深圳北西向断裂分布特征及其活动性研究

A STUDY ON DISTRIBUTION CHARACTERISTICS AND ACTIVITY OF NORTH-WEST FAULTS IN SHENZHEN

深圳地区断裂以北东向五华—深圳断裂带和北西向珠江口断裂带多条次级断裂相互切错的断裂空间分布特征为主,同时多组东西向断裂穿插其间组成复杂的"棋盘格子状"断裂系统。北东向和北西向断裂是现今活动的发震构造,自有地震记录以来在深圳市及其周边发生的多起微震事件表明北西向和北东向断裂活动仍在持续,尤其是近百年来珠江口断裂带发生的多起中强震更是佐证了这一观点。针对深圳南山区及周边北西向断裂的第四纪活动性研究,从露头区实地断层追索、断层特征的考察以及已有钻孔和地球物理资料收集等方法入手分析总结了深圳地区北西向主要断裂的分布特征和活动性:深圳地区北西向断裂在空间上控制了珠江口断陷,区域上切割北东向断裂,空间分布连续性较差;北西向断裂最新活动于晚、中更新世,部分断裂表现为老断裂新活动,最新活动时间存在明显分段特征。全新世以来活动性明显减弱,部分次级断裂属于弱活动或不活动断裂。

The faults in Shenzhen constitute a complex grid-shaped fault system, mainly dominated by multiple secondary faults interlacing with each other in the NE-trending Wuhua-Shenzhen fault zone （WSFZ） and the NW-trending Pearl River Mouth fault zone （PRMFZ） and several WE-trending faults cutting through. WSFZ and PRMFZ are both seimogenic structures now. Series of seismogenic events occurred in Shenzhen and Pearl River Mouth indicate that structural movements are still active in the joint of NE and NW faults, which has been prove by several intense quake events during the past hundreds of years. This paper is focused on the NW-trending faults’ activity in Quaternary. The distribution characteristics and activity of the NW-trending faults in Shenzhen are analyzed and summarized by means of field fault tracing, investigation of fault features, existing borehole and geophysical data collection. The results show that NW-trending faults spatially controls the Pearl River Mouth sag and regionally cuts through NE-trending faults, with poor spatial distribution continuity. The NW-trending faults were lately activated during the upper and middle Pleistocene, most of which were old faults with new movements, and recent movements happened with obvious intervals. Movements apparently weakened during the Holocene, and most secondary faults were hardly active or inactive.