Applying the structural-stratigraphic analysis method, the shallow seismic profile across the fault in southwestern Haizhou depression is interpreted through borehole constraints. On this basis, five important structural interfaces of Yongji subsection of Haizhou section of northern Zhongtiaoshan fault are traced, the activity patterns of fault and sedimentation rates of strata are quantitatively analyzed, and the neotectonic activity episodes in Yongji subsection of Haizhou section of northern Zhongtiaoshan fault are established.

Using Sentinel-1A data, this study employed D-InSAR technology to obtain the line-of-sight (LOS) co-seismic deformation field of the M_S6.8 earthquake in Dingri, Xizang, on January 7, 2025. The geometric parameters of the seismogenic fault were derived through a Bayesian approach. Fault slip distribution was inverted using the SDM, and co-seismic Coulomb stress changes were calculated. The inversion results indicate that the seismogenic fault has a strike of 187.34°, a dip angle of 56.40°, with an epicenter located at 87.50°E and 28.64°N, at a depth of 6.81 km. The maximum slip in the co-seismic slip distribution is 4.24 m, with an average rake angle of-58.82°, suggesting that the earthquake was predominantly a normal faulting event with a minor component of left-lateral strike-slip. The inverted moment magnitude is M_W7.0, and the seismogenic fault is preliminarily identified as the Dengmo Co fault. Additionally, regions along the Zanda-Lhazê-Qiongduojiang fault, Darjeeling-Ngamring-Rinbung fault, and parts of the south xizang detachment system fault, as well as the southern sections of the Xainza-Dingjie fault and Dengmo Co fault, exhibit Coulomb stress increases exceeding 0.1 bar, indicating that these areas warrant greater attention for future seismic hazards.

High-precision polar motion prediction is crucial for applications such as real-time satellite orbit determination and deep space probes navigation. We combine the singular spectrum analysis(SSA) and weighted least squares(WLS) models, which takes into account the temporal variability of periodic components of polar motion. Combining with the auto-regressive(AR) model, we prove the effectiveness of SSA+WLS+AR model in improving the accuracy of polar motion prediction. We analyze the impact of detrending, the length of basic sequence, and the weighting method on the final prediction accuracy of the SSA+WLS+AR model. The results show that in the X direction, the model combination of "no detrending+50-year basic sequence+inverse weighting" has the highest prediction accuracy, while in the Y direction, the model combination of "detrending +50-year basic sequence+inverse weighting" has the highest prediction accuracy. When the prediction span is from 150 to 360 days, the prediction accuracy of SSA+WLS+AR model is better than that of bulletin A provided by international Earth rotation service(IERS), with maximum improvements of 33% and 26% in the X and Y directions, respectively. The prediction results show that the first-day prediction accuracy of polar motion is significantly better using the C04 20 sequence compared to the C04 14 sequence.

To address the low accuracy of zenith tropospheric delay(ZTD) models and the scarcity of water vapor data in Antarctica, we use ZTD data from six global navigation satellite system(GNSS) stations in Antarctica, ECMWF reanalysis v5(ERA5) data, and radiosonde(RS) data from 2018 to 2021. First, the ZTD accuracy of UNB3m, EGNOS, and GPT3 models in Antarctica is analyzed. Then, the ZTD correction and PWV conversion models are constructed separately based on extreme gradient boosting(XGBoost). The results show that the average root mean square errors(RMSEs) of UNB3m-ZTD, EGNOS-ZTD, and GPT3-ZTD of six GNSS stations in Antarctica are 98.12 mm, 116.13 mm, and 24.31 mm, respectively. After correction using XGBoost, the average RMSEs of UNB3m-ZTD, EGNOS-ZTD, and GPT3-ZTD from 2020 to 2021 are 10.46 mm, 10.50 mm, and 10.60 mm, respectively, demonstrating higher accuracy and closeness between the models. The average RMSEs of PWV converted from the corrected UNB3m-ZTD, EGNOS-ZTD, and GPT3-ZTD using XGBoost are 1.71 mm, indicating high accuracy.

To further evaluate the technical performance of domestic independently developed absolute gravimeters, this study conducted comparison observations using multiple absolute gravimeters in the cave of the Huazhong University of Science and Technology National Gravimetry Laboratory. Through unified data processing, high-precision absolute gravity comparison data were obtained. The results demonstrate that no significant deviation exists between atomic interferometry absolute gravimeters and laser interferometry absolute gravimeters in this comparison, with deviations all within -4.95 μGal to 5.31 μGal. Each atomic interferometry absolute gravimeter achieved an observation precision of 1 μGal during continuous 4-hour measurements, with inter-instrument deviations maintained below 10 μGal, demonstrating excellent stability and consistency. This study marks the first comparison measurements conducted on multiple domestically developed absolute gravimeters featuring independent domestic. It involved detailed data processing, scientific evaluation, and a multidimensional performance assessment, providing crucial references for the subsequent development and application of domestic gravimeters.

We quantitatively analyzed the crustal strain changes in Xuzhou and Gaochun areas of Jiangsu province from 2019 to 2023 using four-component borehole strainmeters, and explored the characteristics of regional strain field and its relationship with seismic activity. According to the strain parameter results, both Xuzhou and Gaochun areas were in a stable state during the study period. The response values of tidal factors at Gaochun seismic station exhibited an abnormal change of first dispersion, then stabilization before and after the M5.0 earthquake in Dafeng sea area of Yancheng, Jiangsu province. Through the analysis of its variation characteristics, the relationship with the strike of faults and the focal mechanism solution of earthquakes, it can be inferred that in the process of earthquake preparation, the stress and strain in this area experienced a process from accumulation to release, and the tidal factors can reflect this change to a certain extent.

Based on the structural characteristics of the Xianshuihe fault zone, this study divides the five sections of Luhuo, Daofu, Qianning, Zheduotang, and Kangding-Moxi, and quantitatively reveals the horizontal slip rate and kinematic characteristics of each section through multi-source observation data of cross-fault leveling, baseline/ranging, and horizontal creep. The results show that the whole Xianshuihe fault zone is dominated by left-lateral strike-slip mode from 1982 to 2024. The strike-slip rates of Juwo and Xialatuo in Luhuo section are -0.9 mm/a and -2.86 mm/a, and the cumulative strike-slip displacements are 40 mm and 130 mm, which are significantly higher than the activity intensity of Gelu and Xuxu stations. The strike-slip rates of Goupu and Goupu creep stations in Daofu-Qianning section are -0.97 mm/a and -0.58 mm/a, and the cumulative displacement shows a linear growth trend. The horizontal displacement of Longdengba and Laoganning stations is small, and the local fault zone is weakly sinistral. The Zheduotang observation site in the Kangding-Moxi section shows a +0.2 mm/a dextral strike-slip, while the Yulin observation site maintains a stable left-lateral strike-slip of -0.12 mm/a, and its deformation has significant seasonal fluctuations (amplitude of about 1.5 mm to 2.3 mm). The cross-fault leveling of the Anshun site shows continuous tensile normal fault activity, and the linearity of the movement trend reaches 0.933 and 0.824, respectively.The results of segmented comparison show that the activity intensity of the northwestern section is significantly higher than that of the southeastern section, and the vertical movement shows that the thrust of the northern section and the normal fault activity of the southern section are structural inversion. The segmentation difference is related to the fault geometry and the physical properties of the medium. The medium strength of the conversion layer in the northwest section may be lower than that in the southeast section, which is easy to trigger slip and lead to shorter earthquake recurrence period. Combined with the regional stress field, it is found that the locking degree of the Xianshuihe fault zone has changed in different periods, showing that the fault in the northwest section is more active than that in the southeast section, and the locking is weak. At the same time, after the Wenchuan M_S8.0 earthquake, the Lushan M_S7.0 earthquake, and the Luding M_S6.9 earthquake, the extrusion rate of the Bayan Har block to the Sichuan basin accelerated, which affected the far-field left-lateral strike-slip rate of the Xianshuihe fault and the accumulation rate of fault slip deficit, which in turn led to the difference in the stress and strain accumulation rate of each segment on the Xianshuihe fault zone.

This paper reviews and summarizes traditional estimation methods, highlighting their reliance solelyon observed seismic activity data. If the return period of the maximum earthquake exceeds the data coverage period or seismic activity rates fluctuate over longer timescales, these methods become ineffective. Furthermore, in the absence of physical constraints, traditional approaches may predict unbounded growth in the maximum event magnitude as the temporal scope expands.To address these limitations, this study introduces a new model based on seismic moment conservation. This model integrates instrumental records, fault slip rates, fault geometry, and seismic activity patterns, assuming that seismicity follows the Gutenberg-Richter(G-R) law. By simulating missing large earthquakes and their aftershocks, it constructs a long-term seismic catalog and imposes physical constraints on the maximum magnitude using the seismic moment accumulation rate, effectively mitigating the reliance of traditional methods on observational periods.The model is applied to predict the M_max and return period of the Aerjin fault zone, the Kunlun fault zone, and the Longmenshan fault zone. The results show high consistency with historical earthquake records, paleoearthquake data, and observed slip rates, validating the model's efficacy. This research offers a new perspective on maximum magnitude estimation and provides a valuable tool for seismic hazard assessment in regions with incomplete historical records.

We conduct a detailed analysis of the spatial configuration of Beidou-3 constellation, and construct a dynamic link constraint model from two aspects: satellite visibility and antenna directivity. We obtain the real satellite orbit parameters through two line elements (TLE) file, construct the Beidou-3 constellation based on STK, and comprehensively analyze the topology characteristics of Beidou inter-satellite link. The simulation results have important guiding significance for further completing the link budget, achieving autonomous orbit determination and time synchronization between satellites.

Existing research on GNSS signal classification primarily targets professional-grade receivers, distinguishing between line-of-sight(LOS) and non-line-of-sight(NLOS) signals through the extraction of signal features to achieve high-accuracy positioning. However, the signal features and classification methods used in these studies may not be applicable to the signal characteristics of low-cost GNSS chips in smartphones. This paper proposes a machine learning-based method for classifying smartphone GNSS reception signals into LOS and NLOS. The method combines five key indicators: carrier-to-noise ratio, elevation angle, pseudorange residuals, normalized pseudorange residuals, and pseudorange residual percentage. It also integrates deep learning-based zenith view semantic segmentation and satellite calibration techniques to construct an accurate training dataset. Evaluations of various machine learning models in typical urban scenarios show that the proposed method achieves an average classification accuracy of 85.8% across different smartphone models.

The BDS-3 and Galileo both provide five-frequency signal services. To fully utilize the multi-frequency signal data, a BDS-3/Galileo multi-frequency single point positioning (SPP) model based on the ionosphere-free combination is established, and the multi-frequency ionosphere-free combination coefficients are determined. Data from 48 multi-GNSS experiment (MGEX) stations are selected to systematically evaluate the performance of multi-frequency pseudorange SPP based on the ionosphere-free combination. The experimental results show that multi-frequency combined observations help to improve the SPP positioning accuracy of the BDS-3, Galileo, and BDS-3/Galileo systems. Compared with three-frequency SPP positioning, the positioning accuracy of four-frequency and five-frequency SPP has been improved to varying degrees. The improvement is most significant for the BDS-3 system. For the BDS-3 three-frequency SPP positioning, the RMS mean values in the E, N, U directions are 0.56 m, 0.59 m, 1.46 m, respectively, while the RMS mean values for four-frequency and five-frequency positioning are similar, at 0.53 m, 0.55 m, 1.40 m and 0.52 m, 0.55 m, 1.38 m, respectively. Compared with the single BDS-3 and Galileo systems, the five-frequency SPP positioning accuracy of the BDS-3/Galileo combined system has increased by 30.8%, 29.1%, 25.4% and 28.0%, 30.4%, 25.9%, respectively.

Utilizing continuous observation data from 41 strong-motion stations and 20 China Mobile Beidou CORS stations near the epicenter of the M6.8 Dingri, Xizang earthquake on January 7, 2025, this study systematically evaluates seismic intensity distribution and co-seismic surface deformation characteristics. Results indicate that the maximum instrumental intensity reached 8.0 degree, with significant spatial attenuation (1.67 degrees per 100 km) and anisotropy (isoseismal major axis trending nearly N-S). High-precision co-seismic deformation fields near the epicenter were accurately obtained through Beidou static undifferenced PPP and double-difference baseline network solutions, combined with a dual-epoch median displacement differencing method. Discrepancies with GPS observations were at millimeter level. The Beidou high-dynamic PPP mode effectively captured centimeter-level transient deformation signals. Furthermore, spatial patterns of co-seismic displacement fields from Beidou observations align with theoretical rupture model simulations, consistently demonstrating horizontal expansion west and east of the epicentral area and convergence toward the epicenter from the northern sector.

The variational mode decomposition(VMD) exhibits superior performance, and the setting of K and alpha parameters significantly influences its decomposition result. We optimize the selection of these two parameters based on sparse index, enabling the adaptive determination of the optimal K and alpha values. On this basic, VMD method is applied to seismic signal data observed by four types of second-sampling instruments at Yichang station, including BBVS-60 seismometers, DZW gravimeters, VP-type tiltmeters, and water level gauges, and time-frequency analysis is conducted combining with Hilbert transform. The results show that the optimal K and alpha values differ for each of four instruments. The K value represents the type of coseismic signal frequencies that can be decomposed, suggesting that the four instruments respond differently to the same seismic signal.

To simulate the impact of terrain on co-seismic deformation, this paper established three different terrain models. The results show that compared with flat terrain, convex terrain reduces the amount of horizontal displacement, while concave terrain significantly increases the amount of horizontal displacement. The terrain difference in the epicentral area of the 2024 Wushi, Xinjiang M_W7.0 earthquake is significant, and the impact of the real terrain on the co-seismic deformation of this earthquake is not yet clear. This paper uses the spectral element method to simulate the co-seismic deformation of the Wushi earthquake and compares it with the co-seismic displacement field of D-InSAR. The results indicate that the impact of terrain factors on co-seismic deformation can reach 8.5%, 26.9%, and 6.8% in the E, N, and U directions, respectively.

Based on the observational data of two types of borehole strainmeters at Xuzhou seismic station, we use the R-value test method to calculate and score the forecasting efficiency of trend-breakinganomalies, annual breaking anomalies and rate anomalies recorded by the two instruments. A systematic comparative analysis of the forecasting efficiency of the two borehole strain instruments at the same site is conducted to clarify their complementarity in earthquake precursor monitoring. The results show that the borehole body strainmeter performs well in the forecasting of trend-breaking anomalies and annual breaking anomalies, and is suitable for capturing the earthquake precursor anomaly signals related to long-term geological tectonic activities. The borehole component strainmeter shows a strong ability in the forecasting of trend-breaking anomalies and rate anomalies, and is more adept at capturing the trend-breaking precursor anomaly signals caused by stress state changes of geological body, and has high sensitivity for the monitoring of rapid changes in regional stress and strain. These findings reveal the efficiency differences of borehole strainmeters in earthquake precursor monitoring and provide the application focus and optimization direction of the two types of borehole strainmeters in earthquake forecasting.

Based on the statistical analysis, correlation fitting and preprocessing of high-precision continuous observation data of four trace hydrogen observation points in fault zones of northwestern Yunnan over the past five years, we evaluate the seismic prediction efficiency of observational data, and analyze the characteristics and causes of trace hydrogen concentration anomalies related to earthquakes combining with previous studies. The results show that: 1) The concentration variations of hydrogen escaping from hot springs in northwestern Yunnan are correlated with temperature and air pressure, showing distinct annual variation features. In contrast, hydrogen escaping from soil is essentially uncorrelated with meteorological elements. Comparison with previous studies, there is a significant spatial heterogeneity in the distribution of trace hydrogen concentration in fault zones, which is not controlled by a single factor. 2) All of four trace hydrogen observation points in northwestern Yunnan are effective seismic prediction indicators with statistical significance. The short-term prediction effect of hydrogen escaping from soil is better but with relatively lower credibility. The prediction efficiency of hydrogen escaping from hot springs is mainly in medium to long term, with relatively higher credibility. 3) There is a close correlation between hydrogen anomalies in fault zones and seismic activities in northwestern Yunnan. Seismic precursory anomalies typically manifest as sudden increases or sawtooth fluctuations. Due to differences in hydrogen sources, escaping processes, and geothermal storage temperatures in different regions, the geochemical background values of hydrogen escaping from hot springs and soil also exhibit significant spatial heterogeneity.

Traditional satellite orbit determination methods primarily rely on post-processing on the ground, which results in significant time delays and fails to meet the real-time requirements of autonomous on-board tasks. To address this issue, this paper proposes an autonomous real-time orbit determination algorithm based on the extended Kalman filter (EKF). The algorithm integrates quality control of observational data, dynamic orbit integration, and parameter estimation techniques to achieve real-time orbit determination for low-Earth orbit (LEO) satellites. The accuracy of the algorithm was assessed by comparing the real-time and predicted orbits with the ground-based post-processed precise reference orbits. Results show that, after accumulating 72 hours of observational data, the three-dimensional position error of real-time orbit determination was 15.18 cm, and the three-dimensional position error of orbit prediction within 2 hours was better than 18.75 cm, meeting the requirements for autonomous mission planning. Moreover, validated on an embedded platform, the algorithm has a single calculation cycle of less than 35 seconds and a memory footprint of less than 4 MB, complying with the onboard resource requirements. This study not only provides a theoretical and technical foundation for the design of autonomous navigation systems for medium and high Earth orbit satellites but also holds engineering value for enhancing the real-time response capabilities of satellites in orbit.

At present, the common detection method of integrated navigation system soft faults is to combine the sequential probability ratio test (SPRT) algorithm with the residual Chi-square detection algorithm. However, this algorithm has the defects of low detection accuracy and inability to detect multiple consecutive soft faults. Aiming at this problem, this paper first proposes an improved SPRT detection algorithm based on fading factor to reduce the influence of historical information on fault detection statistics and enhance the effect of current information on fault detection statistics. Then, the fault check statistic of the improved SPRT detection algorithm is designed, and combined with the residual Chi-square detection algorithm, an integrated navigation soft fault detection algorithm is proposed. Finally, based on GNSS/SINS integrated navigation system, this article has carried on the integrated navigation system soft failure detection simulation experiment.The experimental results show that compared with the classical algorithm, residual Chi-square detection algorithm, the improved algorithm not only has high precision and can accurately detect multiple consecutive soft faults, which can guarantee the stability of the integrated navigation system.

Based on the GNSS earth observation network system (GEONET) in Japan and the Taiwan geophysical network for seismology (TGNS) in China, this paper investigates the propagation characteristics of co-seismic ionospheric disturbance(CsIDs) triggered by the 1 January 2024 Noto Peninsula M_W7.5 earthquake in Japan and the 2 April 2024 Hualien M_W7.4 earthquake in Taiwan, China. Meanwhile, the reasons for the anisotropy of the CsIDs produced by the two earthquakes are discussed. The results show that: 1) For the Noto Peninsula earthquake, the seismically excited acoustic waves propagated to the height of the F2 layer of the ionosphere within 8 to 9 minutes, and the triggered CsIDs propagated to the southeast of the epicenter at a speed of ~0.89 km/s, with a maximum amplitude of 0.768 TECu. The 2-minute rate of TEC index (ROTI) maps show higher sensitivity than the 2D-filtered TEC maps. 2) The CsIDs of the Hualien earthquake were also excited by acoustic waves and reached the height of the F2 layer of the ionosphere after ~8 minutes, with a maximum amplitude close to 0.4 TECu. 3) The propagation direction of the CsIDs triggered by the Noto Peninsula earthquake was strongly linked to the geomagnetic field, whereas those triggered by the Hualien earthquake were influenced by both the source mechanism and the geomagnetic field.

We investigate the deviation between IGRF13 model data and unmanned aerial vehicle(UAV) geomagnetic data in localized regions of China. By analyzing the differences in total geomagnetic field intensity, as well as the northward, eastward, vertical, and horizontal components of geomagnetic field between IGRF13 model data and aeromagnetic data in Weishui in Shaanxi province and Yuyao in Zhejiang province. The results show that the difference in total geomagnetic field intensity between IGRF13 model data and geomagnetic data in localized regions of China ranges from 100 to 200 nT. In the northwestern region of China, the difference is approximately 100 nT, while in the eastern coastal region, it is around 200 nT. After systematic calibration, the mean absolute error between the two datasets is less than 50 nT.

A combined positioning method that integrates ultra wide band (UWB) with low-cost micro-electro-mechanical systems (MEMS) inertial measurement unit (IMU) is proposed. Initially, UWB ranging data is optimized using ranging bias correction and Kalman filtering. Subsequently, the complementary strengths of multiple sensors are leveraged through a UWB/IMU fusion model. Experimental results demonstrate that the optimized UWB achieves an improvement in average positioning accuracy from 15.70 cm to 13.75 cm, with the RMSE decreasing from 22.45 cm to 19.70 cm. In non-line-of-sight (NLOS) scenarios, even when UWB signals experience abrupt changes or are lost, the fused system can still provide continuous and reliable positional information, with an average accuracy of 13.23 cm and an RMSE of 17.90 cm.

In response to the issue that existing cycle slip detection methods lack systematic performance evaluation tools, this paper proposes a comprehensive evaluation approach that considers all epochs. By uniformly introducing cycle slips across all epochs, the method comprehensively reflects the true performance of different cycle slip detection algorithms over the entire observation period. Starting from three dimensions: combined noise, test statistic detection performance, and cycle slip detection results, three performance indicators are constructed: the root mean square error (RMSE) of the test statistic, the ratio of test statistic variation to RMSE, and the missed detection probability over all epochs. These indicators are used to systematically evaluate the performance differences of five cycle slip detection algorithms: Melbourne-Wübbena (MW), sliding window improved MW, triple-frequency pseudorange and phase, triple-frequency geometry-free (GF), and triple-frequency second-order time-difference phase ionospheric residual (STPIR). The results show that for all cycle slips within two weeks of the B1C/B2a/B3I signals, the triple-frequency GF cycle slip detection algorithm with a combination coefficient of (1, 2, -3) performs the best. Its test statistic RMSE is 0.006 2, the ratio of test statistic variation to RMSE is 100.56, and the missed detection probability over all epochs is only 7.28%. This performance evaluation method provides an objective quantitative basis for comparing the performance of cycle slip detection algorithms.

We quantify surface water storage anomalies using GRACE satellite Mascon data and hydrological model data combining with water level and area data, estimate groundwater storage anomalies in Dongting Lake basin based on water balance equation, analyze the spatiotemporal variation characteristics and influencing factors of groundwater storage anomalies. The results show that after incorporating changes in surface water storage, the correlation between the inverted groundwater storage anomalies at the lake scale and the observed groundwater data improved from 0.40 to 0.65, reaching 0.75 in areas with dense groundwater wells. The overall groundwater storage anomalies in Dongting Lake basin show a downward trend, with a loss rate of-5.05 mm/a. Spatially, there is a significant difference between the northern and southern areas. Precipitation influences groundwater storage anomalies through its impact on surface water, with some lag due to hydrological processes, while human activities have a limited effect. This study reduces uncertainties generated in separating surface water storage, providing data support for groundwater dynamic research and water resource management in Dongting Lake basin.

To address the issue of deviations in amplitude extraction caused by unmodeled errors in global navigation satellite system interferometric reflectometry(GNSS-IR) soil moisture inversion, this study proposes a method that utilizes a semi-parametric model to introduce nonparametric vectors compensating for unmodeled errors, thereby optimizing amplitude extraction. The soil moisture inversion results based on parametric models are compared with those derived from semi-parametric models. The findings demonstrate that the amplitude extracted by the semi-parametric model achieves higher accuracy in both single satellite and multi-satellite fusion scenarios. The proposed approach effectively improves inversion precision by mitigating unmodeled errors through semi-parametric compensation.

Using the real-time orbit and clock products from CNES over a one-year period, with URE(user range error) as the evaluation metric, this study analyzes the fault rates, fault types, fault sources, as well as the post-fault accuracy and precise point positioning(PPP) performance of GPS, Galileo, BDS-2, and BDS-3 by comparing them with post-processed products. The results indicate that the fault rates of GPS and Galileo are lower than those of BDS, with significant differences observed between the fault rates of BDS-3 and BDS-2. Regarding fault types, abrupt faults are the least common, while clock offsets are the primary source of faults(accounting for over 65%). After fault elimination, the mean URA(user range accuracy) values for GPS, Galileo, and BDS-3 are 0.02 m, 0.03 m, and 0.05 m, respectively, whereas there is considerable variation in URA among different satellites in BDS-2. Global station simulated kinematic PPP tests demonstrate that excluding satellite fault periods can effectively ensure positioning accuracy.

Based on ground-based single-antenna GNSS receivers, the global navigation satellite system-interferometric reflectometry(GNSS-IR) technique can utilize the signal-to-noise ratio(SNR) to invert the vertical distance between the reflective surface and the antenna, thereby estimating water level heights. To reduce equipment costs and enhance the accessibility of GNSS-IR technology, while fully leveraging existing deformation monitoring GNSS stations, this study proposes the use of universal BDS/GNSS receivers for monitoring the structural deformation of large bridges. By integrating quality control, error correction models, and result fusion methods, effective monitoring of water level changes beneath bridges is achieved. Processing data from two universal BDS/GNSS receivers installed on the main cable of the Guojiatuo Changjiang bridge in Chongqing, which are used for monitoring bridge structural deformation, the study results indicate that the GNSS-IR water level time series, after quality control, error correction, and fusion processing, are highly consistent with the data trends from traditional hydrological stations, with a correlation coefficient reaching 0.99. This outcome not only validates the feasibility of this method in monitoring water level changes beneath large bridges but also demonstrates the broad application prospects of universal BDS/GNSS receivers in river water level monitoring, providing robust data support for flood early warning and water resource assessment.

Using GNSS observation data of Chinese mainland from 1996 to 2016, we invert the current slip rates of active faults around Longxi block based on elastic block model. Combined with the historical earthquake catalog, we calculate the seismic moment deficit of each fault and analyze the spatial distribution of seismic b-value in Longxi block and its surrounding regions to assess seismic risk. The results show that the Haiyuan fault zone exhibits high-rate left-lateral strike-slip motion with a compression component, while the Liupanshan fault zone is dominated by crustal shortening and compression with a strike-slip component in both its northern and southern segments. The northern margin of western Qinling fault zone is primarily characterized by left-lateral strike-slip motion, with an extensional component in its western segment and a compression component in its eastern segment. In terms of seismic risk, significant seismic moment deficits have accumulated in the arcuate tectonic region where the Hasishan-Machangshan segment of Haiyuan fault zone meets the northern segment of Liupanshan fault zone. Meanwhile, the Jinqianghe, Maomaoshan, and Laohushan faults within the Tianzhu seismic gap show rapid stress accumulation and high seismic moment deficits. The Maxianshan fault zone exhibits high compression slip rate and a low b-value, indicating high stress accumulation. Additionally, the Zhuanglanghe fault zone has a substantial seismic moment deficit. These fault zones all possess the potential to generate moderate-to-strong earthquakes.

We utilize long-term observation data from five superconductor gravimeters in China and Europe within the IGETS network, and apply various atmospheric pressure correction strategies to analyze the impact of time-varying admittance on the determination of Earth tide parameters. The results show that the temporal variability of admittance significantly influences Earth tide parameters, with effects on time-varying characteristics of the Earth's free core nutation period reaching up to 10 sidereal days. Taking into account the time-varying characteristics of admittance and global atmospheric pressure effects correction, the tidal wave amplitude factor is found to be closer to theoretical values. This has important implications for the construction of regional tidal models and subtle dynamic signals analysis.

In order to improve the accuracy of ZTD model, a fine-scale stratification ZTD (ZTDFS) model in China is proposed. The new model is finely stratified below 10 km and takes into account the seasonal and daily variation characteristics of each layer. At the same time, the model also fully considers the spatiotemporal variation of the vertical lapse rate of third-order exponential function. The radiosonde data shows that the mean RMSE of ZTDFS model is 31.43 mm, which is 36.6% smaller than that of GPT3 model. The GNSS ZTD data shows that above 500 m, the mean RMSE of ZTDFS model is 28.64 mm, which is improved by 9% compared to GPT3. With the increase in altitude, the performance advantage of ZTDFS model gradually emerges.

We analyze the geochemical characteristics of five hot spring fluids in Eryuan and its surrounding areas, and explore the relationship among geothermal distribution, mantle-derived fluid degassing, hydrochemical anomalies, and seismic activity. The results show that hydrochemical type of hot springs in the study area include HCO₃·SO₄-Na·Ca, HCO₃·SO₄-Na, HCO₃·Cl-Na, SO₄-Ca·Na, and SO₄·Cl-Na·Ca. The main sources of hot spring gases are atmospheric saturated water and air, with contributions from volatile components in the crust and mantle. The heat storage temperatures of hot springs in the study area ranges from 164 to 275 ℃, and circulation depths is from 6 369.78 to 11 143.98 meters. The content of He is from 12.90 to 821.62 ppm. Large-scale deep faults in Eryuan area provide favorable channels for the upward migration of deep-sourced fluids, and the deep-sourced fluids are the direct sources of geothermal energy and He. There is a correlation between the geochemical characteristics of hot spring fluids and seismic activities, which is characterized by the deeper the circulation depth, the higher the geothermal reservoir temperature, and the stronger the seismic activity. Moreover, most of the M≥4 earthquakes are located in the transition zone between high and low geothermal reservoir temperatures. The Cl^- and SO₄^2- concentrations of Wenmiao hot spring show abnormal increases before and after earthquakes, mainly due to the contribution of the mixing of deep-sourced fluids and different aquifers. The temperature at spring outlet shows an abnormal decrease, which may be related to the fact that multiple fractures provide heat dissipation channels after the earthquake. The hydrochemical values of hot springs were restored after the earthquake, indicating that the deep-sourced fluid activity in Eryuan area weakened.

Existing landslide research is mostly limited to single deformation data, ignoring the influence of multidimensional environmental characteristics factors on landslide deformation, such as temperature, dew point temperature, precipitation, and spatiotemporal correlation. To address this issue, we propose a multivariate Transformer prediction model based on time series InSAR technology. The model integrates multidimensional environmental features and spatiotemporal correlation data, and uses wavelet transform to decompose deformation sequences into periodic and trend components. Different Transformer structures are constructed to predict each component. The results show that the prediction accuracy of this model is significantly better than that of traditional methods, with RMSE of 0.72 mm and R² of 0.96. This research provides a new approach for landslide deformation prediction and is of great significance for improving early warning capabilities.

Using Schuster statistical test method, the correlation between tidal body stress and moderate and small earthquakes occurred in the epicenter and its vicinity before the Xizang Dingri M_S6.8 earthquake on January 7, 2025 is investigated. The test results were evaluated by the statistical parameter P value, and the lower the P value, the stronger the statistical significance of the correlation. According to the phase angle statistics of the tidal force modulation caused by the semidiurnal tide and the semilunar tide in the epicenter, the P value of the semidiurnal tide test result is 1.26%, which is lower than triggering threshold of the tidal stress, and most earthquakes occur near the minimum of the semidiurnal tide; the P value of the semilunar tide does not pass the significance test. Further analysis of the temporal and spatial smoothing windows of the P-value based on the semidiurnal tide shows that the P-value decreases significantly before the Dingri M_S6.8 earthquake, and the low P-value area of the spatial smoothing window is concentrated in the north of the epicenter of the Dingri M_S6.8 earthquake. It is shown that the occurrence of moderate and small earthquakes in the epicenter and its vicinity before the Dingri M_S6.8 earthquake is obviously related to the triggering of solid tide, and these moderate and small earthquakes have certain precursory significance for the occurrence of the Dingri M_S6.8 earthquake.

The reliability of SWOT satellite altimetry-based water level data was validated through extraction and analysis, with the July 2024 flood event in the Dongting lake basin serving as a case study to explore its application potential in dynamic flood monitoring. The results demonstrate that the water level data provided by the SWOT satellite exhibits high accuracy, with an optimal correlation coefficient of 0.99 and a RMSE of 0.55 m when compared to in-situ measurements. The derived water extents also show high spatial consistency with optical imagery.

Conventional SBAS-InSAR methods are limited by their inability to capture the full dimensionality of deformation, making it difficult to effectively represent three-dimensional (3D) surface displacements in mining areas. To address this issue, this study proposes a 3D deformation inversion method that integrates ascending and descending SAR data by combining SBAS-InSAR with Offset-Tracking techniques. Using the Liuhuanggou coal mine as a case study, experiments were conducted to derive the 3D surface deformation field. The inversion results were systematically analyzed in terms of subsidence magnitude, affected area, and spatial distribution. Furthermore, leveling data were employed to compare the accuracy of the proposed 3D deformation inversion method with conventional ascending and descending SBAS-InSAR 2D deformation results. This comparison aimed to evaluate the advantages of the 3D decomposition approach over existing 2D methods. The findings indicate that the 3D inversion method aligns more closely with actual leveling data and achieves higher inversion accuracy than the 2D approach. The proposed method enhances the monitoring precision of SBAS-InSAR to a certain extent and expands its measurement dimensionality, thereby providing a novel and effective technical reference for surface deformation monitoring in mining areas.

By comparing the differences between various drift models and adjustment methods through simulated gravity data adjustment, certain optimizations were made to the gravity adjustment algorithm. Methods for multiple segment difference adjustment and constrained linear programming adjustment were proposed. The results indicate that the multiple segment adjustment method outperforms other adjustment methods in some aspects, while the constrained linear programming adjustment method demonstrates overall superiority over other adjustment methods.

We analyzed the Dingri M_S6.8 earthquake as a case study. A multivariate dataset comprising land surface temperature, net surface solar radiation, and other variables in the study area was constructed. After decomposing the time series of each variable, the generalized extreme studentized deviate(GESD) algorithm was applied to extract anomaly signals. The weighted averaging method was then employed to integrate multi-variable anomaly extraction results. The results indicate that the thermal infrared anomalies in the half-year period before the Dingri M_S6.8 earthquake exhibited a cyclic change pattern of "emergence-enhancement-weakening". The Dingri M_S6.8 earthquake occurred 100 days after the maximum value of the anomalies appeared, and the main direction of the anomalies was NW-SE, forming an approximately 45° angle with the Dengmo Co fault, which is the seismogenic structure of this earthquake.

A two-dimensional strain tensor model is established to analyze the spatio-temporal deformation characteristics of a landslide. The results indicate that the landslide deformation exhibits spatio-temporal heterogeneity. During the initial monitoring stage, the front edge of landslide was dominated by compressive deformation, while the middle and rear edges showed a combination of expansion and shear deformation, with intensity rapidly decreasing over time. After the reinforcement of retaining wall, a brief period of strong compressive deformation occurred at the front edge of landslide, with a maximum compressive strain rate of -6 μstrain. In April 2021, a localized landslide occurred at the rear edge of landslide, characterized by strong localized tensile and shear deformation, with a maximum shear strain rate of 150 μstrain and a surface expansion strain peak of 30.9 μstrain. After the sliding event, only the surface expansion intensity diminished rapidly. Moreover, strain extremes along the crack between PB03 and PB04 persisted over time, showing a polarity reversal six months before the landslide, revealing potential risks even during the macroscopically stable deformation stage.

Taking Nujiang prefecture as the research object, a M_S7.0 earthquake was set in the southern section of Nujiang fault. Based on the Newmark model and using basic data such as DEM and geological maps, the Arias intensity seismic motion parameter was selected, and the amplification effect of topography on seismic motion was considered to conduct a potential landslide hazard assessment in Nujiang prefecture, obtaining the spatial distribution pattern of potential seismic landslides in the study area. The results show that the areas with high sensitivity to potential seismic landslides in Nujiang prefecture are mainly distributed along the steep slopes on both sides of the Dulong river, Nujiang river, and Lancang river. The areas with low sensitivity are located in the gently undulating intermountain basins. The probability range of landslide instability is 0-11.69%. In the seismic landslide hazard zoning, the areas of extremely low hazard zone, low hazard zone, moderate hazard zone, and high hazard zone account for 78.11%, 12.23%, 5.69%, and 3.39% of the study area, respectively. The moderate and high hazard zones are mainly distributed in the steep slope areas on both sides of the Nujiang fault. In the study area, 23 natural villages and several highways as disaster-bearing bodies are located in the high hazard zone. This research can provide effective reference for seismic landslide emergency assessment, potential seismic landslide hazard prediction, and site selection for engineering construction in Nujiang prefecture.

Based on the seismic monitoring data from the Ganzhou Earthquake Monitoring Center Station of the Jiangxi Seismological Agency, real-time monitoring of blasting vibrations from different locations and explosive quantities at the Ganzhou Tieshanlong Tungsten Mine was conducted from multiple directions and long distances. The microseismic signals generated by blasting were obtained and analyzed to identify the propagation patterns of blasting vibration signals in medium and far blasting zones. Considering the influence of complex environmental conditions on blasting vibration signals, a Butterworth filter was used to eliminate trend components, and a combination of wavelet denoising and HHT denoising was applied to analyze the time-frequency characteristics, frequency band energy characteristics, and the impact of terrestrial environment on the spectral energy propagation of microseismic signals under different monitoring base stations and different blasting events. The study shows that the Sadovsky empirical formula is still applicable to the propagation patterns of blasting vibration signals in the medium and far blasting zones (32-120 km), where: 1) in the medium and far blasting zones, signal energy is highly concentrated in the low-frequency band and shifts downward with increasing distance from the blast center (R); 2) when the distance from the blast center is fixed, signal energy increases significantly with the increase in explosive quantity (Q), and the concentrated frequency band fluctuates within a normal range; 3) the attenuation of blasting vibration signals is also affected by the surface environment along the propagation path.

We use the joint tomography of first-arrival and reflected waves based on the adjoint techniques and conventional optimization methods to compare the combination methods of three commonly used optimization methods (CG, CGDESCENT, L-BFGS) and line search methods (LNS and CWI), and test the six combination algorithms using anomaly body model and chessboard model. The results show that: 1) For high-speed mutation models, CGDESCENT+LNS has slightly higher accuracy than L-BFGS+CWI, but CGDESCENT did not converge in low-speed models, while both L-BFGS+LNS and L-BFGS+CWI perform well. CGDESCENT is more suitable for large-scale models. 2) Under the same conditions, the accuracy of CWI is slightly higher than that of LNS, but CWI is prone to local minimum and is very unstable.