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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

To assess the accuracy of Earth rotation parameters(ERP) derived from the current VLBI global observing system(VGOS) observational data, this paper processes data from VGOS observations made between 2019 and 2023. Simultaneously, traditional S-band and X-band VLBI observational data, which were obtained during the same periods as the VGOS data, were also included in the processing. The EOP 14 C04 series provided by the IERS were used as reference values for accuracy assessment. The results show that, during the selected experimental data periods, the average weighted root mean square(WRMS) of the post-fit residuals of time delay from VGOS observational data is 16.77 ps, which is significantly better than the 30.97 ps from the traditional S/X VLBI measurements during the same periods. In terms of ERP determination, there are still differences between the results from global network station observational data of VGOS and traditional S/X VLBI. Specifically, the ERP polar motion component accuracy derived from VGOS is inferior to that of traditional S/X VLBI, while the UT1-UTC accuracy is comparable to that of traditional S/X VLBI measurements. Further analysis using experimental stations centered on co-located stations indicates that VGOS measurements can provide ERP determination results with higher accuracy.

When the measurement noise variance changes in GNSS/SINS integrated navigation system, the estimation function of measurement noise variance and the fault detection function may conflict with each other in Sage-Husa adaptive filtering algorithm. In order to solve this problem, firstly, we design a control factor according to the fault detection function to adjust the estimation model of measurement noise variance of Sage-Husa adaptive filtering algorithm online. Then, according to the characteristics that Sage-Husa adaptive filtering algorithm relies heavily on forgetting factor, a dynamic forgetting factor is designed to accurately track the measurement noise variance, and a Sage-Husa adaptive Kalman filtering algorithm based on double regulatory factors(DRSHAKF) is proposed. Finally, the simulation experiment of integrated navigation system is carried out based on Sage-Husa adaptive Kalman filtering (SHAKF) algorithm with fault tolerance function and DRSHAKF algorithm. The results show that, compared with SHAKF algorithm, DRSHAKF algorithm can organically integrate measurement noise variance estimation function and fault detection function, make full use of useful measurement information, and improve the filtering accuracy.

Inverting the focal mechanism solutions of 708 earthquakes with M_L≥2.0 from January 2009 to February 2023 along the Zhangjiakou-Bohai seismic zone(ZBSZ), we obtained the spatial-temporal distribution characteristics of focal mechanism consistency and the principal stress axes azimuths in this region. By integrating the groundwater level data from Majiagou mine in Tangshan, we analyzed the stress state of the study area. The results indicate that the azimuths of principal stress axes in the western and central sections of ZBSZ have been showing opposite change trends since 1978, while the azimuth in eastern sections has been increasing from 1966 to 2009 and slightly decreasing thereafter. Most of M_L≥4.0 earthquakes in ZBSZ are located in areas with low stress tensor variance. Approximately 70% of M_L≥3.0 earthquakes in the eastern sections of ZBSZ show a decrease in pre-shock misfit values, and stress enhancement phenomena occurred before several M_L≥4.0 earthquakes around the Majiagou mine.

We attempt to apply rock physics-related techniques to study the mechanism of reservoir-induced earthquakes, use the fluid substitution method to calculate the rock porosity in Shanxi reservoir and employ the pore pressure diffusion equation to estimate the pore pressure diffusion coefficient in reservoir area. The results show that: 1) The porosity is maximized in the shallow part of reservoir area within 2 km depth, followed by the southeastern segment of seismogenic fault and minimized in northwestern segment. This distribution feature has a good correspondence with the grouped activity of earthquake sequence, where higher porosity area with better permeability conditions is the region where the first earthquake occurred after reservoir impoundment. 2) The pore pressure diffusion coefficients of earthquake swarms in 2002, 2006, and 2014 are 5.83 m²/s, 8.19 m²/s, and 0.41 m²/s, respectively. This difference has a good consistency with the local variability in rock porosity distribution in reservoir area, indicating that higher pore pressure diffusion coefficient correspond to higher rock porosity. 3) The diffusion rate in epicentral zone is uneven, and the epicentral zone in 2014 was under a higher stress critical state compared to those in 2002 and 2006.

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

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

Based on continuous GNSS observation data, a relatively comprehensive three-dimensional GNSS velocity field for the northeastern margin of the Qinghai-Xizang plateau was established by fully considering random noise and regional environmental loading. This study characterizes crustal strain and vertical motion patterns in the research area. Results show that the region is dominated by compressive strain, with significant differences in principal strain rates between its southwestern and northeastern sectors. Notable distributions of maximum shear strain and principal strain are observed along the east Kunlun fault and Xianshuihe fault. Vertical uplift predominates across the northeastern Qinghai-Xizang plateau, suggesting that vertical tectonic forces may originate from intra-block compressional shortening or obstruction of deep lithospheric material flow. However, significant surface subsidence near the Lanzhou area is likely attributed to collapsible loess and soil erosion. Finally, estimates based on an incompressible Earth model indicate minimal vertical deformation caused by horizontal compression, implying that large-scale uplift in the northeastern Qinghai-Xizang plateau may primarily result from vertical tectonic factors such as lower crustal flow and lithospheric convective thinning, rather than horizontal crustal shortening.

In this paper, the stochastic finite-fault method is used to simulate the ground motion of the Wulong M_S5.0 earthquake. The simulation results for four stations within 100 km of the epicenter showed that the simulated acceleration time histories, peak ground acceleration, and response spectra are generally consistent with the actual records. Some discrepancies were observed at individual stations due to the influence of model parameters and environmental noise. Simulations were performed for 323 grid points within 100 km of the epicenter, and the spatial distribution characteristics of the ground motion obtained were consistent with the intensity field survey data. This study provides data support for seismic fortification and risk assessment in the Chongqing region and has both theoretical and practical significance for mitigating earthquake disasters.

Based on the P-wave travel-time data of 2 538 earthquake events(M_L≥1.0) recorded by 198 fixed stations of CENC from 2019 to 2023, the three-dimensional velocity structure of the crust in this area is inversed by double-difference tomography, earthquake relocation via double-difference tomography and waveform cross-correlation for enhanced accuracy and reliability, it reveals the coupling relationship between crustal structural heterogeneity and seismic activity under the background of craton destruction. The results show that after relocation, the root-mean-square(RMS) of seismic travel time residuals is reduced from 1.09 s to 0.52 s, and the residual average is optimized from －0.33 s to 0.02 s, the accuracy of the velocity model has been improved. Set four profile lines distributed in the Shanxi Jinzhong fault zone, Yanshan structural zone, Tangshan fault zone, Xingtai-Handan fault zone and other fault zones where earthquake events are more concentrated. Velocity structure analysis reveals that most seismic events are clustered within transitional zones between high- and low-velocity anomalies, the crustal thickness exhibits significant lateral heterogeneity. In the volcanic rift basin of Datong, Shanxi province, enhanced thermal-chemical upwelling corresponds to prominent low-velocity anomalies. The Yanshan tectonic zone displays alternating low-velocity and high-velocity anomalies, reflecting unstable stress conditions and structural anisotropy. Multiple strong earthquakes along the Tangshan fault zone predominantly occur within transitional zones between high-velocity and low-velocity anomalies. The Xingtai-Handan fault zone demonstrates concentrated seismic events likely triggered by lithospheric delamination processes associated with high-velocity anomalies.The dynamic mechanism of the destruction of the North China Craton is jointly dominated by lithospheric delamination, thermochemical erosion, and mantle convective erosion induced by the subduction of the Pacific plate, providing new geophysical constraints for understanding the stability evolution of the craton and the mechanism of strong earthquake propagation.

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.

By dividing the seismic cycles of M_S≥7.8 earthquakes in China's mainland and adjacent regions and studying the migration of main active zones, combined with the acceleration-deceleration changes of Earth's rotation speed, this study explores the spatiotemporal patterns and driving mechanisms of M8.0 seismic activity in the study area. The main conclusions are as follows: 1) Since 1879, the study area has experienced 6 active periods of M8.0 earthquakes. The second active period mainly occurred in the Pamir-Baikal seismic belt, the third in the northeastern margin of the Qinghai-Xizang plateau, the fourth in the southeastern margin, the fifth in Yunnan and north China, and the sixth around the Bayan Har block within the Qinghai-Xizang plateau. The region may currently be in the initial stage of a new active period. 2) Since 1867, Earth's length of day(LOD) variation curve shows 4 acceleration-deceleration cycles and 16 acceleration-deceleration phases. The superposition of S tectonic stress fields with deceleration changes favors M8.0 earthquakes in the Pamir-Baikal belt, while NE-oriented stress fields combined with acceleration changes facilitate M8.0 earthquakes along the Qinghai-Xizang plateau margins and interior. The transition from acceleration to deceleration phases causes the tectonic stress field around the Qinghai-Xizang plateau to shift from NE-dominated to locally restored NS orientation, serving as the main driver for the third, fourth, and sixth active periods. 3) The tectonic stress field in China's mainland and adjacent regions has experienced clockwise rotation from NS to NE and then to NEE orientations over the past century, potentially related to Earth's rotation changes involving significant deceleration before 1913 followed by overall acceleration. This process remains ongoing, with no current signs of concentrated M8.0 earthquakes similar to the second active period. However, vigilance is needed regarding possible continued NEE rotation of the Qinghai-Xizang plateau's stress field, and future emergence of new main active zones cannot be ruled out.

In this study, we at first employ a simplified 1-D layered spherical Earth model to compute the co- and post-seismic vertical displacement and geoid change on the seafloor surface due to the 2004 Sumatra earthquake. We then use a pseudo-spectral algorithm to iteratively solve SLE and obtain RSL and geoid changes of long wavelength(>90 km). Results show that the contribution of redistributed seawater mass on RSL is secondary, which can be neglected when we focus on the long wavelength RSL. The effect of geoid change due to the redistribution of seawater mass mainly stems from the self-gravitation of seawater disturbed by earthquakes, while the contribution from elastic load response is an order of magnitude smaller. In addition, we examine two approximate methods of ocean water effect—solving SLE with a uniform ocean covering and Bouguer layer approximation. Comparison results show that both two methods can effectively estimate the co- and post-seismic ocean water effect of the 2004 Sumatra earthquake. The seawater mass effect estimated by Bouguer correction formular is in better agreement with that obtained from solving SLE with a realistic ocean.

We propose an adaptive carrier phase smoothing pseudorange method based on multi frequency observations, which allows for adaptive selection of effective carriers to continue smoothing the pseudorange of all frequencies in the case of partial frequency signal loss of lock or cycle slip. The results show that the adaptive smoothing L1/L2/L5 pseudorange noise of GPS is reduced by about 62%, 50%, and 33% respectively compared to traditional single frequency smoothing, and is reduced by about 60%, 54%, and 61% respectively compared to traditional dual frequency smoothing. In addition, the B1I/B2I/B3I pseudorange noise of BDS-2 is reduced by about 64%, 67%, 51% respectively compared to traditional single frequency smoothing, and is reduced by about 55%, 59%, 50% respectively compared to traditional dual frequency smoothing. Similar effects are also observed in other GNSS frequencies. Conducting dynamic positioning experiments on road overshadowed by trees and tall buildings, the results indicate that standard deviation(STD) of adaptive smoothing pseudorange positioning is reduced by about 45%, 76%, 47% in E, N, U directions respectively compared to single frequency smoothing and about 41%, 69%, 49% compared to dual frequency smoothing. Adaptive smoothing method can improve position accuracy effectively.

Time series InSAR deformation may be affected by the atmospheric residual effects caused by seasonal differences and weather changes(such as precipitation and snowfall), thereby reducing its accuracy. Taking Tianjin city as an example, we conduct research on the atmospheric residual effects and their correction of time series InSAR deformation. First, the SBAS-InSAR technique was used to process Sentinel-1A images to obtain time series InSAR deformation. Then, the time series InSAR deformation was compared with precise leveling measurement results, and the atmospheric residual effects in time series InSAR deformation were analyzed combining with seasonal and weather change characteristics. Finally, an atmospheric residual error model was constructed based on ERA5 PWV data, which was used to remove the atmospheric residual effect errors to optimize the time series InSAR deformation. The results show that time series InSAR deformation has atmospheric residual effect errors, especially those caused by weather changes such as precipitation, which is more pronounced and affect the accuracy of time series InSAR deformation. There is a significant negative correlation between the difference of monthly time series InSAR deformation and monthly precise leveling deformation and the PWV changes in the same period. The atmospheric residual effect correction model constructed using the linear regression method can effectively improve the accuracy of time series InSAR deformation.

The second and third generation of non-dominated sorting genetic algorithm(NSGA-Ⅱ, NSGA-Ⅲ), multi-objective grasshopper optimization algorithm(MOGOA), multi-objective gray wolf optimizer(MOGWO), multi-objective ant lion optimizer(MOALO), and multi-objective evolutionary algorithm based on decomposition(MOEA/D) are introduced to construct multi-objective localization optimizations functions using two different classical microseismic inversion mathematical models. Based on the comparative testing of microseismic event data in deep-mining mine and manual simulation data, the effectiveness and reliability of six multi-objective localization algorithms are analyzed. The results show that the performance of six multi-objective localization models varies. The mean error of 100-round microseismic source localization of MOALO based on the polyhedral array simulation is 1.242 5 m, while the mean error of microseismic source localization of NSGA-Ⅱ based on deep-mining mine is 162.569 1 m. The robustness of MOGOA, based on Shizhuyuan mine microseismic event, is superior to that of MOALO. Considering multiple performance indices, including localization accuracy and model reliability, it is believed that MOGOA has strong application prospects for engineering physical exploration and microseismic monitoring.

We explore estimation methods of seismic tsunami hazard based on the generalized extreme value theory, provide two case studies for constructing seismic activity models: one based on the generalized extreme value distribution to build a seismic activity model for Ryukyu trench subduction zone, and the other based on the generalized Pareto distribution to build a seismic activity model for Manila trench subduction zone. Six specific sites along the southeast coast of China are selected, and strong seismic activity models are constructed using generalized extreme value theory, considering the Manila trench and Ryukyu trench subduction zones as potential source areas. Through numerical simulation of seismic tsunamis, the estimation result of seismic tsunami hazard for these specific sites of Manila trench and Ryukyu trench subduction zones in a future time period is obtained. These results are then compared with estimation results that consider the uncertainty effects. The findings indicate that the ranking of deterministic estimation results is consistent with that of coupled uncertainty effects, with the former having higher values than the latter, but still having reference value.

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.

We investigate the phenomenon of coseismic ionospheric disturbances(CIDs) caused by Japan Noto Peninsula M_W7.6 earthquake on January 1, 2024 using the total electron content(TEC) calculated by GPS observation data. The results show that: 1) Satellite G04, located northwest of earthquake epicenter, recorded a CIDs with maximum disturbance amplitude of approximately 0.07 TECu. 2) Satellite G16, located east of earthquake epicenter, recorded a CIDs with maximum disturbance amplitude of about 0.08 TECu. 3) The G16 and G26 satellites detected more significant CIDs in south of earthquake epicenter than in other directions, which is consistent with the direction of seismogenic fault(southwest direction). Significant CIDs are also detected at Kokubunji station, located about 286.714 km south of earthquake epicenter. This significance may be due to the large vertical displacement of thrust type earthquakes, which increases the disturbance amplitude of CIDs signal. 4) The CIDs detected by G04, G16 and G26 satellites have the propagation velocities of about 589 m/s, 623 m/s, 876 m/s and 829 m/s, and the corresponding center frequencies are about 3.14 MHz, 2.9 MHz, 2.9 MHz and 2.9 MHz in the northwest, east and south of earthquake epicenter, indicating that the ionospheric disturbances detected in different regions are consistent with the characteristics of ionospheric disturbances excited by seismic waves.

To enhance the filtering performance of the maximum correntropy Kalman filter(MCKF) method in complex environments, an adaptive maximum correntropy Kalman filter algorithm(AMCKF) for GNSS/SINS integrated navigation systems is proposed. Firstly, based on the relationship between the filtering fault detection function values at the current and the past (l-1) time steps and the detection threshold, two mapping relationships of 0 and 1 are formed. Then, a window of length l is constructed using the mapped values, and a kernel width adaptive adjustment algorithm is proposed. Finally, this kernel width adaptive adjustment algorithm is applied to MCKF to form the AMCKF algorithm for the integrated navigation system. Experiments are conducted on a GNSS/SINS integrated navigation system under measurement environments with Gaussian white noise and heavy-tailed impulsive noise. The results indicate that AMCKF can adaptively adjust the kernel width value according to different measurement noise environments, thereby improving the filtering accuracy of the integrated navigation system. Compared with KF and MCKF, AMCKF can improve position accuracy by approximately 26.5% and 16.4%, respectively, and improve velocity accuracy by approximately 15.5% and 6.4%, respectively.

To address the issues of large pseudorange measurement noise, discontinuous observation data, weak geometric strength in smartphone GNSS observations, and high noise levels in the built-in micro inertial measurement unit(MIMU) of smartphones, a tightly coupled GNSS/MIMU navigation method enhanced by low-Earth orbit(LEO) satellites is proposed. Based on the characteristics of the Walker constellation and the Keplerian orbital parameters of LEO satellites, LEO pseudorange observation data are simulated. The positioning performance of smartphone GNSS single-point positioning, GNSS/MIMU tight integration, and LEO-enhanced GNSS/MIMU tight integration are compared and analyzed. Real smartphone data are used for validation. The experimental results show that after incorporating LEO satellites, the average number of visible satellites increases by about 7. The faster movement speed of LEO satellites further optimizes the GNSS geometric strength, reducing the average PDOP value by 50%. Compared with GNSS single-point positioning, the GNSS/MIMU tight integration improves positioning accuracy in the east, north, and up directions by 18%, 23%, and 10%, respectively. The LEO-enhanced GNSS/MIMU tight integration improves positioning accuracy in the east, north, and up directions by 73%, 81%, and 60% compared with GNSS single-point positioning, and by 67%, 75%, and 56% compared with GNSS/MIMU tight integration.

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.