海南岛北部马袅—铺前断裂东段活动性与地壳稳定性评价

Activity of eastern part of the Maniao-Puqian fault in northern Hainan Island and its evaluation of crustal stability

近东西向展布的马袅—铺前断裂是琼北地区主要活动断裂之一,也是1605年琼山7.5级地震主要控震断裂之一,其活动性对评价海南岛北部地壳稳定性及地质灾害预测有着重要意义。本文通过遥感解译、活动断裂断错地貌填图、高密度电法剖面测量、联孔剖面钻探验证等方法,查明了马袅—铺前断裂东段的空间展布特征:8条北东东向展布、北倾或南倾的正断层F_(2-1)~F_(2-8)组成三堑夹两垒构造,继承上新世之前的多期活动断裂。年代学测试结果鉴别出5条全新世活动断裂(F_(2-1)、F_(2-4)、F_(2-6)、F_(2-7)、F_(2-8)),2条前第四纪断裂(F_(2-2)、F_(2-5))和1条早中更新世断裂(F_(2-3));全新世以来F_(2-1)、F_(2-7)、F_(2-8)断裂垂直活动速率为0.43~1.79 mm/a;F2-4、F2-6断裂垂直活动速率为0.12~0.33 mm/a。结果表明,东寨港东岸地区处于不稳定区,应加强断裂活动的监测力度,工程建设时应按照相关标准进行规避。

The Maniao-Puqian fault trending east-west,as the major one controlling the Qiongshan earthquake registered 7.5 magnitude on Richter scale in 1605,is a major active fault in the northern Hainan area.Hence,its activity's measuring is critical for crustal stability evaluation and for geological hazard forecast in the northern part of Hainan Island.Various methods were used to determine the distribution of the eastern part of this fault,including remote sensing images interpretation,fault landform mapping,high-density electrical detecting and cross-section drilling validation.The results show that it is spatially composed of 8 northdipping or south-dipping NEE-trending normal faults(F2-1~F2-8),constituting the three-graben and two-barrier structure,and inheriting the multi-stage activities from the faults before the Pliocene.Five Holocene active faults(F2-1,F2-4,F2-6,F2-7 and F2-8),two pre-Quaternary faults(F2-2 and F2-5)and one early Miocene fault(F2-3)were identified by chronological tests.Moreover,the vertical movement rate of F2-1,F2-7 and F2-8 was 0.43-1.79 mm/a,while that of F2-4 and F2-6 between 0.12-0.33 mm/a since Holocene.The above research shows that the structures in this area are all in an active state,which has a great influence on the future engineering construction,and the monitoring efforts must be strengthened.