To objectively evaluate the accuracy of TPXO series ocean tide models for the eastern China sea(ECS), we use the latest FES2014b and EOT20 as reference models. The assessment is performed by computing the root mean square error(RMSE) of the M₂ vertical ocean tide loading(OTL) displacements and the root sum square(RSS) of the 8 principal tidal constituents based on the GPS-observed M₂ vertical OTL displacements and tide gauge observations from the evenly selected 22 GPS sites and 65 tide gauges in the coastal areas, respectively. The results show that: 1) In the whole ECS, EOT20 is the most accurate model with RMSE of 0.41 mm and RSS of 11.1 cm, while the accuracy of FES2014b is slightly lower with RMSE of 0.43 mm and RSS of 11.4 cm. 2) Along the coast of eastern China and the western Korean Peninsula, there are large differences between TPXO models and FES2014b, and the RSS with tide gauge observations are 2-6 times as much as that of FES2014b and EOT20. 3) Both TPXO9_Atlas and TPXO8_Atlas agree better than other models with the M₂ vertical OTL observations in the Ryukyu Islands, and the two models are suggested for the local correction of OTL displacements.

We comprehensively use InSAR and machine learning technology to evaluate landslide susceptibility in Jinyang county, Sichuan province. The data set is updated by interpreting landslides. Based on 12 evaluation factors, we use three models including random forest(RF), support vector machine(SVM) and extreme gradient boosting(XGBoost) for training in Python environment to complete landslide susceptibility mapping. We use ROC curve to verify prediction performance. We optimize the negative samples, obtain the landslide susceptibility evaluation results after sample optimization using machine learning and update the landslide susceptibility results using surface LOS deformation rate. The results show that the three machine learning models have good zoning effect, and the mapping effect of XGBoost model is best. The accuracy of XGBoost model after sample optimization is highest, and the AUC value reaches 0.95. The surface deformation rate obtained by SBAS-InSAR can reduce zoning errors and give timeliness to landslide susceptibility evaluation.

We propose a method for ground deformation monitoring based on distributed scatterer InSAR(DS-InSAR). The method employs the HTCI algorithm for homogenous pixel identification, utilizes eigenvalue decomposition for phase optimization, determines distributed scatterer(DS) based on spatiotemporal coherence, and establishes a relationship model between DS phase and deformation for time series surface deformation inversion. We use 50 scenes of Sentinel-1A images to obtain spatiotemporal distribution information of ground deformation in Jiangbei region of Nanjing from October 2021 to October 2023. The results show that: 1) The correlation coefficient between DS-InSAR results and PS-InSAR results is 0.731, and the point density increases by 6.22 times. DS-InSAR can more completely reflect the spatiotemporal surface deformation of the study area. 2) DS-InSAR is in good agreement with the measured leveling data, with a maximum error of 5.6 mm, an average error of 2.6 mm, and a root mean square error(RMSE) of 3.0 mm. 3) The geological structures, urban development, and rainfall are the main influencing factors causing ground subsidence.

Based on the mobile Beidou deformation monitoring system at Xiluodu hydropower station, we per- form the horizontal deformation simulation experiment. The static differential positioning, post-processed kinematic positioning and precise point positioning methods are employed to compute actual displacements and evaluate accuracy. The results indicate that the accuracy of single BDS and GPS+BDS dual systems is consistent. The static differential method has the highest accuracy, with the external coincidence accuracy of dual systems and single BDS better than 0. 5 mm and 0. 7 mm, respectively. The baseline differential method can effectively eliminate interference from dam area water vapor, ionospheric and multipath errors through 24 hours long-term observations. The maximum errors of PPK for dual systems and single BDS are 0.5 mm and 1 mm, respectively, while under dynamic PPP are 1. 7 mm and 1 mm, respectively. This shows thatPPK and PPP can also achieve deformation monitoring results close to 1 mm, demonstrating significant application potential.

Based on the Sentinel-1A image data covering the epicenter, we use D-InSAR to calculate the surface coseismic deformation field of Xinjiang Wushi M_W7.0 earthquake. We use the quadtree method to downsample the coseismic deformation field, and optimize the geometric and physical parameters of the fault by using the downsampling data as constraint conditions. The results show that the maximum uplift values of ascending and descending orbits are 72 cm and 39 cm, respectively. The seismogenic fault is within the Maidan-Shayilamu fault, which is dominated by thrust and has a small amount of left-lateral strike-slip. The fault strike is 230°, the dip is 67°, and the slip angle is about 45°. The maximum slip on the fault plane is 3.53 m, the seismic moment is 3.78×10¹⁹Nm, and the calculated magnitude is M_W7.02. The results of Coulomb stress show that the Tuoshigan fault, Kuokeshale fault, Dashixia fault, Kurukeyuzumu fault, and northern Kuqi fault are all in the stress loading region, on which we need to pay more attention in the future.

Addressing the under-quantified crustal deformation characteristics and the unclear stress-strain coupling relationship of the Ordos block, this study employs a spherical least squares collocation model to calculate the characteristic strain field of the study area's crust and inverts the principal stress distribution using seismic source mechanism data. The results indicate that crustal deformation is primarily concentrated along plate boundaries and within fault basins, with less deformation within the Ordos block itself. Notably, at the junction of the northeastern Tibetan plateau and the Alxa block, the crustal deformation is particularly intense, characterized by strong compression along the plate boundary, with the main deformation mechanism being a coexistence of NW-SE compression and NE-SW extension, with a maximum principal compressive strain rate exceeding 0.05 μstrain. The crust in the study area is under a relatively uniform tensile stress environment, with the direction of the maximum principal stress being nearly horizontal and pointing towards SEE, aligning with the direction of the principal strain in the corresponding area. The minimum principal stress direction is closer to the direction of the principal compressive strain.

We use the precise clock offset data released by IGS to analyze the key performance indicators of six GPS-Ⅲ satellite clocks that have been launched and operated in orbit, including frequency accuracy, frequency drift rate, and frequency stability, and compare them with the previous GPS clocks. The results show that rubidium clocks carried by GPS-Ⅲ are generally stable in operation and have good data quality, which is related to the improvement of anti-interference ability. There is no significant change or difference in time frequency performance, which is basically consistent with the previous generation Block ⅡF rubidium clocks. The frequency stability of GPS-Ⅲ rubidium clocks are better, which helps to improve the accuracy of PNT services. The research can provide reference and guidance for the upgrading and transformation of other GNSS system satellites.

On the basis of effectively handling the gross errors of landslide monitoring data and fully considering the characteristics of landslide monitoring data, we develop a deep learning landslide displacement prediction model combining time series decomposition and similar component reorganization. First, we deal with the significant gross errors of landslide time series monitoring data using the isolation forest algorithm, and then comprehensively analyze its smoothness, autocorrelation, and normality to determine the optimal length of input feature sequence. Second, the non-stationary landslide monitoring data are decomposed into multiple smooth time series using the ensemble empirical mode decomposition(EEMD) method, which is then classified into three types combining the sample entropy and K-means algorithm, namely high, medium, and low frequency. Finally, comparing the prediction accuracy of different neural networks, the prediction models suitable for three types of time components are constructed respectively, and then the prediction results are superimposed to realize the high-precision prediction of landslide displacement. The testing results of Beidou/GNSS monitoring data of typical landslide body in experimental area show that the combination prediction model proposed in this paper has a better applicability to the landslide monitoring data containing significant gross errors, and can significantly improve the prediction accuracy of landslide displacement compared with single and existing combination models.

We focus on the complex characteristics of groundwater level data, including nonlinear trends, seasonal fluctuations, and random disturbances, and introduce the Prophet time series prediction model developed by Facebook. The aim is to use its nonlinear trend capture, seasonal fluctuation analysis, and flexible response ability to outliers and data missing to significantly improve the accuracy of groundwater level anomaly identification. Through observation data from Beilin district seismic station in Suihua city, Heilongjiang province, it is shown that the Prophet model performs well in capturing dynamic characteristics of time series data and can effectively identify anomalies. The high fitting accuracy and predictive ability of adjusted model have been confirmed, with low prediction error and high determination coefficient. In addition, the model identifies water level anomalies related to earthquakes in earthquake prediction, providing a new perspective for earthquake precursor research. This study demonstrates the effectiveness of Prophet model in processing complex time series data, providing a new tool for earthquake prediction.

We lay a shallow seismic exploration line L1 with a length of 10.77 km extended southward across Serteng mountain piedmont fault. The results show that the Sertengshan piedmont fault is clearly visible on the profile, and the main fault has bifurcations in the upper part, consisting of faults F_P1.1 and F_P1, both of which are normal faults with an apparent inclination towards the south. Combined with geological and geomorphological surveys, the latest active age of the F_P1.1 fault is Holocene. We carry out a composite drilling geological section for the fault F_P1 of the Serteng mountain piedmont fault and distinguish two faults, Fa and Fb. Based on the results of optical stimulated luminescence dating, the faults Fa and Fb are Holocene faults and the latest active age is later than 2.5±0.6 ka BP. The Serteng mountain piedmont fault has a forked structure near the surface, which reflects the multiple activities of the fault in the late Quaternary.

Early research on broadband seismometer azimuth mainly based on the P-wave particle polarization principle and calculates the angle corresponding to the minimum value of P-wave energy on the lateral component to obtain the angle between the north-south direction of seismometer and the geographic north pole. In addition, the elliptical motion characteristics of Rayleigh waves can be used to estimate the seismometer azimuth of stations with azimuth deviation. We estimate the seismometer azimuth deviation of 20 stations of CENC based on the two different methods. The results show that the azimuth deviation calculated by the two methods is in good agreement, indicating that Rayleigh wave analysis can be appropriately added in future seismometer azimuth detection.

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.

We propose an adaptive stochastic model for low-cost receiver precise point positioning(PPP) in complex environments. The model improves PPP performance by adaptively adjusting the weight ratio of pseudorange observations and carrier phase observations of all GNSS satellites in a single epoch. We take the Hexinxingtong UM982 low-cost GNSS receiver to conduct PPP tests in three complex environments, including tree shade, high buildings and glass walls. The static PPP results show that the positioning accuracy of adaptive stochastic model is improved by 24%, 45% and 50% in three complex environments, respectively, and the convergence time is shortened by 49%, 27% and 24%, respectively, compared with the traditional empirical weighted stochastic model. The kinematic PPP results show that the positioning accuracy of adaptive stochastic model is improved by 35% in complex environment.

Using precise leveling measurement data and a modified dip-slip displacement model, we systematic analyze the vertical movement characteristics of each section of the northern margin fault of western Qinling mountains. The results show that the northern margin fault of western Qinling mountains is undergoing a composite deformation mechanism of left-lateral strike-slip and thrust compression, and the activity varies among different sections. The vertical dip-slip rate increase from 0.24 mm/a in the western section to a maximum of 2.31 mm/a in the eastern section, and then decrease to 1.51 mm/a. The inverted locking depths are consistent with the relocation depths of small earthquakes, which indicates that there are different locking states in each section. Combining seismic activity, the Tianshui-Baoji section has the highest earthquake risk.

GNSS technology is widely used in landslide monitoring, but it is difficult to install monitoring equipment in complex high-risk landslide environment. UAV-dropped is expected to realize unmanned deployment of monitoring equipment. In view of the problems of UAV-dropped endurance and terrain threat in complex environment, the path planning of UAV-dropped is particularly critical as the basic mission. In this paper, the path planning problem of UAV-dropped in complex mountainous area is studied in three aspects: 3D real map construction of geological disaster area, cost function design and flight path planning algorithm. In addition, whale optimization algorithm based on adaptive weight and Levy flight strategy is applied to the flight path planning of UAV-dropped. Taking Hongyanzi landslide in Hanyuan county, Sichuan province as the study area, the path planning of UAV-dropped GNSS monitoring equipment was realized.

We use ascending and descending orbit data of Sentinel-1A satellite to obtain high-precision coseismic deformation fields of Jishishan M_S6.2 earthquake using differential interferometry technology, and employ SBAS-InSAR technique to acquire cumulative deformation time series in the area near epicenter over the past six months. The results show that surface deformation is primarily uplift, with the maximum LOS coseismic displacements of about 6.8 cm and 7.3 cm for ascending and descending orbits, respectively. The rupture mainly occurred at depths ranging from 7 to 15 km underground, with a maximum slip of approximately 0.55 m. Within two months after the earthquake, there is an expanding trend of uplift deformation in the near-field and northwest side of the epicenter. We conclude that the Jishishan earthquake trended northwest, dipping northeast, and the seismogenic fault belongs to the hidden branch fault on southeast side of the southern margin of Lajishan fault zone. The large-scale sudden deformation after the earthquake may be related to pore pressure release, and the surface stability needs further observation.

Based on the observation data from 163 GPS continuous stations in Qinghai-Xizang plateau and adjacent areas from 2010 to 2020, we solve the GPS vertical coordinate time series. Using the global loading grid data provided by GFZ, the environmental loading displacements are calculated by double cubic linear interpolation method, and the GPS vertical time series are corrected. The results show that the hydrological loading has the greatest influence on GPS station displacement in the study area, which is larger in the southern stations, with a RMS of 9.45 mm(MUET site). By comparing the changes of weighted root mean square(WRMS), annual term amplitude and velocity uncertainty before and after environmental loading correction, it is found that the environmental loading correction is able to weaken the nonlinear variations of vertical time series of most GPS stations in Qinghai-Xizang plateau and adjacent areas and it can accurately improve the velocity accuracy of most GPS stations.

To reduce the positioning errors of global navigation satellite system(GNSS) in complex environments, we propose a method that combines high-precision points with distance intersection to accurately estimate the coordinates of an undetermined point. The observation equation is constructed as a nonlinear Gauss-Helmert model. To address the nonlinearity within this model, we introduce a back-propagation(BP) neural network for auxiliary processing. Compared with the traditional linearization methods, the BP neural network can effectively fit complex nonlinear functional relationships. The simulation experiments and actual measurement results show that this method can significantly reduce the impact of complex environments on positioning accuracy, and improve the positioning accuracy in E, N and U directions by 78.1%, 72.8%, and 79.2%, respectively.

Aiming the issue of reduced accuracy in sea surface height inversion using global navigation satellite system interferometric reflectometry (GNSS-IR) due to elevation angle deviation, a correction method for elevation angle deviation based on the ionospheric region is proposed. To verify the reliability of the correction method for elevation angle deviation, a comparison is made between the inversion results before and after applying the correction to the elevation angle deviation. The results indicate that the inversion results, after correction for elevation angle deviation, exhibit higher accuracy. The method for correcting elevation angle deviation can effectively rectify the deviation caused by the ionosphere.

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.

We focus on the apparent resistivity method in earthquake precursor observation, develop a detection device suitable for its observation system, and conduct theoretical simulation and on-site testing on the device. First, we analyze the apparent resistivity measurement system, and point out the shortcomings of existing detection systems. Second, according to the demand analysis of observation system, the corresponding detection index and circuit are designed, and the detection accuracy of instrument is designed to 0.001 level to improve the performance. Finally, the developed device is theoretically simulated using Simulink, and the impact of interference on observation results is compared and studied. Random earthquake observation stations in Gansu region are selected for on-site testing. The results show that the developed device can not only visually display the working status of apparent resistivity measurement system, but also accurately evaluate the real-time superiority and inferiority of apparent resistivity observation system, and fill the gap in detection device of apparent resistivity observation system and provide great convenience for frontline earthquake workers.

Current robust fitting algorithms are prone to failure in point cloud data with a high contamination rate. To solve this problem, we introduce a weight matrix in the plane fitting method based on eigenvalue decomposition, where the initial weight is determined based on the normal vector information of point cloud, thus reducing the influence of outliers. We further use the scale-adaptive method to enhance the robustness. The scale factor of this method gradually decreases as the number of iterations increases, effectively solving the problem of low breakdown ration of traditional M estimation. The experimental results show that the breakdown ratio of the proposed algorithm is higher than that of existing robust point cloud fitting methods, and it can accurately estimate plane parameters in the point cloud data with a high outlier ratio.

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 uses the time series of the geocentric motion provided by the Center for Space Research at the University of Texas at Austin as experimental data. First, empirical mode decomposition (EMD) is applied to the data for noise reduction. Then, fast Fourier transform (FFT) and continuous wavelet transform (CWT) are utilized to perform frequency domain transformation, power spectrum analysis, and extraction of periodic terms. Finally, an autoregressive integrated moving average (ARIMA) model and exponential smoothing method are employed to forecast the geocentric motion for the next 20 months. The results indicate that the amplitude and phase of the annual term extracted using FFT are quite close to previous studies on the geocentric motion. The ARIMA model provides better predictions for the Y-direction motion of the geocentric motion over the next 20 months, while exponential smoothing method offers more accurate predictions for the X and Z directions.

Using the BIC_tp noise model identification criterion, we analyzed the temporal noise characteristics of sea surface height (SSH) and their influencing factors at 350 virtual coastal satellite altimetry stations worldwide. Furthermore, we explored the impact of environmental loads on SSH time series and the characteristics of sea level changes across different time spans. The results indicate that the assumptions of FN+WN, FN+RW+WN, and PL+WN noise models can lead to errors in estimating the velocity parameters of SSH time series. Furthermore, there is a diversity of SSH time series noise models, and the velocity uncertainties under different noise models vary significantly. Identifying their noise characteristics is crucial for accurately obtaining sea level change parameters. The average global sea level rise rates for the different time spans of 1993 to 2006, 2007 to 2020, and 1993 to 2020 are 2.59 mm/a, 4.41 mm/a, and 3.08 mm/a, respectively, indicating that sea level is accelerating its rise. The optimal noise models and velocity changes for the SSH time series before and after environmental loading correction are not significant, indicating that the load effect has a relatively minor impact on the characteristics of SSH time series.

We use the ESPAC method to detect the geological structure below the Mogao Grottoes of Dunhuang using observed data obtained by linear array. The detection results show that the layers determined by microtremor survey method are clearly visible, with significant fluctuations of each layer on the two-dimensional microtremor apparent S-wave velocity profile. The covering layer is thick at both ends and thin in the middle. There is a bedrock intrusion in the middle of profile, and there is a solitary stone with a width of 30 m×40 m. Using geological survey data calibration of the relevant region, we show that the thickness of Quaternary cover layer represented by mixed backfill, fine sand, and gravel sand is about 8 m, and the burial depth of complete bedrock surface is about 30 m. The research results can provide geophysical basis for the protection of cultural relics in the Mogao Grottoes.

We use T-shaped, linear, regular pentagonal, and spiral arrays at the same site for micromotion detection comparison experiments to analyze the effects of cross-correlation time window length, geometry of observation array, and their spreading on the quality of frequency-Bessel (F-J) dispersion energy imaging. The results indicate that, for the same observation time, increasing the cross-correlation time window length can effectively distinguish the fundamental and higher-mode dispersion curves, but it will reduce the number of superposition segments, resulting in lower dispersion spectrum resolution.The F-J method does not have special requirements for the arrangement of observation array and is suitable for random and linear distributions. When the array aperture is the same, the quality and resolution of dispersion imaging for an observation array with a greater number of array spacing combinations will be higher. The F-J method has certain requirements for the deployment range of observation array. For example, when the deployment range is too small, the quality of dispersion imaging using the F-J method is poor and it is unable to separate higher-mode dispersion curves.

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.

In response to the problems of premature convergence and easily falling into local optima when using traditional global optimization algorithms such as particle swarm optimization and simulated annealing for dispersion curve inversion, we introduce the bald eagle search (BES) algorithm into the study of dispersion curve inversion. Through inversion analysis of multiple typical geological theoretical models and measured data from the Wyoming region of the United States, the results show that the BES algorithm has strong applicability, stability, and noise resistance in the inversion of Rayleigh wave dispersion curves.

The dynamic evolution characteristics of regional gravity field at different time scales before the Wushi M_S7.1 earthquake are obtained by using the mobile gravity observation data of southern Tianshan area from 2020 to 2023, and the approximate field source depth corresponding to each order wavelet gravity detail is obtained by power spectrum analysis method. The results show that: 1)Before the Wushi M_S7.1 earthquake, the gravity changes in Wuqia-Bachu and Aksu areas show an obvious four-quadrant distribution, and the epicenter is located at the edge of four quadrants and near the zero line. 2)The wavelet transform results of gravity field in southern Tianshan area from 2020 to 2023 show that before the Wushi M_S7.1 earthquake, the gravity changes in Wuqia-Bachu area shows obvious four-quadrant distribution, and the epicenter is located at the edge of four quadrants and near the zero line.

Based on 26 496 BDS monitoring sequences with various observation durations in 2023, we establish quantitative function expressions relating the availability rate, monitoring precision of BDS results to observation duration. The results show that there is a significant positive correlation between the availability rate of monitoring results and observation duration, with an average correlation coefficient of 0.73 for six monitoring stations. The monitoring precision in N, E, U directions exhibit significant negative correlations with observation duration, with correlation coefficients of -0.83, -0.90, and -0.77, respectively. To ensure high timeliness, high availability rate (>95%), and high precision (horizontal precision better than 3 mm, vertical precision better than 5 mm), an optimal observation duration of 3 hours is recommended.

In order to investigate the tectonic characteristics, planar distribution, and active period of the buried fault (Hetan-Guotan buried fault) in the northern margin of Zhongwei basin, Ningxia, we apply the method of shallow seismic exploration to the attitude, character, position and burial depths of uppermost aspects of this buried fault. Furthermore, the composite drilling section explores the exact location and more reliable uppermost point, and we identify the latest active period of this buried fault by a sample dating test. The results show that the Hetan-Guotan buried fault is a normal fault trending near EW and dipping S, extending for approximately 12.5 km. The uppermost point of this fault is buried at a depth of more than 38 m, and the apparent dip of the fault is 75°. The Hetan-Guotan buried fault is not an active fault, because its latest active period was the middle-late middle Pleistocene, and it has been inactive at the end middle Pleistocene and since the late Pleistocene.

We investigate the crustal stress field in Inner Mongolia using 728 focal mechanism solutions and 14 460 P-wave polarity data derived from 2 793 earthquakes based on three different strategies. The Inner Mongolia area is divided into 1°×1° grids, and three methods are applied: a composite focal mechanism solution method based on first-motion polarity data, a Bayesian right trihedra method(BRTM) based on focal mechanisms, and a weighted fusion method of polarity and focal mechanism data. The results from polarity-based and focal mechanism-based methods show good consistency. The abundance of polarity data, compared to limited focal mechanism data, enables stress inversion in a wider spatial extent. After weighted fusion of polarity-based results with focal mechanism data, the BRTM successfully obtains stress results at 125 grid points, expanding the coverage and reducing uncertainties. The study reveals significant spatial variations in the stress field across Inner Mongolia area. The eastern regions are dominated by shear and extension, with shearing concentrated along the Daxinganling and extension characterizing the basins on both sides. Localized compression is observed near Chifeng and Tongliao in the southeast. The northern margin of Ordos block exhibits extension characteristics, while the Alxa block displays shear features. The orientations of maximum principal stress exhibit considerable differences, while the minimum principal stress directions remain relatively uniform.

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.

In traditional techniques, trenching is generally used to reduce the impact of high-speed trains on surrounding buildings. To explore the effectiveness of this method, we use a combination of numerical simulation and on-site experiment to verify the vibration isolation effect of isolation ditches. Based on large-scale finite element software, we compare numerical models with on-site experimental results, and analyze the dispersion characteristics of Rayleigh wave elliptical polarization as high-speed trains pass through viaduct. The results show that when high-speed trains pass through viaduct, a stable surface wave field is formed, which is like the excitation of a single point seismic source. When an isolation ditch is installed on the line, the soil vibration behind isolation ditch shows a certain degree of attenuation, and the isolation effect is obvious.

We combine the latest horizontal and vertical GPS velocity fields in the southeastern margin of Qinghai-Xizang plateau, based on the strain solving method of spherical wavelet multi-scale analysis, consider the weight relationship between regional seismic moment and strain distribution, obtain the three-dimensional crustal strain characteristics of the southeastern margin of Qinghai-Xizang plateau, and analyze the relationship between regional deformation characteristics and seismicity. The results show that: 1) There is a consistency between surface strain and vertical strain in the study area. The high surface strain and low vertical strain are mainly concentrated in the central Qinghai-Xizang plateau and northern Jinshajiang regions, while the low surface strain and high vertical strain are mainly concentrated in the Eastern Himalayan Syntaxis and Longmenshan regions. The spatial inverse distribution relationship between surface strain and vertical strain shows that the horizontal velocity and vertical velocity obtained by GPS observation in this region are coupled, which indicates that vertical motion is also an indispensable consideration for the study of crustal deformation and seismic risk in this region. There is a good agreement between surface strain and vertical strain in terms of magnitude, which further indicates that the crustal deformation in this region can be approximated as a continuous and homogeneous elastic behavior. 2) There is a consistency between the type of strain rate and focal mechanism solution. The strain types obtained from GPS data in the southeastern margin of Qinghai-Xizang plateau can be well matched with the focal mechanism solution in this region. The source mechanism of normal fault is mainly distributed in Jinshajiang region, thrust fault is mainly concentrated in Longmenshan and Eastern Himalayan Syntaxis regions, and strike-slip fault is mainly distributed near the fault zone with significant strike-slip shear such as Xianshuihe-Xiaojiang fault, indicating that the strain characteristics obtained from GPS observation can better describe the tectonic stress field characteristics in this region. Combined with the spatial distribution characteristics of stress and strain in this region and seismic tomography results, we believe that the Longmenshan fault and Eastern Himalayan Syntaxis are in compressive strain state.

The solar pressure perturbation, as the largest non-conservative force experienced by in-orbit navigation satellites, is an important error source for precise orbit determination. Currently, most solar radiation pressure models are established for global positioning system(GPS) satellites, and there is relatively little adaptability analysis of solar radiation pressure models for precise orbit determination accuracy of Beidou-3(BDS-3) satellites. We use observation data from the multi-GNSS experiment(MGEX) to conduct orbit determination experiments based on five solar radiation pressure models, including ECOM1-9, ECOM1-7, ECOM1-5, ECOM2, ECOMC. The results show that the applicability of solar radiation pressure model varies for satellites developed by different manufacturers. For satellites developed by China Academy of Space Technology(CAST), the ECOMC model exhibits optimal applicability in radial, tangential, and normal directions. For satellites developed by Shanghai Engineering Center for Microsatellites(SECM), the radial, tangential, and normal directions have the best accuracy for ECOM1-5, ECOMC, and ECOMC models, respectively. For 3D entirety, the ECOMC model is recommended for orbit determination of both CAST and SECM satellites. From the 24-hour prediction results, for CAST type satellites, the accuracy of ECOM1-9, ECOM1-7, ECOM1-5, ECOM2, and ECOMC models is 23.3 cm, 20.6 cm, 17.2 cm, 21.8 cm, and 10.4 cm, respectively. For SECM type satellites, the accuracy is 25.7 cm, 19.1 cm, 15.9 cm, 12.9 cm, and 11.9 cm, respectively.

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 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.