广西灵山断裂带构造应力场地质分析及活动性预测

摘要

Tectonic stress is one of the most active factors in the earth crust, therefore figuring out its mode of action and form of conversion is of great significance to guide the research on fault activity. Through a survey on many structural features in the Lingshan area, which include vertical folds, conjugated joints and scratch on faults surface, etc., we investigated the revolution characteristics of the tectonic stress field, mode of action and sequence of tectonic stress in the Lingshan area by structural analysis method. The results show that the region experienced four periods of function of tectonic stress field which came from four different directions: NW, NE, nearly EW and nearly SN. The force of NW appeared early than that of NE, and then the compression of nearly EW. We concluded that the structural framework of the study area has been formed by the effect of SN compressed stress which is still active today. Meanwhile, based on the geologic analysis of the mechanism of tectonic stress, we analyzed the structural stress quantitatively in the Lingshan area using finite element numerical simulation. The simulation demonstrated that the overlapping parts of strain intensive zone in higher value of maximum principal stress and lower value of maximum principal stress, such as, fault-bend parts, the fault intersections and the faults disappears site, have higher energy and prone to reactive in the later period. We think that the north of Mountain Luoyang, Fengtong, Tieling, Luwu are high stress concentration area, and the energy release is minor. And thus, we proposed a high-risk district and a sub-high-risk district in the Lingshan area is according to the size and scope of the stress.%构造应力是地壳中较为活跃的作用力之一，弄清构造应力作用方式和转变形式，对断裂活动性研究有重要的指导意义。以轴面近直立褶皱、共轭节理、断裂面擦痕等各种构造形迹为研究对象，采用构造解析分析方法，研究灵山地区构造应力场演化特征，确定灵山地区构造应力作用方式以及期次，认为整个研究区的构造格局在近 SN 向挤压应力的作用下而定型，该方向的挤压应力作用一直持续到现今。同时在构造应力场地质分析的指导下，运用有限元数值模拟手段，定量刻画了灵山地区现今构造应力场分布状态，确定最大主应力高值集中区与最大主应变量低值集中区的叠合部位：断裂弯曲、交汇与断裂尖灭相结合部位，具有能量集中程度较高特点，后期活动的可能性相对较大，并以此为依据圈定了灵山地区发生活动的高危区域和发生活动的次高危区域。