Gravity inversion is a highly effective method for investigating regional geological structures, and this paper proposes an optimization scheme for constrained three-dimensional (3D) gravity inversion to obtain a 3D density model, utilizing prior geological and geophysics information. Specifically, the proposed method enhances deep structural imaging resolution and minimizes false structures by progressively inverting deep and shallow-density structures using long and short-wavelength signals of gravity anomaly with prior information. The scheme is applied in the southeast passive continental margin of Brazil, and the results show that the density model is consistent with the previous reflection and refraction seismic data. Moreover, the 3D density model reveals several insights: (i) The Abimael Ridge (AR) and the São Paulo Plateau (SPP) exhibit thin crustal thickness (∼5–7 km) indicative of proto-oceanic crust. The SPP and AR area crustal thinning may be related to an aborted opposing rift propagator pair. (ii) The rifting modes of Santos and Campos Basins differ significantly. Campos Basin exhibits a depth-dependent lithospheric stretching model with a relatively intact upper crust. In contrast, Santos Basin shows a highly brittle upper crust that is partially thinned and, in some regions, even absent under the far-field effect of spreading failed rifts, while the lower crust remains relatively intact. Moreover, the upper crustal stretching factor is about five to ten higher than the lower crustal. Thus, the constrained 3D gravity inversion scheme provides a new avenue for continental rifted margin geological structure studies.

中文翻译：

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复杂密度分布的约束 3D 重力反演：在巴西裂谷大陆边缘的应用

重力反演是研究区域地质结构的一种高效方法，本文提出了一种约束三维（3D）重力反演的优化方案，利用先验地质和地球物理信息获得3D密度模型。具体来说，所提出的方法通过使用具有先验信息的重力异常的长波长和短波长信号逐步反演深部和浅部密度结构，增强了深层结构成像分辨率并最大限度地减少了虚假结构。该方案在巴西东南被动大陆边缘应用，结果表明密度模型与前期反射、折射地震资料一致。此外，3D 密度模型揭示了一些见解：（i）阿比马埃尔海岭（AR）和圣保罗高原（SPP）表现出薄的地壳厚度（∼5-7 公里），表明原洋地壳。SPP 和 AR 区域地壳减薄可能与中止的相对裂谷传播器对有关。(ii)桑托斯盆地和坎波斯盆地的裂谷模式差异显着。坎波斯盆地表现出与深度相关的岩石圈拉伸模型，具有相对完整的上地壳。相比之下，桑托斯盆地显示出高度脆性的上地壳，该上地壳部分变薄，在一些地区甚至在扩展失败裂谷的远场效应下不存在，而下地壳则保持相对完整。而且，上地壳的拉伸系数比下地壳的拉伸系数大约高五到十倍。因此，约束三维重力反演方案为大陆裂谷边缘地质结构研究提供了新的途径。