凤凰山地区蒲江-新津-德阳隐伏断裂反射波法地震勘探与断裂活动性研究

SEISMIC REFLECTION SURVEYING OF THE PUJIANG-XINJIN DEYANG BURIED FAULT IN FENGHUANGSHAN AREA AND THE STUDY OF FAULT ACTIVITY

利用反射波法地震勘探确定了在凤凰山地区蒲江-新津-德阳隐伏断裂通过的具体位置以及断裂的规模和性质,证明了该断裂在向东俯冲的过程中错切了晚更新统沉积物,具有明显的第四纪活动性,对凤凰山台地的形成起到了一定的控制作用。地面地质调查及历史地震研究也证明蒲江-新津-德阳隐伏断裂具有晚更新世活动性,且断裂南段的活动性明显强于北段,表明该断裂的北段是成都平原内部的一条弱地震活动带。同时,文中还对在城市近郊人烟繁杂地带反射波法地震勘探中野外观测系统的布置及地震参数的选取进行了探索,小道间距、小偏移距、多接收道、短排列、多次覆盖、高频检波器接收的工作方法和野外地震参数的合理选取对实现主要干扰波和反射波信号的有效分离,提高地震勘探分辨率起到了至关重要的作用。

The spatial distribution, scale and property of the Pujiang Xinjin Deyang buried fault in Fenghuangshan area were investigated by the use of seismic reflection survey technique. The result shows that the fault cut off the late pleistocene sediment in the process of eastward underthrusting, and has been significantly active since Quaternary. It has controlled to some extent the formation of the Fenghuangshan platform. Surface geological investigation and historical earthquake research have revealed that the Pujiang Xinjin Deyang buried fault were active during late Pleistocene. The activity of the south segment of the fault is obviously stronger than that of the north segment, indicating that the north segment of the fault is a zone of weak seismicity in the Chengdu Plain. At the same time, the layout of observational systems and the selection of seismic parameters for seismic reflection surveying of buried fault in densely populated suburban areas have been studied as well. It is found that the use of small group intervals, small offset, multiple channels, short array length, multiple coverage and high frequency receivers, as well as the appropriate selection of seismic parameters are of great significance to the effective separation of reflected wave from disturbing wave, and also to the improvement of the resolving power of seismic prospecting technique.