地震地质 ›› 2025, Vol. 47 ›› Issue (1): 267-283.DOI: 10.3969/j.issn.0253-4967.2025.01.016

• 研究论文 • 上一篇    下一篇

利用深地震反射剖面研究太行山南端的地壳精细结构和构造

酆少英(), 刘保金, 左莹, 姬计法, 谭雅丽, 丁奎, 武泉   

  1. 中国地震局地球物理勘探中心, 郑州 450002
  • 收稿日期:2024-07-10 修回日期:2024-09-23 出版日期:2025-02-20 发布日期:2025-04-09
  • 作者简介:

    酆少英, 男, 1967年生, 博士, 正高级工程师, 长期从事地壳深浅结构的反射地震探测与研究, E-mail:

  • 基金资助:
    地球深部探测与矿产资源勘查国家科技重大专项(2024ZD1000100); 中国地震局地质研究所国家野外科学观测研究站研究课题(NORSTY2022-05); 中国重点监视防御区活动断层地震危险性评价项目共同资助

THE STUDY OF FINE CRUSTAL STRUCTURE OF THE SOUTHERN MARGIN OF TAIHANG MOUNTAIN BY DEEP SEISMIC REFLECTION PROFILE

FENG Shao-ying(), LIU Bao-jin, ZUO Ying, JI Ji-fa, TAN Ya-li, DING Kui, WU Quan   

  1. Geophysical Exploration Center, China Earthquake Administration, Zhengzhou 450002, China
  • Received:2024-07-10 Revised:2024-09-23 Online:2025-02-20 Published:2025-04-09

摘要: 为研究太行山南端地壳精细结构, 在太行山南端的辉县—长垣之间布设了一条长约120km的深地震反射剖面。结果显示, 该区地壳结构分层特征性明显, 总地壳厚33.5~42.7km。上地壳厚13.3~20.1km, 东薄西厚; 下地壳有良好的反射性质, 由一系列反射能量较强的弧状或倾斜强反射构成。壳幔分界面反射能量较强, 横向连续性较好, 自东向西呈逐渐加深的形态。剖面沿线的断裂构造较为发育, 共解释了11条断层, 其中10条为上地壳内发育的断层。汤东断裂为汤阴断陷的主控边界断裂, 向下以铲形正断层方式切割了沉积地层和基底, 约在15~16km深度处归并到上、下地壳分界面上。在汤阴断陷的南东侧, 剖面上存在一个近垂直的条带状反射能量减弱带或壳内界面的不连续带, 自上而下切割了上、下地壳分界面、下地壳及壳幔分界面, 属于地壳尺度的深大断裂。该断裂带记录了与剖面下方软流圈上升流相关的岩浆底侵作用, 为深部热物质的上涌提供了通道, 而深部物质的上涌、岩浆底侵或热侵蚀作用导致地壳出现拉张伸展。

关键词: 深地震反射剖面, 太行山南端, 汤阴断陷, 华北盆地, 地壳深断裂

Abstract:

To investigate the fine crustal structure and tectonic characteristics of the southern margin of the Taihang Mountain, we conducted a deep seismic reflection survey along a 120km profile between Huixian and Changyuan.

Regarding data acquisition, we applied a geometry with a 25m group interval, 800 recording channels, and more than 60-fold coverage. The seismic wave explosion utilized a dynamite source of 30kg, with a hole depth of 25m. The shot interval was 200m. In data processing, the most critical aspect was improving the signal-to-noise ratio. The data processing workflow mainly included static correction(first-break tomography method), multi-type and multi-method denoising before stacking, amplitude compensation, surface-consistent predictive deconvolution, several iterations of velocity analysis and residual static correction, dip movement correction, and post-stack finite-difference migration.

A seismic section with a high signal-to-noise ratio was obtained, revealing the fine crustal structure along the survey line. The crustal structure in the section exhibits clear stratification, with crustal thickness ranging from approximately 33.5km to 42.7km. The crust contains distinct reflective structures from top to bottom, being thinner in the southeast and thicker in the northwest. The upper crust is about 13.3km thick in the southeast and approximately 20.1km in the northwest. The basement reflection deepens from west to east along the profile. In the southern Taihang Mountain, the depth of the basement reflection is about 1.0~1.5km in the northwest side of the Tangyin fault depression. Within the Tangyin fault depression, the basement reflection depth is approximately 3.5~4.0km. East of stake 56.0km, the basement surface tilts eastward, with its deepest point reaching approximately 8.0~10.0km. The lower crust exhibits strong reflective properties, consisting of a series of high-energy reflection waves, with inclined and arc-shaped strong reflections indicating significant heterogeneity in lower crust composition.

The Moho shows relatively strong reflected energy and good lateral continuity. It gradually deepens from southeast to northwest, with its shallowest depth at approximately 33.5km.

Numerous fault structures are observed along the deep seismic reflection profile. We identified ten faults in the upper crust and one deep fault. In the northwest section of the profile, three faults form a Y-shaped distribution. The upper part of the fault disrupts the bottom boundary of the Q+N strata and disappears downward into the upper crust. The Tangdong fault is the main controlling boundary fault of the Tangyin fault depression. It cuts through the shallow sedimentary strata and basement reflection wave groups as a shovel-shaped normal fault and disappears into the upper crust. The Tangxi fault and Tangzhong fault merge into the Tangdong fault at depths of approximately 8.0~10.0km and 5.0~6.0km, respectively. The Changcun fault and Changyuan fault, located in the eastern section of the profile, appear in the strata beneath the Neogene and terminate at the interface between the upper and lower crust, without cutting through the upper Q+N strata. The Yellow River Fault is a large-scale fault in the Dongpu depression and serves as the eastern boundary fault of the depression. Its shallow section consists of two inclined faults, with the main fault being a northwest-trending normal fault.

The deep fault appears as a nearly vertical weak-reflection energy strip on the section or as a discontinuous zone of reflection characteristics, located on the southeast side of the Tangyin fault depression. This fault zone represents a major deep crustal fault. It offsets intracrustal interface reflections, lower crustal reflection bands, and the crust-mantle interface reflection. The deep fault in the crust has become a channel, facilitating the upwelling of deep hot material. The upwelling of deep material, magma underplating, or thermal erosion leads to the tensile extension of the crust and lithospheric thinning, potentially altering crustal structure and material composition.

Key words: deep seismic reflection profiling, the southern margin of Taihang Mountain, Tangyin graben, north China Basin, deep crustal fault