关键词: 断裂特征, 变形机制, 盆地演化, 莺东断裂体系, 莺歌海盆地

Abstract: The eastern fault system of Yinggehai Basin (Yingdong fault system) exhibits a complex structural architecture, and its deformation characteristics and genetic evolution require further in-depth investigation. Based on newly acquired two-dimensional wide-line and three-dimensional high-resolution seismic data, this study systematically delineates the structural deformation features of the fault system. Integrating insights from regional plate interactions and deep crust-mantle structure, the tectonic evolution of the basin and its controls on differential deformation of Yingdong fault system are further examined. The results indicate as follows. (1) Three principal fault sets trending NW-SE (NWW-SEE), NE-SW, and near North-South direction are developed in the east of basin, controlling the formation of multiple half-grabens, fault steps, and intra-sag uplifts. Among them, Fault No.1 functions as a first-order basin-bounding fault, together with NW-SE (NWW-SEE) trending second- and third-order faults within Yinggehai sag, constitutes a broom-shaped extensional strike-slip fault system. (2) Yingdong fault system was mainly active during the Oligocene (sedimentary period from Lingtou Formation to Lingshui Formation), controlling the initial rifting and subsequent extensional strike-slip rifting of the basin. However, since the Miocene (sedimentary period of the Sanya Formation), the basin has evolved into a subsiding depression with progressive fault activity attenuation. (3) The basin exhibits a tectonic deformation pattern characterized by "compression in the north and extension in the south". Correspondingly, the activity intensity of Yingdong fault system shows a pattern of "stronger in the south and weaker in the north", with significant differences in tectonic deformation between the southern and northern segments of the basin. (4) The tectonic evolution of Yinggehai Basin and its eastern fault system is jointly governed by the coupling of the deep mantle upwelling to thermal subsidence cycles and the rotational extrusion associated with the Indochina Block. The mantle upwelling to thermal subsidence process dominates the "early faulting and late-stage depression" structural framework, whereas the extrusion and lateral escape of the Indochina Block induce regional strike-slip tectonics, leading to the development of the eastern broom-shaped fault system and the marked differential deformation between the northern and southern segments of the basin.

Key words: fault characteristics, deformation mechanisms, basin evolution, Yingdong fault system, Yinggehai Basin