SEISMOLOGY AND GEOLOGY ›› 2019, Vol. 41 ›› Issue (3): 743-758.DOI: 10.3969/j.issn.0253-4967.2019.03.013

• Research Paper • Previous Articles     Next Articles

NEW EVIDENCE ON NE-SEGMENT OF JINTAN-RUGAO FAULT DISCOVERED BY SHALLOW SEISMIC EXPLORATION METHOD

GU Qin-ping1,2, YANG Hao1, ZHAO Qi-guang1, MENG Ke1, WANG Jin-yan1, LI Yun3, MA Dong-wei4   

  1. 1. Jiangsu Earthquake Agency, Nanjing 210014, China;
    2. Institute of Geophysics, China Earthquake Administration, Beijing 100081, China;
    3. Nanjing Institute of Geology and Mineral Resources, Nanjing 210016, China;
    4. Shenfeng Institute of Geological Techniques Co., Ltd, Shanghai 201107, China
  • Received:2018-04-11 Revised:2018-06-05 Online:2019-06-20 Published:2019-07-28

金坛-如皋断裂北东段浅层地震勘探新证据

顾勤平1,2, 杨浩1, 赵启光1, 孟科1, 王金艳1, 李云3, 马董伟4   

  1. 1. 江苏省地震局, 南京 210014;
    2. 中国地震局地球物理研究所, 北京 100081;
    3. 南京地质矿产研究所, 南京 210016;
    4. 上海申丰地质新技术应用研究所有限公司, 上海 201107
  • 作者简介:顾勤平,男,1983年生,高级工程师,2019年于中国地震局地球物理研究所获固体地球物理学专业博士学位,主要从事浅层地震勘探、活断层探测及天然地震层析成像研究工作,电话:025-84285628,E-mail:gqp1221@163.com。
  • 基金资助:
    中国地震重点监视防御区活动断层探测之栟茶河断裂活动性鉴定项目(1530601)、国家自然科学基金(41704052)和中国地震局地震科技星火计划项目(XY18017Y)共同资助。

Abstract: The NE-trending regional deep fault, i.e. the Jintan-Rugao Fault, is a boundary fault between the Subei depression and Nantong uplift, and its research has always received broad attention because of its importance and complexity. For the absence of definite proof, there is little consensus regarding the structure and spatial distribution of the fault among geoscientists, and its latest active time is ambiguous. The study of Quaternary activity characteristics of the Jintan-Rugao Fault is of great significance for earthquake trend prediction and engineering safety evaluation, and for earthquake prevention and disaster reduction in Jiangsu Province. In order to investigate the spatial location, characteristics and tectonic features and redefine the activity of the NE-segment of the Jintan-Rugao Fault, and on the basis of likely location and marker beds derived from petroleum seismic exploration sections, we collect and arrange 4 shallow seismic exploration profiles crossing the fault to conduct high-resolution seismic reflection imaging, following the working concept of ‘from known to unknown, from deep to shallow’. In this study, an observation system with trace intervals of 4~6m, shot intervals of 12~18m, and channels of 90~256 and 15~36 folds is used. In addition, by introducing different tonnage vibroseis to suppress the background noise, the raw data with high SNR(signal-noise ratio)can be obtained. By using the above working method and spread geometry, we obtained clear imaging results of the subsurface structure and fault structure in the coverage area of the survey lines. This exploration research accurately locates the NE-segment of Jintan-Rugao Fault, and further shows that it is not a single fault but a fault zone consisting of two normal faults with N-dipping and NE-striking within the effective detection depth. The shallow seismic profiles reveal that the up-breakpoint on the south branch with stronger activity is at depth of 235~243m, which offsets the lower strata of lower Pleistocene. Combining drilling data around the survey lines, we infer the activity time of this fault is early Pleistocene. The results of this paper provide reliable seismological data for determining the location and activity evaluation of the NE-segment of Jintan-Rugao Fault. In eastern China, where the sedimentary layer is thicker, the latest active age of faults can not be determined entirely according to the latest faulted strata. For a fault passing through the thicker area of new deposits, its latest active age should be based on the tectonic background, seismic activity, present tectonic stress field, topographic deformation, structural micro-geomorphological characteristics, sedimentary thickness of new strata, controlling effect of faults on new strata and the latest strata of faults, and combined with upper breakpoints, morphology, structure and occurrence of faults, the active state of the target concealed faults should be analyzed. If the activity of the fault is judged only by the upper faulted point, it may lead to overestimating the age of the fault activity.

Key words: Jintan-Rugao Fault, NE-segment, shallow seismic exploration, Quaternary activity

摘要: NE向的区域性深大断裂——金坛-如皋断裂为苏北坳陷区和南通隆起区的分界断裂。为了调查金坛-如皋断裂北东段的空间位置、性质和断裂构造特征并重新厘定其活动性,文中在石油地震勘探剖面提供的金坛-如皋断裂北东段大体空间位置及反射标志层的基础上,布设了4条浅层人工地震勘探剖面,对金坛-如皋断裂北东段进行了高分辨率地震反射成像,获得了测线控制范围内清晰的地下结构和断裂构造成像结果。结果表明,金坛-如皋断裂北东段并非单一的一条断层,而是由2条N倾、NEE走向的正断层组成的断裂带。浅层地震叠加剖面揭示活动性更强的南支上断点埋深235~243m,断错了下更新统底界,结合测线周边的钻孔资料推测其最新活动时代为第四纪早更新世(QP1)。文中的研究结果为确定金坛-如皋断裂北东段的位置及其活动性评价提供了可靠的地震学资料。

关键词: 金坛-如皋断裂, 北东段, 浅层地震勘探, 第四纪活动

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