Based on the teleseismic records of the dense broadband seismic array, the crustal anisotropy parameters of the west Ordos block and its adjacent regions were determined with P wave receiver functions. The results indicate that the dominant direction of the fast wave is NEE‐SWW, N‐S in Yingshan block and north Ordos block, N‐S in the south Ordos block, and E‐W in the Qinling–Dabie orogen belt. The fast wave direction of crustal anisotropy in the north Ordos block is distinctly different from that in the south Ordos block, both well related to the major geological events, such as the Paleoproterozoic continent‐to‐continent collision between the Ordos Block and the Yinshan Block, the collision between the Western Block and Eastern Block of the North China Craton and the material migration from the Tibetan plateau in Cenozoic. Our results indicate that the crustal anisotropy in the Ordos block preserves the traces of ancient tectonic movements. Combining the results of previous geophysical studies, we presented a crust‐mantle interaction model to explain the geophysical observations. The most prominent features of the model are the horizontal eastward expansion of the mantle material in the southern Ordos and the vertical upwelling of the mantle material in the northern Ordos. The different modes of movement of the mantle material led to the deep contrasting structures of north and south Ordos, including the crustal anisotropy. The mantle upwelling also implies that the north Ordos block might be currently experiencing craton destruction.

To evaluate the prospects of multi-antenna GNSS buoy and mooring array in ocean altimetry satellite calibration, experiments are conducted in the ocean around Qianliyan islet in China’s Yellow Sea. The trials aim to validate the feasibility of establishing an ocean altimetry satellite calibration site while assessing the performance of relevant calibration equipment. Utilizing one multi-antenna GNSS buoy system and one mooring array operating for over 20 days, the experiment incorporates continuous GNSS observation data from Qianliyan islet’s permanent station. Results reveal that high-frequency sea surface height (SSH) signals exhibit periods approaching or below 10 s, with the designed low-pass filter effectively attenuating these high-frequency components. Significant differences emerge in the power spectra of filtered SSH measurements between instruments: high-frequency signals detected by the mooring array demonstrate greater spectral concentration and lower signal intensity than those recorded by the GNSS buoy. Through multi-day synchronized observations, the height datum for mooring array SSH measurements is obtained, revealing average standard deviation of 2.76 cm in filtered SSH differences between platforms—validating both the system design and data processing methodology. This experiment successfully demonstrates the performance of calibration equipment, preliminarily verifies the effectiveness of ground-based calibration data processing techniques, and further confirms the technical viability of establishing an ocean altimetry satellite calibration site around Qianliyan islet.

Based on the massive teleseismic waveforms collected by the China Array II project, we investigate the 410 km and 660 km discontinuities (referred to as ‘410’ and ‘660’) beneath the northeastern Tibetan Plateau. After all of the 95747 radial receiver functions are stacked into each 0.5x0.5° grid, the P410s and P660s arrival times are Picked. Referring to the local 3-D tomographic model, the ‘410’ and ‘660’ depths are 416±0.6 km and 676±0.8 km, respectively, and the mantle transition zone (MTZ) thickness is ~260 km. Considering the remote effect of the subducted Indian Plate and Pacific Plate, we focused on the depressed two discontinuities. In particular, along the northeastern boundary of the Tibetan Plateau, the ‘410’ is confirmed as a dynamic barrier to hot asthenospheric flow, which escapes from the Tibetan Plateau and is obstructed by the rigid cratonic lithosphere in its surrounding area. The ‘660’ is obviously affected by cold anomalies that are delaminated or removed from the thickened lithosphere. In the western NCC(North China Craton), combining with the depressed ‘660’ and relatively larger P660s-P amplitude ratio, we speculate that a certain amount of water has accumulated in the lower MTZ, while the low Vs velocity around the 660 km depth may be related to melting. According to previous results, we propose a mantle convection model driven by the edge-derived convection of the subducted Pacific Plate. The cratonic lithosphere beneath the Ordos block may also undergo slow modification.

To better constrain the amalgamation of the East and West Cathaysia blocks, we deployed a short-period dense seismic array oriented nearly north-south in the southwestern Cathaysia block. According to the 997 teleseismic receiver functions recorded by 527 node geophones, we find that the Mohorovicic discontinuity (Moho) is slightly uplifted towards the coastal Cathaysia block. The most obvious feature is the high Vp/Vs ratio and deepen Moho beneath the Sanshui basin. Based on the common conversion point (CCP) migration images, we deduce that there may be distributed with the extension of the Gaoyao-Huilai deep fault, and it is supported by the offset of Moho and occurrence of the Mw 4.3 earthquake. Combined with other evidences, we further concluded that a weak suture zone is constrained beneath along the Zhenghe–Dapu and Gaoyao–Huilai deep faults, which may indicate the remnants of the amalgamation of the East and West Cathaysia blocks.

Gravity-matching navigation is one of the important means for the covert navigation of underwater vehicles. The production and application of gravity reference maps as core key technologies have a very significant impact on the accuracy of underwater navigation. Firstly, this paper adopts the factor analysis method to obtain the comprehensive results of nine characteristic parameters such as the standard deviation and roughness of the gravity reference map by setting a range sliding window. Secondly, the TERCOM algorithm is introduced to conduct simulation verification calculations within the sliding window. After comparing and verifying with the comprehensive results of the factor analysis characteristic parameters, the limitations of statistical methods in the evaluation of the adaptability of gravity reference maps are analyzed. Thirdly, intelligent processing methods such as the learning vector quantization neural network algorithm and the extreme learning machine are proposed. The characteristic parameters of some sliding window gravity reference maps and the simulation verification results of the TERCOM algorithm are used as training samples to predict the adaptability evaluation effect of underwater gravity navigation for other sliding windows. The results show that the prediction results are generally in good agreement with the simulation verification results of the TERCOM algorithm. Compared with the learning vector quantization neural network algorithm, the extreme learning machine algorithm exhibits superior performance in terms of classification accuracy and computational efficiency.