西淋岗第四系断层探测及活动性评价

Detection and Activity Estimation of Quaternary Fault in Xilingang Area

利用地质雷达、氡气测量和释光测年方法对珠江三角洲北部西淋岗断裂进行探测并界定了地层年龄。结果表明:在晚更新世期间,西淋岗地区发生了至少2次突发性断裂活动。第一次活动在距今4万a左右,断层上盘地块发生了较大幅度的单边倾倒,造成断层两盘产生了近5.5 m的断距,形成了第四系内的角度不整合接触;在距今2万a之后,断裂第二次活动,形成了地表所见到的0.53 m地层错动。此外,断裂上方土壤氡气异常峰值大于背景值3倍,这说明了西淋岗断裂具有活动性和潜在危险性,也改变了珠三角地区断裂为'蠕滑断裂'的认识。

Ground penetration radar,luminescence dating and radon measurement were used to detect the Xilingang fault in Pearl River Delta.The results illustrate that during the Late Pleistocene epoch,at least two paroxysmal fault movements happened in the research area.The first movement happened about 40 000a ago,causing a block inclination of hanging wall,and an unconformity interface among the Quaternary strata;the slip of the fault reached to 5.5 m.The second paroxysmal movement,which happened 20 000a ago,causing the fault slip about 0.53 m.The peak value of radon on the fault is three times higher than the background value.All the evidences demonstrate that the Xilingang fault is active and has potential dange,therefore the conclusion that the faults located in the north of Pearl River Delta were non-active and steady should be changed.