By establishing a BDS transmission reference control surveying model, the paper compares and analyzes the high-precision control surveying positioning performance differences between BDS-3/BDS-2 and BDS-3+BDS-2. Nine first-order control points of a project in Beijing and three IGS tracking stations in China and its surrounding areas were selected to establish a high-precision control surveying positioning network that supports both GPS and BDS-3/BDS-2 signals. Continuous observation data from three time periods(days 153-155 of 2023) were selected, and four schemes were designed for data processing. The positioning performance was compared and analyzed from two aspects: the transmission results of the initial reference and the adjustment results of control surveying. The results show that compared with GPS, BDS-3 and BDS-3+BDS-2 have only millimeter-level differences in N, E, U, horizontal, and point directions, while BDS-2 has differences ranging from millimeters to centimeters in the U and point directions, and only millimeter-level differences in the N, E, and horizontal directions. The measurement accuracy of BDS-3 is basically equivalent to that of BDS-3+BDS-2, while BDS-2 has lower accuracy than the other two, especially in the U direction.

This paper collects 227 marine gravity datasets obtained by Japan through ship borne surveys in its surrounding waters and the northwest Pacific. Statistical analysis, visualization mapping, and correlation analysis methods are used to analyze the gravity survey situation and data quality. This paper systematically analyzes the history, spatiotemporal distribution characteristics, and quality of gravity data surveys in Japan. The results show that ship measured gravity data has good consistency with GEBCO terrain data and DTU gravity model data, while the gravity data has a correlation of 0.98 and a root mean square error of 7.7 mGal with the DTU21. This paper establishes a trajectory intersection point difference model and analyzes the data measurement accuracy using intersection point difference error. The total crossover points are 73 979 with an crossover error of 11.85 mGal, the internal crossover point are 24 822 with an crossover error of 9.56 mGal, and the external crossover point are 49 157 with an crossover error of 12.85 mGal. The overall accuracy of the gravity data measurement accuracy is high, and the consistency is good.

This paper applies generative adversarial networks (GAN) to the denoising of GPS coordinate time series. The generator produces time series data, which is then distinguished from clean time series data by the discriminator. During training, the generator is iteratively optimized until the discriminator can no longer differentiate between the generated data and the real clean data, thereby achieving the denoising effect. Simulation results show that, compared with traditional methods such as WNNM, BiLSTM, and SSA, the GAN method achieves the closest correlation with the original noise in key indicators such as residual amplitude, residual spectral index, and velocity uncertainty, demonstrating more efficient denoising performance. Experimental results using real data further validate the effectiveness of the proposed algorithm in denoising actual GPS coordinate time series.

This paper employs VTEC data from the Jason-1/2/3 satellite series to analyze the accuracy of global ionospheric maps (GIMs) from temporal and spatial perspectives, and establishes corresponding correction equations using solar activity components, diurnal variation components, and seasonal variation components. The results indicate: 1) The residuals(G-J) between CODE GIMs and Jason series satellite data exhibit a quadratic function relationship with F_10.7, showing a 24-hour periodic characteristic in diurnal variation and a semi-annual variation pattern in seasonal changes. The correction equations can effectively amend the GIMs data. 2) The mean value of G-J reaches its maximum in the low-latitude regions of the Pacific and its minimum in southern Australia; the plasma transport within the equatorial anomaly leads to a bimodal feature in the median error of G-J; the relative error of G-J attains its maximum in the southern Atlantic Ocean, particularly in the marine areas off southern Africa.

The first arrival travel times of a deep reflection profile, approximately 30 km long, implemented along the northwest-southeast direction across the northern segment of the Tangshan fault in 2023 were inverted to obtain a detailed shallow velocity structure profile in the northern part of Tangshan. The velocity structure profile reveals that from 2.5 to 8.5 km along the survey line, the Cenozoic Era sediments are about 150 m thick and relatively uniform. The Fengtai-Yejituo fault is hidden at the survey line coordinate of 3.5 km, trending northwest, and F_2-1 fault is hidden at 8.5 km, trending southeast; there is a hidden bulge between these two faults that is low in the northwest and high in the southeast. From 8.5 to 15.2 km along the survey line, the Cenozoic Era sediments gradually thicken from northwest to southeast, with a maximum thickness of about 250 m, indicating that the Jinggezhuang depression is a gull-shaped Cenozoic fault depression. The Douhe fault is exposed at 15.2 km, trending northwest. From 15.2 to 24 km along the survey line, it is the Tangshan uplift, with only local areas having very thin Cenozoic Era sediments, and the P-wave velocity at the same depth is much higher than on both sides; there is a nearly vertical low-velocity zone under Weishan, extending at least 600 m downward, which is speculated to be the fault zone of the Tangshan-Weishan-Changshan south slope fault belt. From the survey line coordinate of 24 km to the end of the survey line, it is the northwestern part of the Kaiping depression, showing a regular basin edge morphology, with Cenozoic Era sediments of about 130 m. The Douhe fault and the Tangshan-Weishan-Changshan fault are active faults of the Quaternary.

Based on TEC data obtained from the CODE and electron density(N_e) data acquired by the CSES, the seismo-ionospheric perturbations prior to three M_S≥6.0 earthquakes in western China from 2020 to 2022(that is the 2020 Jiashi M_S6.4 earthquake, the 2021 Yangbi M_S6.4 earthquake and the 2022 Maerkang M_S6.0 earthquake) were analyzed. The ionospheric anomalies were found to be concentrated in 1 week before the earthquakes. The synchronization anomalies of CODE TEC and CSES N_e occurred 5 and 2 days before the Jiashi M_S6.4 earthquake, 7 days before the Yangbi M_S6.4 earthquake and 6 days before the Maerkang M_S6.0 earthquake. In addition, it is possible that these three strong earthquakes may affect the ionosphere through the geochemical and electromagnetic channels, as described by the lithosphere-atmosphere-ionosphere coupling(LAIC) model. There were earthquake precursor anomalies such as geochemical anomalies, water level and electromagnetic anomalies near the focal area in the 5 to 15 days before the earthquakes.

Anisotropy exists in the Earth's inner circle, and its genetic mechanism is different.Shear wave splitting can reveal the characteristics of anisotropic media at various depths and structures, providing crucial information for the study of deep Earth dynamics and earthquake prediction. This paper introduces the mechanism of anisotropy in the Earth's interior, summarizes the development of shear wave splitting methods, and the achievements and progress of study the anisotropy of the crust-mantle coupling model by shear wave splitting method.

This article collected seismic waveform data for events of magnitude M_L≥2.0 in Changzhi, Shanxi province, and its surrounding areas since 2009. The focal mechanisms of these events were determined using the Snoke first motion polarity and amplitude ratio method. Ultimately, 42 focal mechanisms were obtained for natural earthquakes with M_L≥2.4 and RMS≤ 0.45, alongside 6 for non-natural earthquakes. The results indicate that the focal mechanisms of natural earthquakes in the study area are predominantly strike-slip and normal strike-slip, primarily influenced by NEE-SWW compression and NNW-SSE extension. The Changzhi basin exhibits a complex and unique local stress field characterized by a nearly NS-oriented T-axes direction. The P-axes along the Wenwangshan fault follow an NEE-SWW orientation, while in other regions, NE-SW is the dominant direction, showing good consistency in fault plane solutions and high dip angles. The study also explores the focal mechanisms of non-natural earthquakes in the region. Mining-induced earthquakes are mostly normal faulting, while collapse events are reverse faulting. The stress axis characteristics of these non-natural events exhibit significant deviations, with the P-axes or T-axes showing large rotations and the angles between the two axes are about 180°, which is distinctly different from the natural earthquakes where the P-axis/T-axis are nearly perpendicular. These features can assist in distinguishing between different types of earthquakes.

Based on the mobile gravity data from Hebei province and its neighboring areas, we select the 2016-06-23 Shangyi M_S4.0, 2017-09-04 Lincheng M_S3.7, 2018-02-12 Yongqing M_S4.3, and 2019-12-05 Fengnan M_S4.5 earthquakes to analyze dynamic changes of gravity field. Combining with geological structure information, we investigate the relationship between seismicity and gravity changes. The results show that: 1) For earthquakes of approximately M4, significant pre-seismic changes of gravity field are observed, with notable positive and negative anomaly high-value areas and high-gradient zones, suggesting potential precursor information. 2) Earthquakes tend to occur near fault. The direction of contour lines of high-gradient zones of gravity field is mostly consistent with the orientations of major active fault in the region, indicating a close relationship between earthquakes occurrence, gravity changes, and fault structures. 3) The physical parameters of subsurface media are important for earthquake occurrence. Therefore, it is essential to integrate other disciplines for comprehensive assessments when conducting earthquake prediction.

Using the arrival time data of natural earthquakes from January 2009 to June 2023 in Shanxi and adjacent areas, the double-difference tomography method was employed to obtain the relocated catalog of the region, as well as high-resolution three-dimensional crustal velocity structure and velocity ratio structure. The tectonic environment for historical earthquakes of magnitude 6 or above in this area was discussed. The two-dimensional profiles of velocity and velocity ratio versus depth for historical earthquakes of magnitude 6 or above that passed through the southern part of Shanxi show that the 1303 Hongtong earthquake of magnitude 8 occurred on a gradient belt of high and low velocity anomalies, with a low-velocity anomaly beneath the earthquake, indicating that the ductile creep of the lower-middle crust can lead to localized stress and strain concentration in the brittle upper crust, triggering earthquakes. The earthquake is located in an area of low velocity ratio, and the Linfen basin has a low velocity ratio beneath it, with slightly higher velocity ratios on both sides of the mountainous areas, which is related to the process of crustal extension and thinning beneath the basin. Both the velocity and velocity ratio structures show that the structural characteristics beneath Luoyunshan piedmont fault are steep in the shallow part and gentle in the deep part, with the fault cutting extending to a depth of about 30 km, which is similar to the results of existing seismic reflection profiles and may be the reason for multiple earthquakes of magnitude 6 or above in this area. Most historical earthquakes in the southern part of Shanxi occurred near the gradient belt of high and low velocity ratios, which may be related to these areas being located at the boundary of the basin and mountain, where the crustal material composition changes more dramatically and is more likely to accumulate stress and strain, thus generating earthquakes.

In order to simultaneously improve the efficiency and reliability of point cloud plane segmentation, based on the multi-scale supervoxel and region growing algorithm, supervoxels are used as the growing units, and the voxel region growing algorithm is used to achieve fine point cloud plane segmentation. The results show that the proposed method has good segmentation effect on both indoor and outdoor point cloud data, which is superior to RANSAC, Khaloo and global energy optimization methods. Moreover, the Precision, Recall and F₁-score of the method in this paper are all higher than 0.90.

A constellation performance evaluation is conducted using the number of visible satellite and position dilution of precision(PDOP) of three low Earth orbit(LEO) constellations Hongyan, CentiSpace, and Hongyun in China. Simulated LEO data is combined with GNSS observation data from 12 evenly distributed stations to enhance precise point positioning(PPP). The performance enhancement effects of three LEO constellations on GPS/GLONASS/BDS/Galileo PPP are compared and analyzed in static and simulated dynamic modes. The results show that after the enhancement of Hongyan, CentiSpace, and Hongyun LEO constellations, the average static PPP convergence time of all stations is reduced by 64%, 77%, and 80%, the static PPP accuracy is improved by 33%, 36%, and 43%, respectively. The dynamic PPP convergence time is reduced by 67%, 76%, and 86%, the dynamic PPP accuracy is improved by 10%, 17%, and 16%, respectively. Overall, the PPP enhancement performance of CentiSpace and Hongyun LEO constellations is more significant compared to Hongyan constellation, and the enhancement performance is generally positively correlated with constellation size.

Based on hourly-resolution zenith tropospheric delay(ZTD) data from 35 GNSS stations in the Greenland region spanning the period from 2010 to 2021, combined with ERA5 reanalysis datasets and T_m model, precipitable water vapor(PWV) over the region was retrieved. Subsequently, the principal seasonal and diurnal variation characteristics, including annual, semi-annual, diurnal, and semi-diurnal cycles, were investigated. The results indicate that the GNSS stations in Greenland exhibit a certain degree of autocorrelation, with the summer season showing weaker autocorrelation compared to other seasons. The amplitude of the annual component ranges from 2 to 7 mm, while that of the semi-annual component ranges from 0 to 3 mm, with relatively minor interannual variations in their phases. The maximum values occur in summer, and the minimum values in winter. The diurnal component is only pronounced at a few stations, with amplitudes around 0.08 mm. After removing the annual, semi-annual, and diurnal components from the time series to obtain the residual time series, the maximum RMSE ranges from 1.30 to 3.65 mm, with an average RMSE of 2.08 mm. Notably, the RMSE values are relatively higher in the northern region and lower in the southern region.

To address the challenges of traditional hard-threshold methods in dealing with ambiguous boundaries when processing abnormal stations, this paper proposes a new method that treats station anomalies caused by tectonic movements and observational errors as gross errors and uses a membership function to construct an IGGIII equivalent weight function to mitigate the impact of abnormal stations. The new method incorporates fuzzy set theory and is an improved IGGIII robust estimation method based on the membership function of the fuzzy subset to which standardized residuals belong to gross errors(membership function IGGIII, MF-IGGIII). Firstly, the membership function of the fuzzy subset most affected by gross errors in standardized residuals is determined through fuzzy statistics; then, an equivalent weight function is constructed based on these membership function values, and a weight iteration process is performed. Simulation experiments and the fitting analysis of the GNSS velocity field in the Bohai rim area show that this method outperforms hypothesis testing, mean shift methods, and the IGGIII method in abnormal station detection, demonstrating strong capability in identifying abnormal stations.

This paper develops an integrated InSAR atmospheric delay correction method that combines external atmospheric data with topographic data. The basic approach involves introducing external atmospheric data to perform rough atmospheric delay correction on InSAR interferograms, followed by the establishment of a global correction model that links regional elevation to the interferometric phase, thereby suppressing the topography-related atmospheric delay components with long wavelength distributions. The interferogram is then processed in blocks, and a locally adaptive topography-related atmospheric delay error model is established for each block to achieve refined atmospheric delay correction for each sub-region. This study uses the Zagunao river basin, an area where landslides frequently occur, as a case study. Different atmospheric correction methods are applied to correct atmospheric delay errors in InSAR interferograms and to identify landslides. The results show that as the atmospheric correction progresses, the correlation between InSAR phase and topography significantly decreases, validating the effectiveness of the integrated atmospheric correction method. Furthermore, regional time series deformation analysis and landslide identification demonstrate that the integrated atmospheric delay correction method can effectively restore deformation signals from medium- and small-sized landslides, and significantly improve the accuracy of landslide boundary detection. Statistical analysis reveals that, compared to a single external atmospheric correction, the combined global topography-related atmospheric correction increases the number of identified landslides by 75%, and after further introducing local adaptive atmospheric correction, the number of identified landslides increases by an additional 33%.

This paper analyzes the orbit determination accuracy and orbit extrapolation accuracy under different gravity field models and finds that the accuracy is higher when the gravity field model order is 100 and 150 compared to when it is 50. In the reduced dynamic orbit determination of GRACE-C and GRACE-D, the 3D directional orbit determination accuracy of EGM2008 and Tongji-Grace02k can reach up to 22.6 mm and 24.0 mm, respectively, both of these gravity field models have better orbit determination accuracy than ITG-Grace03.In orbit extrapolation, Tongji-Grace02k has the highest accuracy, capable of reaching the sub-decimeter level, followed by EGM2008, while ITG-Grace03 has the lowest accuracy, both in decimeter level. Optimizing the random impulse parameters can improve the orbit extrapolation accuracy of the three gravity fields, with the optimization effect being more significant when the model order is 100 and 150 compared to when it is 50.

Based on the Sentinel-1A radar image data of the 2023 Jishishan M_S6.2 earthquake, we use D-InSAR technology to obtain the coseismic deformation field of ascending and descending orbits, use SDM inversion program to obtain the slip distribution of seismogenic fault, and use Coulomb3.3 program to obtain Coulomb stress changes of regional fault. The results show that the coseismic deformation fields generated by this earthquake are mainly uplifted, and the maximum LOS deformation is 6.8 cm for ascending orbit and 7.6 cm for descending orbit, and the optimal solution of seismogenic fault is 303° of strike, 52° of dip, and 89° of slip. The maximum slip is 0.5 m, which occurs at a depth of 11.89 km from the surface, and the rupture does not reach the surface. The cumulative seismic moment released was 1.48×10¹⁸ Nm, with a moment magnitude of M_W6.1. The Coulomb stress results indicate that the stress in the southern margin of Lajishan fault, the northwest section of north edge of western Lajishan fault, the northwest section of Daotang-Linxia fault, and the northwest section of north edge of western Qinling fault are in the state of obvious stress loading, and the above regions are more probable to have earthquakes in the next period of time, which need to be paid attention.

A multi-scale prediction model(referred to as C-TCN-A) based on complete ensemble empirical mode decomposition with adaptive noise(CEEMDAN) and temporal convolutional network-attention mechanism(TCN-Attention) algorithms is proposed, which can be effectively applied to missing data imputation and future trend prediction of GNSS elevation time series. The model first employs CEEMDAN for multi-scale decomposition of time series, then utilizes TCN-Attention for prediction and reconstruction of different scale components to obtain final results. To validate the model's performance, 12 observation stations were selected for 1-day and 5-day predictions, with comparisons made against multiple other models. Results demonstrate that in 1-day prediction, C-TCN-A reduces RMSE and MAE by 35%-40% and 36%-41% respectively while improving correlation coefficient R by 25%-29%. For 5-day prediction, it achieves reductions of 20%-26% in RMSE and 20%-28% in MAE, with R increasing by 26%-33%. To verify the model's universality, C-TCN-A was applied to 99 stations from the crustal movement observation network of China(CMONOC) for 1-day and 5-day predictions. Results indicate generally favorable RMSE and MAE metrics with concentrated error distribution, where most errors remain below 4 mm. Spatial analysis reveals regional performance differences, with optimal results achieved in the northwestern region.

Based on the PWV time series data inverted from GPS during 2010-2018 and the PWV data calculated from the ERA5 reanalysis data for the same period, a combination of the generative adversarial networks(GAN) model and the Transformer neural network model in deep learning was employed to achieve short-term forecasting of PWV in Greenland using GPS-PWV data. The prediction results were evaluated using the ERA5 data from 2019. The results show that the model performed well in most areas, with a root mean square error(RMSE) better than 4.5 mm and a correlation coefficient greater than 0.7. The correlation coefficients in spring, autumn, and winter were all above 0.5, while in summer, the correlation coefficients on some dates were slightly lower due to severe weather changes. This method is capable of predicting the spatial distribution and temporal variations of PWV in Greenland.

GNSS-R(global navigation satellite system-reflectometry) technology has been widely verified as an effective means of monitoring ocean tide levels, but the commonly used LSP(lomb-scargle periodogram) spectral analysis method still has issues with low precision and time resolution in storm surge monitoring. This paper, based on observational data from the HKQT station in Hong Kong, China, uses a non-linear fitting method to conduct inversion studies on the storm surge event of Typhoon "Mangkhut" in 2018. By combining wind speed change data during the storm surge period, the paper compares the performance of spectral analysis and non-linear fitting methods in tide level inversion. The results show that the measurement accuracy using the non-linear fitting method is better than 8 cm, with a correlation coefficient of 0.99 compared to the observational data from tide gauge stations. The tide level representation is smoother and more continuous than that of the spectral analysis method, effectively improving monitoring accuracy and time resolution, and providing more reliable technical support for storm surge disaster monitoring.

In order to understand the current surface deformation characteristics and stress state of Shanxi reservoir area, we obtain the cross-fault deformation rate field in the study area based on 57 Sentinel-1 radar images from 2022 to 2023 using SBAS-InSAR technology, and analyze the influencing factors of surface deformation. The results show that the crust in the study area is overall in a state of strain accumulation, and the short-term surface deformation near reservoir area is mainly controlled by water storage. The seismogenic fault is still accumulating strain in the inter-seismic phase, and continuous monitoring of surface deformation in reservoir area should be carried out to provide a basis for seismic hazard assessment.

To address the challenges of insufficient real-time interaction capabilities and limited functionalities in wireless node seismometers during geophysical exploration and seismic monitoring, this study designs an Android-based integrated platform for node seismometer monitoring and field deployment. The platform leverages bluetooth low energy(BLE) technology and implements a custom encrypted wireless communication protocol to enable data exchange and device control between mobile terminals and node instruments. Key functionalities include real-time visualization of single/triaxial seismic velocity signals, status monitoring, and synchronized configuration of single or multiple devices. Additionally, the platform integrates ultra-high frequency(UHF) RFID technology, QR code scanning, and electronic maps to achieve rapid field deployment of seismic node arrays. SQLite databases and a local file system are employed to ensure reliable recording of survey lines, parameter configurations, and system log management. Experimental results demonstrate that the platform can enhance the efficiency of field geophysical surveys and mobile seismic monitoring.

Based on continuous waveform data from the M_S4.7 earthquake in Ar Horqin Banner on October 15, 2021, for three months post-earthquake, machine learning methods were utilized for picking earthquake phases and associating them. The preliminary machine learning-based earthquake catalog constructed includes 386 seismic events, which is 17 times the number of events in the manual catalog of the Inner Mongolia seismic network for the same period. Subsequently, using the P/S phase arrival time information from the event waveforms, a double-difference location method was applied to precisely locate the aforementioned aftershocks and study the seismogenic structure of the earthquake. The results indicate that the aftershocks of the M_S4.7 earthquake in Ar Horqin Banner have two main directions of distribution, nearly NW and nearly NEE, within a 1-5 km range around the mainshock. Based on the relocation results and combined with linear geological structures on the topography, it is suggested that there exists an unidentified hidden faults. The distribution of the 4.7 magnitude earthquake and its aftershocks is primarily controlled by the nearly NW-oriented hidden faults and the nearly NEE-oriented structures.

Aiming at the problems of poor positioning accuracy, slow convergence speed, and large influence of clock drift in the case of single-satellite positioning methods, a joint pseudo-ranging/Doppler positioning model with clock-difference correction is proposed, which combines the mathematical model of clock-difference with the pseudo-ranging observation equations and Doppler observation equations, and eliminates the influence of the change of the receiver's clock-difference on the positioning accuracy through the simultaneous estimation of clock drift by the mathematical model of clock-difference and the Doppler observation equations. The proposed method is validated in a simulation scenario, and the results show that the optimal positioning accuracy of the pseudorange/Doppler joint positioning with clock difference correction can reach 219 m under different working conditions, which is 59.4% higher than that of the Doppler localization method; when the pseudorange measurement error is 1 m, the positioning accuracy can be up to 169 m, and the convergence time is around 300 s; when the frequency measurement error is 0.5 Hz, the positioning accuracy can be around 140 m.

In this study, natural and non-natural seismic events in Guangdong and surrounding areas were selected as the research objects, and the typical physical characteristics of P waves and S waves in frequency domain were extracted from seismic waveform data. We used the feature combination optimal solution algorithm to input the best feature parameters into the support vector machine model for sample training, and identified the non-natural earthquakes in Guangdong and surrounding areas. The test results showed that the accuracy of earthquake classification is 99.3%. In addition, the non-natural seismic identification module based on support vector machine was developed and connected to the daily cataloging system of Guangdong seismic network, which realized the quasi-real-time automatic identification of seismic event types. The application results showed that the recognition accuracy of 130 manually cataloged seismic events was 96.9%.

For the five ultra-high-degree Earth gravity field models with a degree of 2 190, namely EGM2008, EIGEN-6C4, GECO, SGG-UGM-2, and XGM2019e_2159, which have been published internationally, a study on quasi-geoid refinement was conducted using the Shanxi survey area as an example. First, the accuracy performance of five models in Shanxi area was compared and analyzed using actual GNSS/leveling data. Then, based on the remove-restore technique, the residual height anomalies after removing the results of five ultra-high-degree gravity field models were fitted to the quasi-geoid using the multiquadric function method. A contour line-based method for selecting multiquadric function nodes was proposed, and the fitting accuracy was compared and analyzed. The results show that: 1) The accuracy distribution of five Earth gravity field models in Shanxi area is consistent, with larger errors mainly distributed in the high mountain areas in northern Shanxi. The XGM2019e_2159 model has the highest accuracy with a mean error of 9.1 cm, while the EGM2008 model has the lowest accuracy with a mean error of 11.3 cm. 2) The accuracy of five ultra-high-degree gravity field models does not significantly affect the final quasi-geoid accuracy. Among them, the quasi-geoid derived from considering the EGM2008, EIGEN-6C4, and SGG-UGM-2 models has the highest external consistency accuracy with a mean error of 5.0 cm. The quasi-geoid derived from XGM2019e_2159 model with the highest accuracy has the lowest external consistency accuracy with a mean error of 5.5 cm.

This article is based on the kinematic GNSS observation from the 13th Chinese Arctic Ocean scientific expedition, which marked China's first arrival at the North Pole. It compares and analyzes the observation quality of different signal from BDS and GPS in terms of carrier-to-noise ratio, multipath effects, pseudorange noise, ionospheric delay rate of change, and evaluates their kinematic positioning performance. The results show that the BDS's visible satellite count is still maintained at 8 to 14 close to the North Pole, and that the PDOP value is superior to that of GPS. In the Arctic region, the RMS of multipath combination observation for BDS is around 0.2 m. The RMS of multipath combination observation for B1C and B2a is smaller than the B1Ⅰ and B3Ⅰ signal, but their pseudorange noise is higher. The results of kinematic pseudorange positioning show that the positioning accuracy of BDS is comparable to the GPS, with the B1C/B2a ionosphere-free combination yields better positioning performance than the B1Ⅰ/B3Ⅰ combination.

Taking the southern section of the Jiayuguan fault as the research subject, the morphology of the hidden segment of the fault was determined through shallow artificial seismic exploration. Based on remote sensing image interpretation and field geological surveys, the fault was found to be exposed at the surface at the southern end of the Jiayuguan fault, forming an anticline fault scarp. Through aerial photogrammetry, combined with dating tests, it was determined that the fault has been active since the late Pleistocene. Using high-precision topographic data, the height of the fault scarp was obtained, and combined with the corresponding geomorphological age, the vertical slip rate of the southern section of the Jiayuguan fault was estimated to be 0.03±0.01 mm/a.

Using the FOCMEC method, we calculated the focal mechanism of 89 earthquakes with magnitude between 2 and 3.5(2≤M_L≤3.5) in the middle and southern section of Weixi-Qiaogou fault and its surrounding areas(99.5°-100.5°E, 25.0°-26.5°N) from 2018 to 2022. Combining with the collected focal mechanism results of 132 earthquakes with magnitude greater than 3.5(M_L > 3.5), we inverted the regional stress using the tensor damping method to obtain a detailed tectonic stress field with a resolution of 0.25°×0.25° of the study area. We analyzed the distribution characteristics of focal mechanism solutions and stress field, and discussed the stress state of the middle and southern section of Weixi-Qiaogou fault and its surrounding areas. The results show: 1) The types of earthquake focal mechanisms in the study area are mainly strike-slip, followed by normal fault type. 2) The study area is subjected to NS-directed compression and EW-directed extension, with the overall principal compressive stress orientation being NNW-SSE, showing a clockwise rotation trend. The stress tensor factor R value varies between 0.02 and 0.39, indicating that the study area is generally characterized by compressive stress. 3) The stress field direction of Jianchuan-Dali section of Weixi-Qiaohou fault is mainly NNW-SSE, with a small amount of nearly NS direction, and the stress field is mostly horizontal, with a smaller R value. The Dali-Weishan section has a stress field direction of NNE-SSW and NS, and the stress field is mainly vertical, with a larger R value.

Previous ZWD models over China only consider the effects of elevation, latitude and meteorological parameters, without taking into account the impact of monsoon climate and ocean water vapor transport on ZWD estimation. To solve this problem, we take bias correction as the breakthrough point, analyze the spatial distribution of RMSE and bias of ERA5-ZWD estimation value obtained by the ERA5 data integration method and inversion method over China from 2016 to 2019. Then, the regional bias correction model over China based on RF_Adaboost neural network is established using the ERA5 and radiosonde data from 2016 to 2018. The results show that the bias of ERA5-ZWD estimation value in 2019 is significantly reduced after correction, and the RMSE is significantly reduced in the eastern coastal areas and southern regions of China.

Aiming at the requirement of high-precision time transfer between kinematic users and the limitation of PPP time transfer relies on real-time precision orbit and clock products, we study the kinematic-to-kinematic single-difference carrier phase time transfer method for real-time estimation of base station coordinates, and carry out static simulated dynamic and measured kinematic tests to evaluate the performance of single-difference carrier phase time transfer method. The results show that standard deviations of static simulated dynamic zero-baseline and non-zero baseline time transfer are 0.034 ns and 0.053 ns, respectively, and the frequency stability is 9.49×10^-16/30 000 s and 1.85×10^-15/30 000 s, respectively. The standard deviation of measured kinematic non-zero baseline time transfer is 0.095 ns, and the frequency stability is 8.37×10^-14/300 s, which verifies the feasibility of algorithm in actual motion scene. The GPS kinematic-to-kinematic single-difference carrier phase time transfer has low cost and is easy to implement. The clock solution with sub-nanosecond accuracy can be realized by using GPS observations and broadcast ephemeris, which provides a key technology for short-distance, kinematic and high-precision time transfer.

Based on the waveform data and seismic phase reports from the Xinjiang regional digital seismic network, the focal mechanism solution of Aheqi M_S5.2 earthquake and some aftershocks are inverted using the CAP method. Meanwhile, the double-difference localization method is used to relocate the earthquake and its sequence. The results show that the strike, slip and rake are 259°, 44°, and 90° for nodal plane I, and those are 79°, 46°, 90° for nodal plane II, respectively, with a moment magnitude of M_W4.76, and a depth of moment center of 5 km, which suggests that the earthquake is a reverse-type event. The relocation results show that Aheqi M_S5.2 earthquake sequence spreads linearly in the NW direction and is perpendicular to the fault strike, and the depth is concentrated in 3-6 km. Based on this, we comprehensively analyze the historical seismic mechanism solution, geological and tectonic background, and conclude that the Suogedangtawu fault, which is located at the root of Keping thrust tectonic, is the seismogenic structure of this earthquake. This study can provide a certain understanding of the seismic mechanism of strong earthquakes in the contact zone between south Tianshan orogenic belt and Keping thrust tectonic, and provide reference for regional earthquake trend analysis.

Utilizing the Yunnan small earthquake monthly catalog and seismic wave data recorded by the seismic network, we calculated the correlation coefficients of spectral amplitudes for Yunnan M≥5.0 earthquake sequences since 2008. A comprehensive analysis of traditional seismological parameters, including the h and b values, for different types of earthquake sequences revealed that the correlation coefficients of spectral amplitudes for foreshock type seismic sequences are significantly higher than those for earthquake swarm and mainshock-aftershock type sequences. Moreover, the range of variation is relatively small, with values exhibiting a concentrated distribution. In contrast, traditional seismological parameters show a more concentrated b value and a wider distribution range for the h value. Analysis of the correlation coefficients of spectral amplitudes for 8 typical foreshock type earthquake sequences indicates a good correspondence between changes in the correlation coefficients of spectral amplitude and the magnitude intensity of foreshock type earthquake sequences. The analysis suggests that a high correlation coefficient of spectral amplitude is indicative of high regional stress levels, and fluctuations in the correlation coefficient of spectral amplitude may be influenced by the loading and unloading of seismic stress.

By conducting a comprehensive analysis of two shallow seismic profiles, VSP-measured P-wave velocity data, and one drilling joint geological profile from the Shenqiu depression in the southern north China basin, this study investigates the geometric characteristics and discernible upper fault depths of a series of negative flower-like structures in the shallow part of the strike-slip fault zone. The results indicate that the fault displaces the Quaternary strata upwards, with the discernible upper fault depth on the shallow seismic exploration profile being approximately 60 meters, and the discernible upper fault depth on the drilling joint geological profile ranging from 38.6 to 40.1 meters, suggesting that the fault displaces the middle Pleistocene strata. The exploration findings reveal that the fault is a set of left-lateral strike-slip faults arranged in a NWW direction, resembling a line of geese. This indicates that the southern north China basin has experienced NW-directed strike-slip shearing during the Quaternary, suggesting that the NW-directed tectonic system, controlled by the Qinling orogeny, has remained active since the Quaternary. This has significant implications for analyzing the evolution of the basins in the eastern plains of the north China block.

This study employs time-series InSAR technology to extract the interseismic surface deformation field along the Anninghe-Zemuhe fault zone on the eastern margin of the Sichuan-Yunnan rhombic block. We further invert the interseismic slip rates and locking depths of the fault system. Key findings include: the cross-fault InSAR deformation velocity gradient along the Anninghe fault increases progressively from ~2 mm/a in the northern segment to ~2.5 mm/a in the southern segment, whereas the Zemuhe fault exhibits a relatively smaller gradient of ~1.8 mm/a.Slip rates along the Anninghe fault vary spatially: ~2.8 mm/a at the northern Shimian segment, ~4.0 mm/a at the central Mianning segment, and ~3.2 mm/a at the southern Xichang segment. The Zemuhe fault shows a decreasing slip rate from ~3.1 mm/a in the northern segment to ~2.6 mm/a in the southern Ningnan segment.Locking depth analysis reveals maximum values (~37.8 km) beneath the Xichang segment, gradually shallowing northward to ~5.0 km at Shimian and southward to ~13.2 km at Ningnan.These results demonstrate that the Xichang segment, characterized by higher slip rates and deeper locking depths, exhibits enhanced seismic potential, consistent with its historically dense seismicity. This spatial correlation between geodetic deformation patterns and seismic activity provides critical insights into strain accumulation processes within this active tectonic boundary.

To address the challenges of excessive noise points and weak effective signals in satellite laser ranging(SLR) echo data, which hinder accurate and rapid signal identification, this study proposes a composite real-time signal identification method. The method integrates an improved traditional histogram-based approach with the Graz fast filtering algorithm, optimizing both identification accuracy and processing efficiency. A simulated platform was established to replicate signal generation processes, preliminarily validating the algorithm's advantages. Experimental validation using measured data(1 ms per data point) demonstrated that the proposed algorithm achieved a false detection rate of 8.71%, significantly lower than the 32.71% and 43.52% rates of two conventional secondary filtering algorithms, while maintaining comparable missed detection rates(about 10%). Post-processing analysis of 1 million echo datasets(100 000 echoes per satellite for 20 satellites) revealed an average computation time of 4.31 s, outperforming the conventional algorithms(7.28 s and 12.45 s).

The epicenter of 2022 Honghe M_S5.0 earthquake is located near the southern section of Red River fault zone, which consists of two nearly parallel faults: the Bolumu-Maocaoping fault and the Nanhun-Nabing fault. The Nanhun-Nabing fault is an active fault in the late Pleistocene, and significant water system dislocation deformation exists in the earthquake area. The field investigation after earthquake shows that a 1.2 km long surface rupture appeared on the ridge between Nanhun river and Nanchu river, and its distribution characteristics are consistent with the linear topography of Nanhun-Nabing fault. The deformation properties exhibited by the surface rupture in this area are consistent with the motion characteristics of earthquake rupture. Combined with the focal mechanism solution, it is believed that the Nanhun-Nabing fault is the seismogenic structure of Honghe M_S5.0 earthquake.

Based on the Sentinel-1 ascending and descending orbit images from 2014 to 2023, we use the time network orbit error correction method considering long-term structural rates to remove orbit errors, and the external GACOS atmospheric data and public main image superposition method are combined to remove atmospheric delay errors, obtaining high-precision and high-density InSAR interseismic velocity fields along Xianshuihe fault, revealing the fault movement characteristics dominated by left-lateral strike-slip. We calculate the fault-parallel velocity from InSAR data, which shows that there is a significant difference in the fault-parallel rate on both sides of far-field fault, about 8-11 mm/a. We also obtain the high-precision three-dimensional velocity field using GNSS data, and calculate the maximum shear rate strain field. The results show that the shallow creep movement is significant between Zhuwo to the middle of Kangding segment. Among them, the shear strain in the Songlinkou to the middle of Kangding segment is the strongest, with a maximum magnitude of 0.6 ustrain/a and a maximum creep rate of 7.0 mm/a. This study is helpful to understand the interseismic deformation and creep characteristics and provide high-quality data for interseismic coupling model inversion and earthquake risk assessment.

This paper takes the Earth rotation parameters(ERP) obtained by each individual measurement means as research data, and outputs the processing results in the time domain and frequency domain respectively. Then the index parameters obtained from each analysis are compared with the data analysis results obtained by joint calculation in international Earth rotation service(IERS). The results show that the time-varying characteristics of ERP obtained by various measurement methods are different.

Based on observation data from 77 GNSS stations worldwide, this study systematically evaluates the global applicability of four tropospheric delay mapping function models(GMF, NMF, VMF1, VMF3) and their impact on the accuracy of precise point positioning(PPP). The zenith tropospheric delay(ZTD) for each station was obtained using the PRIDE PPP-AR software. With the ZTD products released by the Center for Orbit Determination in Europe(CODE) as a reference, a comparative analysis of model performance was conducted across geographical zones(low/medium/high latitudes, land/ocean, and altitude gradients). The results indicate that the existing tropospheric delay mapping function models exhibit poorer accuracy in low-latitude, low-altitude, and oceanic regions. The VMF series mapping function models perform better in addressing differences arising from changes in altitude and latitude, and both the GMF and VMF series models show significant correction effects for oceanic stations. In terms of positioning accuracy in the U direction, the GMF, VMF3, and NMF mapping function models perform best in low-latitude, medium-latitude, and high-latitude regions, respectively. Overall, the GMF and VMF series mapping function models demonstrate superior performance in global PPP data processing.