Downward continuation can enhance small‐scale sources and improve resolution. Nevertheless, the common methods have disadvantages in obtaining optimal results because of divergence and instability. We derive the mean‐value theorem for potential fields, which could be the theoretical basis of some data processing and interpretation. Based on numerical solutions of the mean‐value theorem, we present the convergent and stable downward continuation methods by using the first‐order vertical derivatives and their upward continuation. By applying one of our methods to both the synthetic and real cases, we show that our method is stable, convergent and accurate. Meanwhile, compared with the fast Fourier transform Taylor series method and the integrated second vertical derivative Taylor series method, our process has very little boundary effect and is still stable in noise. We find that the characters of the fading anomalies emerge properly in our downward continuation with respect to the original fields at the lower heights.

The tectonic boundaries and geodynamic evolution of the South China Block are widely debated. While the community largely agrees on the occurrence of the collision between the Yangtze and Cathaysia Blocks, the lack of ultrahigh-pressure metamorphic rocks and obscurity of the boundary lead to inconsistencies among the abundant geological and geophysical data. We present three profiles that reveal the geoelectrical structure of eastern South China. Distinct conductive interfaces oriented NE–SW are identified in the geoelectrical lithosphere, which separate the region into six parts. To interpret our observations and resultant model, we develop and propose a mechanism of “microcontinent interaction”. Our new model justifies the prior proposed models of ‘block collision’ and additionally proposes ‘multi-terrane accretion-collision’ to address the tectonic evolution.

Massive lithospheric thinning occurred in eastern China and large‐scale magmatism in South China occurred in the Mesozoic. Some geodynamic models have been proposed to explain their mechanisms, but are not consistent with each other. We apply anisotropic tomography to 32,728 P‐wave travel time data of 479 teleseismic events recorded at 225 stations to study the 3‐D anisotropic Vp structure of the upper mantle beneath central‐east China. P‐wave radial anisotropy is investigated for the first time in the study region. Our results show that an obvious low‐velocity zone exists in the asthenosphere under the eastern part of our study region, which represents upwelling thermal flow from the Cathaysia block to the North China block (NCB) according to the results of azimuthal and radial anisotropies. A distinct high‐velocity zone with weak radial anisotropy exists under the middle Yangtze block, which is explained as the stable cratonic root. Two other weak high‐velocity zones appear near or within the mantle transition zone under the middle‐lower Yangtze River and the eastern NCB, which might be detached lithosphere or the stagnant Pacific slab. Combining with previous geological and geochemical results, we consider that both the NCB and the South China block have undergone a common geodynamic process in the Mesozoic due to their similar age trending of igneous rocks, which could be explained by a flat‐slab subduction model and a ridge subduction model. These two models are associated with the paleo‐Pacific plate subduction that might have played a key role in the evolution of eastern China.