15 April 2026, Volume 46 Issue 4
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Journal of Geodesy and Geodynamics. 2026, 46(4): 392-398. https://doi.org/10.14075/j.jgg.2025.06.202
Taking a certain medical and chemical industrial park as an example, based on the Sentinel-1 satellite data from 2016 to 2024, we analyze the spatiotemporal characteristics of ground deformation in response to environmental governance using SBAS-InSAR technology. The results show that the study area exhibits spatial characteristics of "overall stability with localized subsidence". The maximum cumulative settlement reached 125 mm, primarily attributed to production activities. The factory zones of large enterprises maintained relative stability, and environmental governance project has not had a significant impact on the safety of enterprise buildings and structures. During the environmental governance period, settlement occurred at both ends of the dam, while the settlement in mid-dam conforms to the consolidation characteristics of the earth-rockfill dam, indicating extraction well operation did not have a significant impact on the stability of the dam. The study area has sufficient water resources and timely groundwater recharge, and reasonable extraction well layout and scientific strategy of the environmental governance plan, which have not caused significant disturbance to the regional hydrogeological environment and has limited impact on ground deformation.
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Journal of Geodesy and Geodynamics. 2026, 46(4): 399-407. https://doi.org/10.14075/j.jgg.2025.05.167
Taking Nujiang prefecture as the research object, a MS7.0 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.
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Journal of Geodesy and Geodynamics. 2026, 46(4): 408-417. https://doi.org/10.14075/j.jgg.2025.04.118
We integrate multi-source heterogeneous data such as time-series InSAR, LiDAR, engineering geological survey, and drilling to systematically analyze the deformation evolution mechanism of Yingzi landslide in Jinyang county, Liangshan Yi autonomous prefecture, and construct a 3D high-resolution dynamic model that enables real-time forecasting of the hazard process. The results show that: 1) InSAR observations (from 31 Dec 2021 to 15 Dec 2024) reveal that the cumulative displacement of landslide reached -198.01 to 150.51 mm, with the most pronounced deformation localized in zone Ⅰ 1(frontal traction section) and zone Ⅰ 2 (ancient landslide zone). 2) The failure mode follows a compound mechanism of frontal traction-rear compression, which can easily drive shear-plane coalescence and trigger overall instability. 3) Scenario-based simulations indicate that the landslide motion-deposition process lasts about 300 s, with a peak velocity of 55 m/s, and forms a deposit covering 2.96×105 m2 with a volume of 5.84×106 m3 and a maximum accumulation thickness of 58.46 m, posing an extremely high risk of river blockage and collapse flooding disaster chain. 4) It is recommended to densify monitoring networks in zones Ⅰ 1 and Ⅰ 2 to capture abrupt deformation, install anti-slide piles and upgrade drainage system at the front edge of zone Ⅰ 1 to inhibit sliding, and initiate relocation of residents in the affected zone. The outcomes provide technical guidance for deformation mechanisms understanding, dynamic modeling, and risk mitigation of high-elevation and long-runout landslides.
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Journal of Geodesy and Geodynamics. 2026, 46(4): 418-423. https://doi.org/10.14075/j.jgg.2025.06.193
We construct daily line-of-sight gravity difference (LGD) series at 5-second intervals using GRACE inter-satellite ranging data and extract LGD anomalies over earthquake regions. Using the 2004 Sumatra MW9.1 and 2011 Tohoku MW9.1 earthquakes as case studies, the results confirm that the LGD method can effectively detect coseismic gravity changes within several days after earthquake, and significantly improve temporal resolution. The observed LGD and theoretical LGD peaks show excellent agreement, with absolute differences no more than 0.8 nm/s2 (Sumatra earthquake) and 2.5 nm/s2 (Tohoku earthquake). This study demonstrates that LGD-based earthquake monitoring offers high speed and accuracy, providing a new technical approach for investigating large-scale mass migration processes caused by seismic events.
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Journal of Geodesy and Geodynamics. 2026, 46(4): 424-434. https://doi.org/10.14075/j.jgg.2025.04.142
Based on GRACE-FO observations from March to April 2022, we analyze the consistency between precise orbit products and KBR/LRI inter-satellite kinematic measurements. The results show that the residuals between KBR/LRI and inter-satellite range, range rate and acceleration derived from the orbit solutions are ±4 mm, ±1×10-5 m/s and ±1×10-5 m/s2, respectively, with RMS values range from 10-6 to 10-3, confirming the reliability of orbit data. In gravity field inversion, the line-of-sight inter-satellite range rate inversion results derived from orbit data exhibit stripe-like noise. The accumulative degree variance of spherical harmonic coefficients is one order of magnitude higher than that of KBR/LRI, and the signal-to-noise ratio is also reduced by about 1. However, in terms of low-degree spherical harmonic coefficients below degree 20, the deviation between this result and CSR reference coefficient is smaller. This phenomenon indicates that orbit data has an advantage in constraining the long-wavelength signals in specific frequency bands for low-degree gravity field model inversion, and can provide valuable supplementary references for multi-source data fusion.
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Journal of Geodesy and Geodynamics. 2026, 46(4): 435-442. https://doi.org/10.14075/j.jgg.2025.03.108
Abstract: Using ascending and descending SAR images from Sentinel-1A satellite, the co-seismic deformation of the MW5.7 earthquake in Zaduo county, Yushu city on March 7, 2024, was obtained. The geometry parameters and slip distribution of the seismogenic fault were inverted. Finally, based on the Coulomb stress changes induced by the earthquake, the impact on surrounding faults was analyzed and the regional seismic hazard was assessed. The results show that the main deformation areas of the co-seismic deformation fields from both ascending and descending orbits exhibit a four-quadrant distribution, with maximum LOS displacements of approximately 3.1 cm and 3.6 cm for ascending and descending orbits, respectively. Fault inversion experiments indicate that both the northeast-dipping fault model and the northwest-dipping fault model can reasonably explain the surface deformation caused by this earthquake. However, after a comprehensive analysis of co-seismic fitting residuals, regional active fault distribution, and geomorphic features, this study leans towards the conclusion that the seismogenic fault of this earthquake is a northeast-dipping strike-slip fault with a northwest-southeast trend. Co-seismic slip is concentrated at depths of 1.5 to 6.0 km, reaching a peak slip of 1.0 m at a depth of 3.7 km. Additionally, the static Coulomb stress changes reveal that the 2024 Zaduo earthquake has increased the risk of future earthquakes in the Yanshiping fault zone.
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Journal of Geodesy and Geodynamics. 2026, 46(4): 443-450. https://doi.org/10.14075/j.jgg.2025.06.194
We collect the focal mechanisms of M≥3.0 earthquakes in western Yunnan region from 2013 to 2024, use the superimposed stress field method to carry out regional tectonic stress inversion, and investigate the spatiotemporal evolution characteristics of focal mechanism consistency before and after M≥5.0 earthquakes. The results show that the focal mechanism in the study area is mainly slip-type, supplemented by normal fault type. The plunge angles of P-axis and T-axis are small, and the fault plane is mostly high dipping. The stress type in the study area is slip-type. The compressive stress is mainly in the direction of NE to NNE, with a better consistency, while the tension stress is dominant in the direction of SEE. The dip angles of compressive stress and tension stress are small and close to the horizontal in western Yunnan. The study area is mainly characterized by horizontal stress and is subject to horizontal compression in the NE to NNE direction and tension in the SEE direction. The M≥5.0 earthquakes occurred in areas with low variance of stress tensor or their edges, and the stress tensor variance experienced the process of decreasing from the peak before the earthquake. The continuous decrease or low level of stress tensor variance may be closely related to the risk of moderate earthquakes in the western Yunnan, but the relationship between them is not unique, and can be comprehensively analyzed by combining with other parameters, such as the low b-value. The research findings provide a reference for analyzing seismic source characteristics, studying tectonic stress, and tracking seismic activity in the study area.
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Journal of Geodesy and Geodynamics. 2026, 46(4): 451-457. https://doi.org/10.14075/j.jgg.2025.05.174
To investigate the seismogenic structure of the 2025 Maduo MS5.5 earthquake in Qinghai province, we use the double-difference relocation method to precisely determine the hypocentral distribution of Maduo earthquake sequence, and calculate the tectonic stress field in the epicentral region. The fault plane parameters are derived using the Gauss-Newton and simulated annealing algorithms. Based on these results, we characterize the kinematic properties of seismogenic fault and compute the coseismic displacement field using an infinite half-space elastic model. The results show that the Maduo earthquake sequence is dominated by a near-horizontal SW-NE-oriented principal compressive stress axis and a NW-SE-oriented principal extensive stress axis, with R-value of 0.42. The fault plane parameters fitted by small earthquakes of Maduo earthquake sequence are strike 43.39° and dip 81.64°, suggesting that the rupture surface is a NE-striking nodal plane, which is a right-lateral strike-slip hidden fault. The coseismic displacement field reveals a maximum horizontal displacement of 12 to 13 mm and a maximum vertical displacement of 3 to 5 mm.
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Journal of Geodesy and Geodynamics. 2026, 46(4): 458-466. https://doi.org/10.14075/j.jgg.2025.04.120
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.
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Journal of Geodesy and Geodynamics. 2026, 46(4): 467-472. https://doi.org/10.14075/j.jgg.2025.05.155
The laser interferometry absolute gravimeter uses the stable frequency laser wavelength as the precise length reference, and the selection of reference source directly affects the accuracy and precision of the measurement results. We focus on the differences in engineering applications between iodine saturated absorption stable frequency lasers and thermally stable frequency lasers. The wavelength accuracy and repeatability of thermally stable frequency lasers are analyzed in detail. We construct a beat frequency measurement system based on iodine stable frequency laser reference, which achieves the measurement of wavelength accuracy and repeatability of thermal stable frequency laser. A statistical processing model with the same final result of absolute gravity measurement is spmpled to quantify the repeatability and accuracy of output wavelength of the tested laser. The results show that the output wavelength accuracy of the tested thermally stable frequency laser is better than 4×10-9 nm, and the repeatability is better than 1.86×10-6 nm. That is, during the locking process of the thermal stable frequency laser, the gravity measurement error caused by wavelength accuracy is much smaller than 1 μGal, and the absolute gravity measurement error caused by wavelength repeatability is 2.79 μGal, which is acceptable for the absolute gravity measurement requirement of 10 μGal observation accuracy. This provides a complete metrological basis for the engineering application of absolute gravity instruments based on thermal stable frequency lasers in field environment.
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Journal of Geodesy and Geodynamics. 2026, 46(4): 473-480. https://doi.org/10.14075/j.jgg.2025.07.250
Aiming at the problems of low accuracy of empirical models and meteorological parameter model accuracy limited by meteorological parameters in commonly used ZTD prediction models, we propose a regional ZTD prediction model based on improved multi-head attention mechanism combined with long short-term memory network (LSTM-MHA). The model is constructed using data from the third-generation global pressure and temperature model (GPT3), along with station latitude, longitude, elevation, day of year, and hour of day. Using ZTD data from 26 continuously operating reference stations (CORS) in Europe in 2023 as reference values, comparative experiments were conducted with the GPT3 model, LSTM model, and CNN model. The results show that the LSTM-MHA model achieves a mean bias close to 0, with root mean square error and mean absolute error of 13.43 mm and 12.4 mm, respectively. The accuracy of LSTM-MHA model has been improved by 60.8%, 55.2%, and 53.3% compared to the GPT3, CNN, and LSTM models. Evaluation of the LSTM-MHA model performance under different distances and prediction lengths reveals that the proposed method performs stably in both sparse station networks and long-term forecasting scenarios, demonstrating its suitability for regional multi-station prediction tasks.
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Journal of Geodesy and Geodynamics. 2026, 46(4): 481-486. https://doi.org/10.14075/j.jgg.2025.04.136
To analyze the differences of different singular integral methods in geoid calculation using Stokes integral, based on the traditional methods using circular approximation and biquadratic polynomial interpolation, we derive a de-singularized method for Stokes integral within the integration radius. The results show that when the innermost area is selected as the single grid where the calculation point is located, the accuracy of traditional method and biquadratic polynomial interpolation method are similar, and the de-singularized method has been improved using the point kernel numerical integration. The mean kernel numerical integration can improve the calculation accuracy of traditional method and biquadratic polynomial interpolation method, while the de-singularized method is not significant.
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Journal of Geodesy and Geodynamics. 2026, 46(4): 487-496. https://doi.org/10.14075/j.jgg.2025.06.201
Based on reduced-dynamic method, we utilize sliding window to achieve near-real time orbit calculation and recursive update for low Earth orbit satellites, and verify the accuracy and effectiveness of orbit determination. Taking the observation data of GRACE-FO and Swarm-B satellites from January 15 to 26, 2025 as an example, the results show that there is no significant systematic error in the tangential, normal, and radial orbit overlapping arc segments calculated using sliding window. Compared with the official released precise science orbit, the root mean square (RMS) of orbit difference in calculation part in three directions is all within 5 cm, and the residual RMS of satellite laser ranging (SLR) validations are 3.03 cm, 4.14 cm, and 3.15 cm, respectively. At a predicted arc length of 60 minutes, the average radial orbit RMS of three satellites is about 10 cm. In addition, changing the initial value of subsequent arc segment orbit from standard point positioning (SPP) to reusing the calculation and extrapolation result of previous arc segment orbit can shorten the single arc segment solution time from 10 minutes to 5 minutes.
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Journal of Geodesy and Geodynamics. 2026, 46(4): 497-502. https://doi.org/10.14075/j.jgg.2025.06.195
We investigate orbit determination and prediction for low Earth orbit (LEO) satellites using high-precision ranging data from a sparse regional network of ground stations. Aiming at applications with limited observational data, three strategies for resolving the atmospheric drag coefficient (CD) are proposed: 1) Unconstrained estimation using the long-arc CD solution as the initial value. 2) Using the long-arc CD solution as the initial value, and the accuracy factor of long-arc CD solution as the accuracy constraint. 3) Directly using the long-arc CD solution as a fixed value. The results show that the mean orbit determination residuals for all three strategies are below 0.17 m. Compared to the precise orbit, the 3D orbit determination accuracy for all three methods is better than 10 m. For the 24-hour predicted arc, the unconstrained solution achieves a RMS better than 55 m, while both the constrained and fully constrained solutions achieve an accuracy better than 15 m. This study verifies the feasibility of independent LEO satellite orbit determination using ground-based high-precision ranging data.
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Journal of Geodesy and Geodynamics. 2026, 46(4): 503-509. https://doi.org/10.14075/j.jgg.2025.06.198
Aiming at the quantitative evaluation of observation environment complexity in GNSS high-precision positioning, a comprehensive subjective and objective weighted combinative distance-based assessment (CODAS) method based on data quality indicators such as data integrity rate, cycle slip ratio, pseudorange multipath error, carrier-to-noise ratio and PDOP is proposed. According to different weighting strategies, the CODAS, TOPSIS and VIKOR methods are used to evaluate the observation environment complexity of 120 monitoring stations, and the Spearman correlation coefficient is used to measure the correlation between evaluation results of each method and the accuracy of PPP kinematics solution. The results show that the comprehensive subjective and objective weighting can improve the accuracy of CODAS method compared with the single weighting. The Spearman correlation coefficients of evaluation results of CODAS method with RMSE and ME are 0.897 and 0.924, respectively, which are better than TOPSIS and VIKOR methods. Parameter sensitivity analysis shows that the mean standard deviation of evaluation results of CODAS method under different trade-off parameters is less than 1.5, indicating good stability.
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Journal of Geodesy and Geodynamics. 2026, 46(4): 510-521. https://doi.org/10.14075/j.jgg.2025.05.175
A "decomposition-reconstruction-prediction" satellite clock offset prediction method based on singular spectrum analysis (SSA) is proposed. This method first decomposes the clock offset time series into trend, periodic, and random signals. Then, based on the significant difference in Hurst exponent among the three types of signals, the reconstructed clock offset signal is determined. Finally, the SSA iterative interpolation algorithm is used to extrapolate the reconstructed clock offset signal and obtain the final predicted clock offset time series. Taking GPS and BDS-3 satellite clock offsets as an example, the results show that SSA can accurately extract trend and periodic signals in clock offset time series. Compared to the quadratic polynomial model with periodic term, grey model and autoregressive integrated moving average model, the proposed method has a smaller root mean square error in prediction and more stable prediction results. For the 12-hour prediction, the average prediction accuracy of GPS satellite clock offset is improved by 38.81%, 59%, and 72.11% compared to the other three models, respectively, while the accuracy of BDS-3 satellite clock offset is improved by 71.54%, 74.82%, and 70.09%, respectively. For the 24-hour prediction, the improvements for GPS satellite clock offset are 51%, 70.66%, and 83.99%, respectively, while the improvements for BDS-3 satellite clock offset are 86.36%, 85.25%, and 81.05%, respectively. It is concluded that the proposed method is effective and practical for satellite clock offset prediction.
