海南琼华-莲塘断裂带第四纪活动特征

Quaternary activity characteristics of the Qionghua–Liantang fault belt in Hainan

位于琼北福山凹陷与海口隆起边界的琼华-莲塘断裂带,是调节北东向北部湾陆内裂谷不均匀伸展的结果,该断裂带穿过海口市长流新区与环岛高铁重大工程,对海南自贸区规划建设具有直接影响。文章采用构造地貌调查、地球物理探测与钻孔联合剖面等方法,揭露琼华–莲塘断裂带由五源河–道心村断裂、永庄水库断裂及海口砖瓦厂断裂共3条北西向平行展布的高角度活动断裂组成,呈隐伏或半隐伏状态,总体表现为正断层性质。断裂带宽约1.8 km,长度约17 km,第四纪以来断裂垂直位移为8.7~41.6 m,均属于较强活动断裂。3条断裂最新活动时代均为晚更新世,垂直位移速率<0.1 mm/a,其中以海口砖瓦厂断裂错动速率最大。结合琼华–莲塘断裂带的形成构造背景、最新活动时代,及其与第四纪火山活动的关系,文章提出了海南自贸区规划建设及工程避让活动断裂的建议。

The Qionghua –Liantang fault belt, located at the boundary between the Fushan depression and the Haikou uplift, is the result of the impact of the uneven extension of the NE-trending Beibu Gulf rift. The Qionghua–Liantang fault belt passes through the Changliu New District and the major projects of the island-looping high-speed railway in Haikou,directly impacting the planning and construction of the Hainan Free Trade Zone. The article uses tectonic geomorphic survey, geophysical exploration, and drilling exploration to reveal that the Qionghua–Liantang fault consists of three NWtrending buried and semi-buried normal faults, which are the Wuyuanhe–Daoxincun fault(F1-1), the Yongzhuangshuiku fault(F1-2), and the Haikouzhuanwachang fault(F1-3). The width of the Qionghua–Liantang fault belt is about 1.8 km,and the length is about 17 km. The vertical displacement of the fault belt is 8.7~41.6 m since the Quaternary. The latest active age of these three faults is the late Pleistocene;the vertical activity rate was less than 0.1 mm/a. It is worth noting that the vertical activity rate of the Haikouzhuanwachang fault(F1-3) is higher than the other two faults and has more vigorous activity. Combining the tectonic background, the latest active age of the Qionghua –Liantang fault, and its relationship with Quaternary volcanic activity, this paper puts forward suggestions on the planning and construction of the Hainan Free Trade Zone and building avoidance of active fault.