地震地质 ›› 2022, Vol. 44 ›› Issue (2): 333-348.DOI: 10.3969/j.issn.0253-4967.2022.02.004

• 研究论文 • 上一篇    下一篇

小多道地震震源效果在海域活动断裂探测中的对比研究

易虎1,3)(), 詹文欢1,2,3), 闵伟4), 吴晓川1), 李健1), 冯英辞1,2), 任治坤4),*()   

  1. 1)中国科学院边缘海与大洋地质重点实验室, 南海海洋研究所, 南海生态环境工程创新研究院, 广州 511458
    2)南方海洋科学与工程广东省实验室(广州), 广州 511458
    3)中国科学院大学, 北京 100049
    4)中国地震局地质研究所, 北京 100029
  • 收稿日期:2021-05-06 修回日期:2021-07-02 出版日期:2022-04-20 发布日期:2022-06-14
  • 通讯作者: 任治坤
  • 作者简介:易虎, 男, 1990年生, 现为中国科学院南海海洋研究所海洋地质专业在读博士研究生, 主要从事海洋新构造与地质灾害研究, E-mail: yihu20@mails.ucas.ac.cn
  • 基金资助:
    国家重点研发计划项目(2017YFC1500401);国家科技基础资源调查专项(2017FY201406);南方海洋科学与工程广东省实验室(广州)人才团队引进重大专项(GML2019ZD0204)

A COMPARATIVE STUDY OF SOURCE EFFECT BASED ON MINI-MULTICHANNEL SEISMIC PROFILE IN MARINE ACTIVE FAULT DETECTION

YI Hu1,3)(), ZHAN Wen-huan1,2,3), MIN Wei4), WU Xiao-chuan1), LI Jian1), FENG Ying-ci1,2), REN Zhi-kun4),*()   

  1. 1) Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Innovation Academy of South China Sea Ecology and Environmental Engineering, Chinese Academy of Sciences, Guangzhou 511458, China
    2) Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou), Guangzhou 511458, China
    3) University of Chinese Academy of Sciences, Beijing 100049, China
    4) Institute of Geology, China Earthquake Administration, Beijing 100029, China
  • Received:2021-05-06 Revised:2021-07-02 Online:2022-04-20 Published:2022-06-14
  • Contact: REN Zhi-kun

摘要:

海域地震区划与活动断裂的探测和识别密切相关。文中在台湾海峡闽东南隆起带开展了活动断裂的地球物理探测研究, 选取GI枪震源与电火花震源剖面进行对比分析, 发现了晚更新世以来活动的3条基底断裂构造和2条垂向延伸较小的细小断裂。基底断裂可在GI枪震源剖面和电火花震源剖面上识别, 细小断裂则只能在电火花剖面上识别; 3条基底断裂在2种剖面上的错断地层位置、 几何形态接近, 但断裂周围的地层形态及次级断裂展布样式受分辨率的影响存在成像差异。相似的断裂探测结果体现了这2种方法的有效性, 而剖面成像差异则说明在实际工作中开展组合探测的必要性。基于2种数据的融合结果, 对断裂F1的构造属性进行更为详细的分析说明: 断裂F1是基底先存断裂晚更新世活化的结果, 为一坳陷边界断层, 呈伸展正断活动, 分析认为其应归属为华南沿海滨海断裂带。因此, 在海域地震区划和海域地震危险性评价工作中, 应重视多种探测方法的组合使用, 以便获取更加详实的断裂信息。

关键词: 电火花震源, GI枪震源, 小多道地震, 活动断裂, 台湾海峡

Abstract:

The neotectonic activity is intense in the Taiwan Straits and the coastal area of South China. This region is one of the earthquake-prone areas of the world. In history, earthquakes of magnitude 6-7 occurred repeatedly in this region with a high recurrence rate. Therefore, this area has always been the focus of seismicity research and coastal earthquake prevention and disaster reduction. The exploration of active faults is the basis for seismic zoning, but the detection and identification of active faults in sea area are more difficult because of the coverage of sea water, which leads to a large number of “blind areas” in marine fault exploration for a long time. Seismic exploration methods are economical, suitable and efficient in detecting active faults in the sea area. This study compares the detection effect of different seismic sources.
In this study, geophysical exploration of active faults was carried out in the southeast Fujian uplift zone in the Taiwan Straits. A mini-multichannel seismic profile of GI gun source and sparker source at the same location was selected for comparative analysis and illustration. Five reflection interfaces(T1—T4, Tg)were interpreted on the GI gun profile, and five sets of seismic sequences(A—E)were classified. Six reflection interfaces(T'1, T1—T4, Tg)were interpreted on the sparker source profile, and six sets of seismic sequences(A—D and E1—E2)were classified. Three basement faults and two shallow faults with small vertical extension were found, which are active since the late Pleistocene. Among them, the scale of fault F1 is large, the displacement of the basement fault F1 is 51ms, and the overall displacement of (T1—T4) in the sediments is 35ms. Faults F2—F5 are located on the continental side of fault F1 and can be combined into grabens and horsts in forms, which are inferred to be the associated faults of Fault F1. It’s found that basement faults can be identified by both GI gun profile and sparker source profile, while the small faults can only be identified by the sparker profile. At the same time, the depth of upper breakpoint on the sparker profile is shallower, and the latest fault activity can be traced back to the Holocene. The locations and geometrical shapes of the three basement faults are similar on the two profiles, but there are imaging differences in the formation shapes around the faults and the distribution patterns of the secondary faults due to the influence of resolution. The similarity of fault detection results shows the effectiveness of the two methods, while the difference of profile imaging shows the necessity of combined detection in practical work.
According to the comparison of the two kinds of data, the sparker profile reveals a finer shallow structure than the GI gun profile does, and the GI gun profile can obtain a clearer basement structure. Based on the fusion results of the two kinds of data, the structural attributes of fault F1 are further analyzed and explained in detail in this paper, and the Fault F1 is the result of the reactivation of a basement pre-existing fault in the late Pleistocene and is a depression-boundary fault with an activity pattern of extensional normal faulting, and it is considered in this paper to be part of the South China Binhai fault zone. Therefore, it is necessary to attach importance to the combination of multiple detection methods in marine seismic zoning and marine seismic hazard assessment in order to obtain more detailed fault information.

Key words: sparker source, GI gun source, mini-multichannel seismic, active fault, Taiwan Straits

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