西江断裂三水至磨刀门段第四纪活动性再研究

Re-visiting the Quaternary activity of Xijiang Fault from Sanshui to Modaomen

西江断裂是珠江三角洲北西向主干断裂。为进一步查清其第四纪活动性,进行了1︰5万地质地貌填图、浅层地震探测、断层活动年代测定、联合钻孔验证、构造解析等工作。结果表明,第四纪地貌与断裂特征具有一定耦合性,历史地震等说明西江断裂目前仍有一定活动性;地质调查及浅层地震、联合钻孔验证均未发现断裂切割第四系;年代测量结果表明断裂在中更新世至晚更新世前期活动性较强,晚更新世晚期以后活动性渐弱;前人对磨刀门大桥的构造解析表明,断裂两侧存在沉降速率突变现象,但相对变化属弱形变。综合研究认为,西江断裂目前仍有一定活动性,但活动性较弱。

The Xijiang Fault is an important fault of the Pearl River Delta. To learn the quaternary activity of the Xijiang Fault furtherly, geological mapping in 1︰50000 scale, age dating, shallow seismic reflection and drilling verification were performed. The results show that the quaternary geomorphology and fracture coupled. The character of historical seismic reflection shows the fault is still active. Field survey and shallow seismic reflection show that the fault didn’t cut quaternary strata. Chronology shows that the activity strength was relatively strong before the Late Pleistocene, and became weak afterward. Tectonic analysis of Modaomen indicates that there is a sudden change in the sedimentation rate at both sides of the fault, but activity strength is weaker. In short, the Xijiang Fault is still active, but its strength is weak.