15 May 2025, Volume 45 Issue 5
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Journal of Geodesy and Geodynamics. 2025, 45(5): 441-446, 476. https://doi.org/10.14075/j.jgg.2024.07.311
Taking the southern section of the Jiayuguan fault as the research subject, the morphology of the hidden segment of the fault was determined through shallow artificial seismic exploration. Based on remote sensing image interpretation and field geological surveys, the fault was found to be exposed at the surface at the southern end of the Jiayuguan fault, forming an anticline fault scarp. Through aerial photogrammetry, combined with dating tests, it was determined that the fault has been active since the late Pleistocene. Using high-precision topographic data, the height of the fault scarp was obtained, and combined with the corresponding geomorphological age, the vertical slip rate of the southern section of the Jiayuguan fault was estimated to be 0.03±0.01 mm/a.
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Journal of Geodesy and Geodynamics. 2025, 45(5): 447-455. https://doi.org/10.14075/j.jgg.2024.06.268
By conducting a comprehensive analysis of two shallow seismic profiles, VSP-measured P-wave velocity data, and one drilling joint geological profile from the Shenqiu depression in the southern north China basin, this study investigates the geometric characteristics and discernible upper fault depths of a series of negative flower-like structures in the shallow part of the strike-slip fault zone. The results indicate that the fault displaces the Quaternary strata upwards, with the discernible upper fault depth on the shallow seismic exploration profile being approximately 60 meters, and the discernible upper fault depth on the drilling joint geological profile ranging from 38.6 to 40.1 meters, suggesting that the fault displaces the middle Pleistocene strata. The exploration findings reveal that the fault is a set of left-lateral strike-slip faults arranged in a NWW direction, resembling a line of geese. This indicates that the southern north China basin has experienced NW-directed strike-slip shearing during the Quaternary, suggesting that the NW-directed tectonic system, controlled by the Qinling orogeny, has remained active since the Quaternary. This has significant implications for analyzing the evolution of the basins in the eastern plains of the north China block.
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Journal of Geodesy and Geodynamics. 2025, 45(5): 456-463. https://doi.org/10.14075/j.jgg.2024.06.267
This article collected seismic waveform data for events of magnitude ML≥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 ML≥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.
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Journal of Geodesy and Geodynamics. 2025, 45(5): 464-469. https://doi.org/10.14075/j.jgg.2024.06.279
Based on the mobile gravity data from Hebei province and its neighboring areas, we select the 2016-06-23 Shangyi MS4.0, 2017-09-04 Lincheng MS3.7, 2018-02-12 Yongqing MS4.3, and 2019-12-05 Fengnan MS4.5 earthquakes to analyze dynamic changes of gravity field. Combining with geological structure information, we investigate the relationship between seismicity and gravity changes. The results show that: 1) For earthquakes of approximately M4, significant pre-seismic changes of gravity field are observed, with notable positive and negative anomaly high-value areas and high-gradient zones, suggesting potential precursor information. 2) Earthquakes tend to occur near fault. The direction of contour lines of high-gradient zones of gravity field is mostly consistent with the orientations of major active fault in the region, indicating a close relationship between earthquakes occurrence, gravity changes, and fault structures. 3) The physical parameters of subsurface media are important for earthquake occurrence. Therefore, it is essential to integrate other disciplines for comprehensive assessments when conducting earthquake prediction.
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Journal of Geodesy and Geodynamics. 2025, 45(5): 470-476. https://doi.org/10.14075/j.jgg.2024.05.260
Based on continuous waveform data from the MS4.7 earthquake in Ar Horqin Banner on October 15, 2021, for three months post-earthquake, machine learning methods were utilized for picking earthquake phases and associating them. The preliminary machine learning-based earthquake catalog constructed includes 386 seismic events, which is 17 times the number of events in the manual catalog of the Inner Mongolia seismic network for the same period. Subsequently, using the P/S phase arrival time information from the event waveforms, a double-difference location method was applied to precisely locate the aforementioned aftershocks and study the seismogenic structure of the earthquake. The results indicate that the aftershocks of the MS4.7 earthquake in Ar Horqin Banner have two main directions of distribution, nearly NW and nearly NEE, within a 1-5 km range around the mainshock. Based on the relocation results and combined with linear geological structures on the topography, it is suggested that there exists an unidentified hidden faults. The distribution of the 4.7 magnitude earthquake and its aftershocks is primarily controlled by the nearly NW-oriented hidden faults and the nearly NEE-oriented structures.
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Journal of Geodesy and Geodynamics. 2025, 45(5): 477-481, 493. https://doi.org/10.14075/j.jgg.2024.05.221
In order to deeply study the dynamic characteristics of muddy soft soil layer in the Jianghan basin, we conduct a series of undrained dynamic tests using a self-vibrating column tester, and analyze the characteristics of dynamic shear modulus ratio G/G0 and damping ratio λ with the change of shear strain γ for the soft soil samples in this area. Different dynamic constitutive models are used to fit the G/G0-γ and λ-γ curves of the muddy soft soil, and the optimal fitting curves are obtained. The results indicate that the nonlinear characteristics of soft soils in the Jianghan basin show strong regional features and are obviously different from the average level in China. The findings can provide more knowledge about dynamic characteristics of the muddy soft soils in this area, and can be used as a reference when the measured dynamic parameters of muddy soft soils are insufficient.
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Journal of Geodesy and Geodynamics. 2025, 45(5): 482-487. https://doi.org/10.14075/j.jgg.2024.06.278
Aiming at the problems of poor positioning accuracy, slow convergence speed, and large influence of clock drift in the case of single-satellite positioning methods, a joint pseudo-ranging/Doppler positioning model with clock-difference correction is proposed, which combines the mathematical model of clock-difference with the pseudo-ranging observation equations and Doppler observation equations, and eliminates the influence of the change of the receiver's clock-difference on the positioning accuracy through the simultaneous estimation of clock drift by the mathematical model of clock-difference and the Doppler observation equations. The proposed method is validated in a simulation scenario, and the results show that the optimal positioning accuracy of the pseudorange/Doppler joint positioning with clock difference correction can reach 219 m under different working conditions, which is 59.4% higher than that of the Doppler localization method; when the pseudorange measurement error is 1 m, the positioning accuracy can be up to 169 m, and the convergence time is around 300 s; when the frequency measurement error is 0.5 Hz, the positioning accuracy can be around 140 m.
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Journal of Geodesy and Geodynamics. 2025, 45(5): 488-493. https://doi.org/10.14075/j.jgg.2024.06.293
The algorithm for solving the geostationary orbit(GEO) using 11 parameters published by the International Telecommunication Satellite Organization(Intelsat) has been extended and applied to the rapid fitting and forecasting of the orbits of four GEO satellites. Firstly, the inverse solution of the 11 parameters is derived in detail. Then, the dynamic prediction of GEO satellite orbits and their onboard GNSS data is simulated. Finally, the accuracy of the orbits with varying fitting and prediction arcs is evaluated. The results show that when fitting data for 6 h, the computation time is less than 0.9 s, and the fitting orbit accuracy is better than 100 m. When using the inverse 11 parameters from different fitting data arcs for prediction, the accuracy of the predicted orbits initially increases and then decreases as the fitting time increases. When the fitting time is 2 days, the prediction orbit accuracy is the highest, and the prediction orbit accuracy of 1 day is better than 1 200 m.
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Journal of Geodesy and Geodynamics. 2025, 45(5): 494-499. https://doi.org/10.14075/j.jgg.2024.05.261
This paper analyzes the orbit determination accuracy and orbit extrapolation accuracy under different gravity field models and finds that the accuracy is higher when the gravity field model order is 100 and 150 compared to when it is 50. In the reduced dynamic orbit determination of GRACE-C and GRACE-D, the 3D directional orbit determination accuracy of EGM2008 and Tongji-Grace02k can reach up to 22.6 mm and 24.0 mm, respectively, both of these gravity field models have better orbit determination accuracy than ITG-Grace03.In orbit extrapolation, Tongji-Grace02k has the highest accuracy, capable of reaching the sub-decimeter level, followed by EGM2008, while ITG-Grace03 has the lowest accuracy, both in decimeter level. Optimizing the random impulse parameters can improve the orbit extrapolation accuracy of the three gravity fields, with the optimization effect being more significant when the model order is 100 and 150 compared to when it is 50.
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Journal of Geodesy and Geodynamics. 2025, 45(5): 500-505, 531. https://doi.org/10.14075/j.jgg.2024.05.251
GNSS-R(global navigation satellite system-reflectometry) technology has been widely verified as an effective means of monitoring ocean tide levels, but the commonly used LSP(lomb-scargle periodogram) spectral analysis method still has issues with low precision and time resolution in storm surge monitoring. This paper, based on observational data from the HKQT station in Hong Kong, China, uses a non-linear fitting method to conduct inversion studies on the storm surge event of Typhoon "Mangkhut" in 2018. By combining wind speed change data during the storm surge period, the paper compares the performance of spectral analysis and non-linear fitting methods in tide level inversion. The results show that the measurement accuracy using the non-linear fitting method is better than 8 cm, with a correlation coefficient of 0.99 compared to the observational data from tide gauge stations. The tide level representation is smoother and more continuous than that of the spectral analysis method, effectively improving monitoring accuracy and time resolution, and providing more reliable technical support for storm surge disaster monitoring.
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Journal of Geodesy and Geodynamics. 2025, 45(5): 506-511. https://doi.org/10.14075/j.jgg.2024.06.289
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.
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Journal of Geodesy and Geodynamics. 2025, 45(5): 512-517. https://doi.org/10.14075/j.jgg.2024.05.223
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 F10.7, 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.
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Journal of Geodesy and Geodynamics. 2025, 45(5): 518-525. https://doi.org/10.14075/j.jgg.2024.05.231
Based on the data of 56 sounding stations in China from 2009 to 2019, we analyze the correlation between precipitable water vapor(PWV) and zenith tropospheric delay(ZTD), water vapor pressure (Es), atmospheric pressure (Ps), surface temperature (Ts), and weighted mean temperature (Tm), and then construct the China PWV models using multiple linear regression (MLR), random forest (RF), multilayer perceptron (MLP), and MLP-RF integration algorithm. The accuracy of these models are evaluated. The results show that the correlation coefficients between PWV and Ts, Ps, Es, Tm and ZTD are 0.78, -0.71, 0.77, 0.74 and 0.99, respectively. The average RMSE of yearly PWV models based on MLR, RF, MLP and MLP-RF are 1.25 mm, 0.44 mm, 0.28 mm, and 0.21 mm, and the average MAE are 0.98 mm, 0.31 mm, 0.18 mm, and 0.14 mm, respectively. The average RMSE of seasonal MLR, RF, MLP, and MLP-RF PWV models are 0.60 mm, 0.45 mm, 0.29 mm, and 0.21 mm, and the MAE are 0.49 mm, 0.33 mm, 0.19 mm, and 0.14 mm, respectively. The yearly MLP-RF PWV model is with the highest accuracy, which is suitable for real time PWV acquisition and research in China region.
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Journal of Geodesy and Geodynamics. 2025, 45(5): 526-531. https://doi.org/10.14075/j.jgg.2024.05.226
High-precision and high-resolution tidal models play a crucial role in the inversion of time-varying gravitational fields, but the published tidal models generally only provide the main tidal components. The fitting coefficient matrix for the secondary tidal components needs to be published by other institutions or calculated independently. This paper first derives the calculation formula for the linear fitting of secondary tidal components in tidal models based on the theory of admittance and tidal potential data. Then, taking the EOT11a, EOT20, and FES2014b tidal models as examples, we calculate the fitting coefficient matrices for the secondary tidal components of each tidal model, as well as the corresponding ocean tide perturbation forces for CHAMP, GRACE, and GOCE satellites for a period of 1 day. Finally, we select the FES2014b tidal model to invert the 120th-order time-varying gravitational field of GRACE-FO for January 2021. The precision and impact of the secondary tidal linear fitting method in this paper are analyzed from different perspectives. The results show that the differences between the fitting coefficient matrices of the three tidal models and the corresponding ocean tide perturbation forces for the three satellites calculated in this paper and the results from the ITSG can be neglected. Considering the secondary tides can improve the precision of gravity potential coefficients above the 40th order and reduce the north-south strip errors in the time-varying gravitational field. The method presented in this paper can provide a reference for independently calculating the impact of secondary tidal components.
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Journal of Geodesy and Geodynamics. 2025, 45(5): 532-544. https://doi.org/10.14075/j.jgg.2024.05.239
Anisotropy exists in the Earth's inner circle, and its genetic mechanism is different.Shear wave splitting can reveal the characteristics of anisotropic media at various depths and structures, providing crucial information for the study of deep Earth dynamics and earthquake prediction. This paper introduces the mechanism of anisotropy in the Earth's interior, summarizes the development of shear wave splitting methods, and the achievements and progress of study the anisotropy of the crust-mantle coupling model by shear wave splitting method.
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Journal of Geodesy and Geodynamics. 2025, 45(5): 545-550. https://doi.org/10.14075/j.jgg.2024.06.286
To address the challenges of traditional hard-threshold methods in dealing with ambiguous boundaries when processing abnormal stations, this paper proposes a new method that treats station anomalies caused by tectonic movements and observational errors as gross errors and uses a membership function to construct an IGGIII equivalent weight function to mitigate the impact of abnormal stations. The new method incorporates fuzzy set theory and is an improved IGGIII robust estimation method based on the membership function of the fuzzy subset to which standardized residuals belong to gross errors(membership function IGGIII, MF-IGGIII). Firstly, the membership function of the fuzzy subset most affected by gross errors in standardized residuals is determined through fuzzy statistics; then, an equivalent weight function is constructed based on these membership function values, and a weight iteration process is performed. Simulation experiments and the fitting analysis of the GNSS velocity field in the Bohai rim area show that this method outperforms hypothesis testing, mean shift methods, and the IGGIII method in abnormal station detection, demonstrating strong capability in identifying abnormal stations.
