The deep learning-based gravity anomaly inversion method addresses the complex challenge of deriving subsurface density variation models from surface gravity anomaly data. In order to generate various geological environments and their corresponding surface gravity anomaly datasets, three-dimensional density models considering different spatial locations and density variations are created in this paper. At the same time, the residual module and spatial attention mechanism are introduced into the U-Net architecture to improve the learning ability and inversion accuracy of complex geological structures. Experimental results demonstrate that the proposed method achieves the high-precision reconstruction of density variation models in complex anomaly environments, with a model residual error lower than 3%. Additionally, the inversion results of the density change and the gravity change in the Longshoushan fault zone show that the 2022 Menyuan MS6.9 earthquake is in the middle of the positive and negative density changes, which verifies the applicability of the U-Net network in the field of gravity change data, highlighting the method’s value in the real-world environment.

The Sichuan-Yunnan block, characterized by complex geological formations and persistent high-intensity seismicity, remains a focal domain for contemporary geodynamic research. To investigate the fracture depth of the northern Sichuan-Yunnan block and the southeastern part of the Qiangtang block, CRUST1.0 was employed to fit the trend items in the study area and to refine the gravity field model with measured data as control points. A two dimensional discrete wavelet transform analysis method is applied to separate the field sources from the obtained high-precision grid data. Additionally, radial logarithmic power spectrum analysis is utilized to estimate the average equivalent source depth of the abnormal geological bodies corresponding to each order wavelet, thereby extracting both transverse and longitudinal tectonic characteristics of the crust in the region. The results reveal that the Bouguer gravity anomaly within the study area exhibits a general pattern of low values in the northern region and high values in the southern areas. Major faults, including the Bianba-Luolong fault, Nujiang fault, Lancangjiang fault, Batang fault, Jinshajiang fault, Yushu-Ganzi fault and Ganzi-Litang fault are all deep and large faults, with respective depths of 38.9 km, 52.9 km, 52.9 km, 52.9 km, 38.9 km, 52.9 km, 52.9 km. This study provides physical insights into the crustal structure distribution of the northern Sichuan-Yunnan rhombohedral block.

Geophysical forward modeling serves as a fundamental theoretical approach for characterizing subsurface structures and material properties, essentially involving the computation of gravity responses at surface or spatial observation points based on a predefined density distribution. With the rapid development of data-driven techniques such as deep learning in geophysical inversion, forward algorithms are facing increasing demands in terms of computational scale, observable types, and efficiency. To address these challenges, this study develops an efficient forward modeling method based on voxel discretization, the enabling rapid calculation of gravity anomalies and radial gravity gradients on multiple observational surfaces. Leveraging the parallel computing capabilities of graphics processing units (GPU), together with tensor acceleration, Compute Unified Device Architecture (CUDA) execution, and Just-in-time (JIT) compilation strategies, the method achieves high efficiency and automation in the forward computation process. Numerical experiments conducted on several typical theoretical models demonstrate the convergence and stability of the calculated results, indicating that the proposed method significantly reduces computation time while maintaining accuracy, thus being well-suited for large-scale 3D modeling and fast batch simulation tasks. This research can efficiently generate forward datasets with multi-view and multi-metric characteristics, providing solid data support and a scalable computational platform for deep-learning-based geophysical inversion studies.