关键词: 汤东断裂, 浅层地震, 三维建模, 几何结构特征, 反射地震剖面

Abstract:

Accurate characterization of shallow fine-scale geometric structures in active faults is critically important for earthquake disaster prevention, mitigation efforts, and advancing our understanding of seismic mechanisms. Integrated approaches combining artificial seismic exploration with three-dimensional structural modeling provide powerful capabilities for revealing detailed spatial architectural characteristics of buried fault systems. This study investigates the Tangdong buried active fault along the seismically significant southeastern margin of the Taihang Mountains, employing advanced geophysical methods to elucidate its complex geometric configuration and kinematic behavior.
High-resolution imaging was achieved through a targeted small-spacing shallow reflection seismic exploration survey. A comprehensive array of 10 survey lines spanning a cumulative length of 28km yielded high-quality seismic reflection datasets. Advanced data processing techniques, including noise attenuation and velocity analysis, were applied to generate optimal high-resolution seismic profiles. These profiles enabled detailed structural interpretation of fault geometry and displacement characteristics. Subsequently, a geometrically constrained 3D fault model was constructed using the SKUA-GOCAD software platform, facilitating comprehensive spatial analysis of the fault system.
Key findings reveal the Tangdong Fault as a high-angle normal fault with a dominant North-Northeast(NNE)strike direction. Significant along-strike segmentation characterizes its shallow architecture: the northern segment features a bifurcated structure comprising two distinct subsidiary faults(F_3-1 and F_3-2). In contrast, south of Weixian Town, these faults converge into a single strand(F_3-2). Shallow dip angles exhibit considerable spatial variation, ranging from approximately 55° to 80°. Notably, the central segment between survey line L6(Panshitou Xincun) and line L7(north of Gangpo Village)displays a relatively gentler dip angle compared to adjacent segments, resulting in a distinctive saddle-shaped geometric configuration.
Clear spatial partitioning of recent activity is observed between the subsidiary faults. South of survey line L6, contemporary deformation is predominantly localized on Fault F_3-2, whereas north of L6, activity is exclusively manifested on F_3-1. Integration of deeper-penetration petroleum seismic profiles confirms the fault's listric geometry, characterized by a steep upper section that progressively shallows with depth. The eastern(F_3-1) and western(F_3-2)branches converge and merge into a unified fault plane at approximately 1.8km depth. The 3D structural model further validates this geometric configuration near line L4 in Weixian Town and effectively visualizes the along-strike dip variations.
These comprehensive findings provide fundamental insights into the three-dimensional geometry, segmentation patterns, and kinematic behavior of the Tangdong active fault. The integrated methodology significantly enhances our understanding of neotectonic deformation processes, offering critical scientific support for fault avoidance zoning, seismic hazard assessment, and earthquake risk mitigation strategies in this tectonically active region. This robust methodological framework establishes a transferable approach for characterizing concealed active fault systems in analogous tectonic settings globally.

Key words: Tangdong Fault, showllow seismic, three-dimensional modeling, geometric structure feature, reflection seismic profile