品质因子求解方法,对地震实例进行计算,得出研究结果。三、研究内容1、对利用尾波测量品质因子的方法进行了汇总,根据前人研究结果并结合具体实例讨论了品质因子与地震震源距、不同流逝时间的关系。2、为解决由于地震波在纵向介质中穿透深度的不同而导致不同地震之间的品质因子无法对比的问题,提出了在同一区域内,由散射波波阵面所围成的散射椭球体具有同一深度的技术思路,以此来确定尾波流逝时间。这样求取的品质因子能够有效去除地震波传播路径不同而造成的“假异常”现象。这种方法能较好地反映品质因子的异常变化与地震孕育过程的关系。3、以冀鲁豫交界地区为研究区域,选取符合条件的21次天然地震为研究对象,利用改进后的尾波测定方法,拟合得到了品质因子与频率之间的统计关系为Qc ? 28 .7f1.15,反映了该地区地震波平均衰减特性和应力总体特征,并与青岛崂山地区介质衰减特性进行了对比。4、初步分析了研究区域地震活动水平与不同频段尾波值的对应关系,得出区域构造应力随时间变化特征,以期捕捉到品质因子的时间变化与地震孕育过程的关系,进一步提高地震预测的准确率。通过地震实例分析,研究区域地震活动水平增强的过程与地震应力水平增强的过程较为一致。2009年下半年以来冀鲁豫交界地区地震活动增强,对应的高频段尾波Q值有所升高,表明研究区域构造应力随地震活动的增强而增强,应予以密切关注。更多还原

【Abstract】 Quality factor Q value is the description of the main parameters of earth medium properties. The changes of the properties of rock because of the changes of stress, such as the state of cranny, the transference of liquid, the upsurge of hot substance etc, will bring the changes of Quality factor. Because the attenuation of the seismic wave in the medium has a direct relation with the Quality factor, so to research the Quality factor of natural seismic and then to understand the properties of the medium inside the earth is one of the primary directions of research. Based on the predecessors’ research production, in order to reflect the change of the stress in the same area and remove the influence by the difference of ray paths of seismic wave, this paper improves the method to measure the Quality factor, and different earthquake using different passage of time measured methods. The physical model and measured method is scientific and innovative in some extent.According to previous research results, this paper studied seismic wave attenuation on the 21 earthquake records of Puyang station, and discussed the relationship between the quality factor with versus frequency; Using the determination method of coda wave quality factor , it eliminated effectively the impact on the quality factor measurements caused by the earthquake seismic wave scattering in the vertical penetration depth on the same or different earthquakes .It will help to capture relationship with the abnormal changes characteristics of the quality factor and the earthquake preparation process. Using the improved model, this paper calculated the Coda Wave Q value of Hebei-Shandong-Henan border, then given the relationship of Quality factor with frequency attenuation and the Temporal changes of the Regional media attenuation.更多还原