北京八宝山断裂带近期构造活动及其和地震的关系

RECENT TECTONIC MOVEMENT OF THE BABAOSHAN FAULT NEAR BEIJING AND ITS RELATION TO EARTHQUAKE OCCURRENCES

  • 摘要: 本文根据地质、形变测量、地下水和小震活动等资料, 对八宝山断裂带的近期构造活动特征进行了研究, 指出从1972年到1976年唐山地震前, 八宝山断裂活动方式在不同阶段表现不同.1973年9月以前为张性右旋运动, 从1973年9月到唐山地震前为压性左旋运动.其中有短期加速活动时期.断裂加速活动过程中, 在八宝山断裂西盘, 三口基岩深井地下水位的升降有明显的从南向北变化特征.1973年6月, 南部歇息岗井水位开始上升, 7月大灰厂井水位上升, 10月北部板桥井水位上升;另一次水位下降变化是1975年4月至7月, 是年4月南部歇息岗井水位开始下降, 5月大灰厂井水位下降, 7月北部板桥井水位下降.大灰厂的地形变和水位同时发生变化.上述现象可能解释为八宝山断裂蠕动是从西南向东北逐渐传递形成的.近十几年来, 八宝山断裂带附近的小震活动集中在该断裂的西北侧和在北西向南口——孙河断裂西南侧, 这可能是由于八宝山断裂蠕动在向东北方向传递过程中, 受到北西向的南口——孙河断裂阻挡所致.

     

    Abstract: Basing on the geological framework, ground level deformation, underground water level changes and seismicity data, the character of the recent tectonic movement of the Ba Bao Shan Fault has been investigated. It is shown that during the time period from 1972 to the Tang Shan earthquake of July 1976, the type of tectonic movement of this fault was different for different intervals of time. Before September 1973, it was ten-sional and right lateral; after that time, the movement became compressional and left lateral and till the outbreak of the Tang Shan earthquake, there was accelerated movement along that fault for a short duration accompanied by variations of underground water level, starting from the southern portion towards the north in three deep wells drilled into bed rock on the western side of the fault.In June 1973, water level began to rise first in the Xie Xi Gang well to the south, and then in July and in October, the water level in the Da Hui Chang well and the Ban Qiao well to the north rose respectively. On the contrary, from April to July of 1975, obvious lowering of water level was observed in the wells. First, water level in the Xie Xi Gang well began to descend in April and then that of the Da Hui Chang well and Ban Qiao well also lowered in May and in July respectively.It was noted that while the water level of the Da Hui Chang well was lowering, there was also ground level deformation around that well.All such phenomena may be explained as the effect of the creep of the Ba Bao Shan Fault which was transmitting from the southwest to the northeast gradually. For the last more than ten years, small earthquake in the vicinity of the fault concentrated in a zone to the northwest of this fault and to the southwest of the northwest-trending Nan Kou-Sun He fault. It might be explained as the result of the barrier effect of the latter to the northeasterly creep movement of the Ba Bao Shan Fault.

     

/

返回文章
返回