The quadratic polynomial(QP) model in satellite clock offset prediction is susceptible to noise interference and the prediction accuracy is not high, so we construct a multi-GNSS satellite clock offset prediction model based on long short-term memory neural network. We analyze the model accuracy of different satellite systems and different clock types based on different modeling schemes. To verify the validity and feasibility of the model, we use the LSTM, QP, and QP-LSTM models to forecast the clock offset with 1 h, 3 h, 6 h, and 12 h based on 12 h and 24 h clock offset series, respectively. The results show that the LSTM model has the highest accuracy with 24 h modeling data for 1 h prediction. In the LSTM prediction model of multi-GNSS satellite clock offset, the Galileo system has the highest accuracy, followed by the BDS-2 system and GPS system, and the GLONASS system has the lowest accuracy, with STD of 0.018 ns, 0.069 ns, 0.133 ns, and 0.242 ns, respectively. The prediction accuracy of different types of atomic clocks varies. The prediction accuracy of hydrogen atomic clock is better than Rb atomic clock and Cs atomic clock. The prediction accuracy of LSTM neural network model is improved by 27% compared to QP-LSTM model and 36% compared to QP model.

By employing the Bayesian three-cornered hat method, we integrate multiple GRACE/GRACE-FO reconstruction models and improve the precision of the reconstruction models using deep learning methods. This approach provides valuable guidance for accurately filling the data gaps in GRACE/GRACE-FO missions. The experimental results show that the combined model exhibits the lowest uncertainty in global terrestrial water storage changes and maintains better agreement with the reference model in most basins. When compared to the optimal individual model, the combined model demonstrates superior performance in semi-arid, semi-humid, and humid regions, with a significant 15% reduction in overall uncertainty and an approximate 5% enhancement in Nash-Sutcliffe efficiency for both global and basin-scale terrestrial water storage changes.

Based on the geometry model of plane fault, taking the 2013 Lushan M_S7.0 earthquake as an example, we use the spectral element method to investigate the topographic effect on coseismic deformation. The results show that the influence of topographic effect on coseismic deformation in different directions varies. For the horizontal displacement component, the maximum influence along the fault strike is about 10.3%, while along the vertical fault strike is about 12.4%. For the vertical displacement component, the maximum influence is about 11.9%. Therefore, it is essential to fully consider the influence of topographic effect when calculating surface coseismic deformation or performing finite fault inversion.

Based on GPS displacements, we apply the finite fault method to inverse the slip distribution of the 2022 Taiwan M_W6.9 earthquake. The results show that the earthquake ruptured to the surface, and the slip is dominated by strike-slip with a reverse component. It mainly extends along the fault in the NNE direction. There are two rupture concentrated areas, and the total released seismic moment is about 5.73×10¹⁹ Nm. Based on the analysis of the GPS observations and dislocation theoretical model, we infer that the coseismic deformation generally conforms to the regional tectonic movement characteristics of the east coast of Taiwan island. The subduction of the Eurasian plate by the Philippine sea plate is the main source of power for the Central Range fault activity.

Based on four phases of GNSS crustal movement velocity fields from 1999 to 2007, 2009 to 2013, 2013 to 2017 and 2017 to 2021, we analyze the current differential movement characteristics of each secondary fault by constructing GNSS velocity profiles. Furthermore, we establish a negative dislocation model to invert the current locking degree and slip deficit rate of each secondary fault. The results show that: 1) The northern margin fault of west Qinling mountains currently presents the activity characteristics of sinistral strike-slip and thrust extrusion. 2) From 1999 to 2007, the Guomatan section and Tianshui-Baoji section were all in a strong locking state, while the Zhangxian section and Yuanfeng section were only partially locked with low degree and shallow depth. From 2009 to 2013, the locking degree of middle section of northern margin fault of west Qinling mountains was weakened. The eastern Yuanfeng section and eastern Tianshui-Baoji section changed from strong locking to creep state, while the Guomatan section and central and western  Tianshui-Baoji section still showed strong locking state. From 2013 to 2017, the northern margin fault of west Qinling mountains was in a strong locking state, and only the eastern Tianshui-Baoji section was in a creep state. From 2017 to 2021, the central and western Guomatan section, Zhangxian section, eastern Yuanfeng section, and central Tianshui-Baoji section were in a strong locking state, while the central Yuanfeng section and western Tianshui-Baoji section were in a creep state. 3) The overall distribution characteristics of slip deficit rate of each secondary fault are basically consistent with the locking degree. The Guomatan section and central Tianshui-Baoji section of northern margin of west Qinling mountains are in a strong locking state and have a strong background of strain energy accumulation.

Aiming at the problem that the traditional synthetic aperture radar interferometry technology is greatly affected by tropospheric delay when monitoring surface deformation, we use the measured meteorological parameters and NCEP meteorological reanalysis data to establish atmospheric correction models respectively. The tropospheric delay correction is performed on the interferogram generated in Yinzhou District to obtain high-precision surface deformation in Yinzhou District from 2018 to 2020. To analyze the effect of different atmospheric correction models on weakening the tropospheric delay effect, we compare the monitoring results with the measured level data in the same period. The results show that the RMSE of the ground meteorological information model, the NCEP meteorological reanalysis data model, and the InSAR monitoring results without atmospheric correction are 2.78 mm, 3.86 mm, and 5.62 mm, respectively. The results further show that the use of the ground meteorological information model to correct the atmospheric phase error has higher monitoring accuracy and can effectively weaken the influence of tropospheric delay on interferometry results.

This paper focuses on the data processing analysis of 2020 mount Qomolangma height measurement. First, we detail the process of calculating the 2 important values used to calculate the elevation of the summit of mount Qomolangma, and then we present the height of mount Qomolangma jointly by China and Nepal based on the international height reference system(IHRS): 8 848.86m. Finally, this paper summarizes the characteristics of the achievements, and describes its high accuracy and reliability.

Due to the influence of GNSS hardware equipment, communication link, and observation environment, GNSS displacement monitoring data often contains gross errors, which cannot reflect the real deformation characteristics. In order to solve this problem, we propose to apply the robust random cut forest(RRCF) algorithm to real-time GNSS displacement gross error detection. The simulation data processing results show that the accuracy, precision and recall rate of real-time gross error anomaly detection of RRCF algorithm are better than 95%, 98% and 96%, respectively. The results of geohazard displacement monitoring data show that when outliers occur in GNSS displacement monitoring data, the detection results of RRCF method are in good agreement with the actual outliers, and have a low misjudgment rate. Overall, the RRCF algorithm can provide relatively high accuracy and availability for real-time outlier detection of GNSS displacement monitoring data.

Aiming at the problems of low positioning accuracy and poor reliability in areas without CORS services, we propose a method for differential positioning using a self-established base station with smartphone. The method uses an external antenna to improve the quality of GNSS observation data and uses devices such as RF shielding boxes to set up a self-established base station. The Huawei Mate40 smartphone is used as a mobile station, and RTK positioning is performed with both traditional CORS base station and self-established base station. Static, walking, and cycling experiments are designed to evaluate the service capability of self-established base station. The experimental results show that in the static experiment, the RTK positioning accuracy of Huawei Mate40 smartphone with self-established base station can reach centimeter-level accuracy. In the dynamic experiment, the RTK positioning accuracy of Huawei Mate40 smartphone with both self-established base station and CORS reference station can reach decimeter-level accuracy, with a difference in planar positioning accuracy of about 0.1 m between the two methods. The self-established base station based on a smartphone can provide stable reference station services and meet the needs of surveying and mapping work in specific scenarios.

Starting from the system state model, we analyze the influence of scale factor error on the calculation amount and accuracy of integrated navigation. At the same time, based on the characteristics of vehicle motion, we analyze the observability of the scale factor error, and propose a dimensionality reduction state model that only retains the scale factor errors of the heading gyroscope and horizontal accelerometer. The experiments show that: when the scale factor error is greater than 6×10^-3, augmenting the scale factor error can help improve navigation accuracy, but the calculation amount increases by about 170%; the reduced-dimensional model can achieve the navigation accuracy of the high-dimensional model, and the calculation amount is only increased by about 70% compared to that without augmenting scale factor error.

We use the double difference method to accurately locate small and medium-sized earthquakes in the Taiyuan Basin and establish the sub-area of hidden faults in Taiyuan basin. By using the magnitude frequency relationship model reduced by a certain time scale, we fit the empirical evaluation model between the maximum earthquake magnitude Mmax of the hidden fault in Taiyuan basin and the magnitude frequency relationship at/b parameter. After comprehensive analysis, we give the upper limit prediction value of potential magnitude of each active fault zone. To predict the probability of occurrence of potential maximum earthquake magnitudes and moderate-strong earthquake magnitudes for each hidden active fault, we use the Poisson probability model. The results indicate that the Tianzhuang-Wenshui-Fenyang fault area in the central and western parts of the basin, as well as the Sanjia-Hongshan-Pingyao fault area in the southeastern part of the basin, have a higher probability of future earthquakes with M_S≥6.5, while the probability level of earthquakes with M_S≥6.0 occurring in the future in the Qizishan and Beitian-Wanghu fault areas, mainly composed of NW trending hidden active faults, is relatively low.

By combining chaotic mapping and adaptive inertial weight, we improve the standard whale algorithm so as to improve the global optimization ability and convergence speed of the algorithm. Aiming at the disadvantage of BP neural network, we use the improved whale algorithm to optimize BP neural network. On this basis, we establish the improved whale algorithm to optimize the BP neural network GPS elevation anomaly fitting prediction model, and the model is verified by two groups of GPS data in different terrain feature engineering. The results show that the BP model optimized by the improved whale algorithm can achieve higher accuracy and stability in GPS height fitting.

We take Xi’an-Xianyang region as the study area and use Sentinel-1A satellite data covering the study area from June 2015 to January 2023. Using time-series InSAR as the main technical means, combined with other data, we obtain information such as the distribution characteristics and deformation velocity of land subsidence in Xi’an-Xianyang area, and analyze the laws of land subsidence occurrence and evolution. The results show that the results obtained by SBAS-InSAR and StaMPS-InSAR are basically consistent. The ground deformation areas in Xi’an are mostly central and southern, and the main factor of deformation is groundwater exploitation. The distribution and trend are influenced by ground fissures and faults. Most areas of Xianyang are in a stable state, with only some areas experiencing significant deformation, which is influenced by various factors such as groundwater exploitation and urban construction.

To quantitatively analyze the influence of BDS-3 observation multipath error on deformation monitoring accuracy, we select 128 d of BDS-3 monitoring data of a water conservancy project containing 7 stations in 2022, and study the correlation between BDS-3 observation multipath error, deformation monitoring accuracy before and after branch cutting of trees around the monitoring stations. The results show that 1) there is a strong correlation between multipath error and BDS-3 deformation monitoring accuracy, and the correlation coefficients with plane and elevation accuracy are greater than 0.93 and 0.81, respectively; 2) the average multipath error using B1I and B3I observations after tree branch cutting around the monitoring site is reduced from 0.676 m and 0.426 m to 0.329 m and 0.230 m, and the average monitoring accuracy in N, E and U directions reaches 0.9 mm, 0.8 mm, 1.7 mm, and 1.1 mm, 1.0 mm, and 2.2 mm, respectively, which is 63%, 69%, 58%, and 52%, 61%, and 48% higher than that before cutting branches; 3) after changing the surrounding observation environment to weaken the influence of multipath error, the accuracy of using B1I observations is better than that of using B3I observations. Therefore, in the BDS-3 short baseline deformation monitoring application, B1I observations are recommended.

To test the performance of an under construction time keeping system, we propose a remote evaluation method based on GNSS carrier phase and conduct experimental verification. Taking the national standard time UTC(NTSC) as reference, and based on the GNSS observation data of four stations in Xi’an and Beijing for a continuous 15 days, we use PPP and carrier phase common-view(PCV) methods to calculate the time deviation of time keeping system relative to UTC(NTSC). Then, we analyze the relative frequency deviation and frequency stability of time keeping system. The results show that the system error of PCV and PPP time transfer links is small, and the accuracy of time transfer is high. The PCV and PPP time transfer can accurately measure the frequency stability and relative frequency deviation of time keeping systems that are far away from each other. The research results can lay a solid foundation for the remote evaluation of time keeping system performance.

For the South China Sea region, we use three types of gravity field signals(vertical deflection, gravity anomaly, and vertical gravity gradient anomaly) to train a convolutional neural network model, which is compared and analyzed with shipborne depth and foreign models. The three gravity signals are divided into four groups: gravity anomaly, gravity anomaly combined with vertical gravity gradient anomaly, gravity anomaly combined with vertical deflection, and gravity anomaly combined with vertical deflection and vertical gravity gradient anomaly. The standard deviations between the inversion results of four combinations and shipborne depths are 104.780 m, 102.778 m, 93.788 m, and 88.289 m, respectively, indicating that the accuracy of bathymetry prediction improves significantly with the increase of different types of gravity data. At depth greater than 2 000 m, the accuracy improvement of inversion results is more significant. By setting the proportion of training set to total dataset to 80%, 70%, 60% and 50%, respectively, the standard deviations between the inversion results and shipborne depths are 88.289 m, 91.256 m, 92.833 m and 96.022 m, respectively, indicating that the increase of data can effectively improve the accuracy of model learning results.

To effectively grasp the reactivation characteristics and deformation laws of an ancient landslide, based on the on-site investigation results of the landslide area, we analyze the reactivation deformation characteristics, and then use the WPT-ROA-RVM-CT model for landslide deformation prediction. The results show that after heavy or continuous rainfall, the surface cracks of landslides are relatively developed, with tensile and shear properties. The landslide exhibits obvious displacement characteristics, that is, the deformation of the middle and rear edges of the landslide are significantly greater than that of the front edge. The deformation direction has a counterclockwise variation, fully indicating that the reactivation deformation characteristics of ancient landslides are significant. Meanwhile, through deformation prediction, the WPT-ROA-RVM-CT model is verified to have high prediction accuracy. Through extrapolation prediction, we find that the subsequent deformation rates of landslides are all positive and large, indicating that the subsequent deformation of landslides will further increase, with a significant risk of instability. Therefore, disaster prevention and control research need to be carried out as soon as possible.

On the basis of the reconstructed single difference residual of carrier phase, we estimate the multipath repetition time of Beidou satellite by using the segmentation idea; we then extract the multipath of single difference residual of carrier phase by regularization method and classical wavelet filtering method respectively to obtain a “clean” single difference residual sequence. The experimental results show that Tikhonov regularization is feasible to correctly extract the multipath signal, the multipath signal is smoother than the original residual measurement, and the estimation method of the regularization parameter is further optimized. After using the optimized Tikhonov regularization method and sidereal filtering, the single difference residual of carrier phase is improved by 40.5% on average. The coordinate residual in E, N and U directions are improved by 24.8%, 26.3% and 42.7%, respectively. The optimized Tikhonov regularization is superior to the traditional wavelet filtering method in both the observation and coordinate domains.

We first obtain the coseismic deformation of the Tajikistan M_W7.2 earthquake based on the ascending and descending Sentinel-1A SAR images. The coseismic deformation shows that the maximum displacement are 15 cm and 16 cm for ascending and descending tracks, respectively. Then the fault geometry and slip model are inverted based on the elastic dislocation model with the InSAR data as constraints. The best-fitting fault geometry parameters are 131.1° for strike and 85.7° for dip angle. This event is dominated by right-lateral strike-slip motion and has not ruptured to the surface. The slip asperity is concentrated at the depth of 10 to 30 km with a maximum slip of 3.49 m. The seismic moment magnitude is about M_W7.16. Finally, we calculate the static Coulomb stress change at different depths and adjacent faults using inversion slip model. The results suggest that the magnitude of Coulomb stress change increases with depth, which is consistent with the existing stress field and geological investigations of Pamir plateau. The aftershock activity begins to occur at a depth of 10 km. Furthermore, the Coulomb stress change induced by this event has little effect on the adjacent faults.

In order to study the coseismic deformation and seismogenic fault slip characteristics of the conjugate earthquakes sequence that occurred in the east Anatolian fault system on February 6, 2023, we use D-InSAR and POT techniques to obtain the coseismic deformation field of the earthquake sequence with the Sentinel-1A data released by ESA. Based on the distributed slip model, we study the geometric form and refined slip distribution inversion of seismogenic faults after data quadtree down-sampling. The results show that the deformation trend of coseismic deformation field of the conjugate earthquakes presents an opposite change trend, and the seismogenic faults are located in the east Anatolian fault system dominated by left-lateral strike-slip. The rupture fault of M_W7.8 earthquake is on the main fault zone, with a maximum slip momentum of about 10.5 m and an average slip angle of 3.74°. The rupture fault of M_W7.5 earthquake is mainly on the Sügür fault, with a maximum slip momentum of about 11.8 m and an average slip angle of 1.05°. The joint analysis on focal mechanism solution given by USGS and GCMT shows that the two major earthquakes are mainly left-lateral strike-slip earthquakes with a small dip-slip component, and the occurrence of this earthquake sequence is an important manifestation of the present tectonic movement of east Anatolian fault zone.

We propose a time accuracy measurement method for low-sampling data acquisition equipment. We introduce the measurement principle and data acquisition process of this method, and give results of the time accuracy for a low-sampling data collector equipment with an example of earthquake department. The results show that this method can improve the time measurement accuracy of low-sampling data acquisition equipment to milliseconds. This method can be used in the test of timing accuracy of geophysical observation data collector with linear relationship between input and output.

Based on the high density electrical inversion results, we investigate and study the trace distribution and structural features of Sumatou fault combing with drilling, exploration well and other engineering survey methods. We observe the terrain of Sumatou fault, and conduct ¹⁴C dating of stream terraces. The dating result is 13 436±210~40 724±6 332 a, indicating that the Sumatou fault has not been active since the late Pleistocene. It is concluded that the Sumatou fault is an NNE trending buried fault with a strike of about 25°, a tendency of SE, a dip angle of about 65°, and a fractured zone width of about 20 m. The latest active age of Sumatou fault is the middle Pleistocene.

The sparrow search algorithm(SSA) is used to optimize the variational mode decomposition(VMD), then combining wavelet decomposition(WD), we propose a GNSS coordinate time series noise reduction method(IVMD-WD). This article conducts experiments using simulated signals and measured data from 10 reference stations.The results show that compared with empirical mode decomposition(EMD), ensemble empirical mode decomposition(EEMD) and WD, the IVMD-WD method has the best noise reduction effect, it can more effectively eliminate noise in the GNSS coordinate time series.

The positioning accuracy and reliability of multi-sensor integrated navigation can be improved by making full use of prior constraint information. We extend Kalman filtering under state constraints to traditional federated filtering and propose a federated filtering algorithm under state constraints. When the sub-sensor is abnormal, we use Huber method to adjust the observed noise matrix of the sub-filter based on federated filtering under state constraints. Meanwhile, we introduce adaptive information sharing factor in the information sharing stage to dynamically adjust the fusion weight of the sub-filter and obtain a robust and adaptive federated filtering algorithm with state constraints, which further reduces the impact of inaccurate sub-filter estimates on the fusion results. The method is applied to the multi-sensor integrated navigation system of strapdown inertial navigation system, GNSS and odometer. The simulation results show that the estimation accuracy of federated filter under state constraints is better than that of traditional federated filter, and robust adaptive federated filtering can further improve the accuracy and reliability of navigation and positioning under abnormal observations.

Global navigation satellite system(GNSS) coordinate series accuracy is mainly affected common mode error(CME) influence. In order to improve the accuracy of GNSS coordinate series, this paper adopts variational bayesian independent component analysis(vbICA) method to extract CME of coordinate series of 20 GNSS stations in the experimental site, and uses distance correlation coefficient and root mean square(RMS) as indicators to evaluate the filtering effect of the original coordinate series. The filtering performance of vbICA method is compared with PCA and ICA. The results show that the filtering effect of vbICA is obviously better than PCA and ICA. After vbICA filtering, the RMS of residual coordinate series in E,N,U direction decreases by 36.57%, 31.63% and 10.97% on average. Distance correlation coefficient decreased by 60.53%,56.84% and 25.80% on average. Considering the optimal noise model and excluding CME, GNSS velocity field estimation is more reliable and accurate, effectively improving GNSS coordinate series accuracy, and providing reliable data support for geodynamic research.

We take the typical surface rupture caused by the Luhuo M7.9 earthquake in 1973 as an example. Based on the UAV SfM method, we obtain high resolution and high precision topographic and geomorphic data in the region. We extract the quantitative parameters of dislocation by LaDiCaoz and introduce the relevant technical process in detail. The results show that: 1) The horizontal dislocation and vertical dislocation of typical ridge dislocations in Luho Zhajiao village area measured by LaDiCaoz are 6.3(+0.5/－0.7) m and 0.4(+0.1/－0.1) m. The analysis shows that the amount of horizontal dislocation is the cumulative result of 3 strong earthquakes at least. 2) UAV SfM method can obtain high resolution and high precision topographic and geomorphic data in a small area efficiently, conveniently and at a low cost. The data quality can satisfy the fine structure study of active faults and quantitative parameter extraction, which has a broad application prospect in the high altitude of western Sichuan. 3) Using LaDiCaoz for dislocation extraction can further reduce the error of measurement results caused by human factors, and the reliability of dislocation results can be verified, realizing the semi-automatic extraction of active fault dislocation.

We study the data of Maduo M_S7.4 earthquake in Qinghai province on May 22, 2021 recorded by second sampling YRY-4 borehole strain gauge and the resampling seconds of BBVS-120 seismometer observed at Gaotai station. We carry out comparative analysis of data variation characteristics, seismological phase morphology and spectral characteristics. We find that the coseismic record of borehole strain second sampling data is clear, and the coseismic record satisfies the self-check characteristics of the four-component borehole strain observation. Both sets of instruments can record the seismic phase of the earthquake, the seismic phase morphology is similar, and the seismic phase arrival time is basically the same. The frequency spectrum and time-frequency diagram of the two sets of instruments are similar, the spectrum components are close, but the frequency distribution and amplitude change are different. This is related to the observation principle, component(direction finding) orientation, frequency bandwidth and observation sensitivity of the instrument. To further analyze the dynamic significance of borehole strain, we conduct space projection of borehole strain at different time nodes, and combined with the relative orientation of the earthquake epicenter and the station, we find that the southwest northeast 2323 and 2324 components, which are approximately close to the epicenter pointing station, and the 2321 and 2322 components distributed perpendicular to the epicenter pointing station, are in opposite tension and compression states. This may be related to the propagation laws of P and S waves.

Based on the superconducting gravimetric observations at Yichang seismic station in 2017, we obtain the accurate local gravity tidal parameters of Yichang station by harmonic analysis of observation data after data preprocessing, polar motion correction and long-period trend correction. We select the NAO.99b and osu.Chinasea.2010 ocean tide models to study the influence of ocean tide loading on gravimetric observation. The results show that the amplitude change of ocean tide loading at Yichang station is about 25 nm·s^-2, and the tidal parameters improve after ocean tide loading correction. We use the time-domain admittance method and global atmospheric model ERA-Interim to calculate the atmospheric loading effect of Yichang station. The results show that the atmospheric gravity admittance factor of Yichang station is -3.219 3 nm·s^-2·hPa^-1. The amplitude change of atmospheric gravity loading in the near region is about 160 nm·s^-2, and can reach 70 nm·s^-2 in the far region. The global atmospheric loading effect cannot be ignored when processing and analyzing superconducting gravimetric data.

Based on gravity data, with aims to evaluate the effectiveness of Bayesian inference for subsurface target detection in situations where the spatial position and shape of underground targets are unknown, we perform modeling and analysis in terms of regional measurement and line measurement scenarios. The results show that Bayesian method for gravity gradient detection outperforms microgravity detection and can lead to a good parameter prediction quality.

We propose a GNSS instantaneous clock offset model construction algorithm considering parameter sparsity. The algorithm is constrained by adding L1 norm term(Lasso) to the least squares polynomial fitting, and the clock offset model is fitted by sliding modeling, that is, sliding Lasso fitting method. Using GFZ 300 s clock offset products as training data, the regularization parameters are obtained through 10-fold cross-validation, and the clock offset model is established. The satellite clock offset fitting accuracy and PPP accuracy are compared with the commonly used clock offset densification algorithm. The experimental results show that the sliding Lasso fitting method can effectively eliminate the influence of excessive jump of clock offset in local clock offset data during the fitting process, prevent the model from overfitting, and improve the fitting accuracy and PPP accuracy of the clock offset model.

We analyze the characteristics and changes of system time offset parameters of each GNSS, and compare and evaluate the broadcast system time offsets according to the data published by BIPM and the time and frequency bulletin, respectively. The results show that there is a bias of more than 10 ns in the system time offsets of GPS/GLONASS/Galileo broadcasted by BDS. The accuracy of system time offsets between GLONASS and GPS, as well as Galileo and GPS, obtained indirectly through BDS, are better than that of the same parameters broadcasted by GLONASS and Galileo.

In order to further test the tracking indicators of microwave fluctuation impending earthquake, based on the data from real-time monitoring and tracking system of microwave fluctuation impending earthquake in Lanzhou, we analyze the waveform data recorded by stations within 150 km of earthquakes of magnitude 5.0 and above in Qinghai region from 2020 to 2022. We believe that almost all stations within a radius of 150 km from the epicenters can record impending microwave motion events. The stations that achieve the index of microwave fluctuation impending earthquake anomalies are not the closest to the epicenter. This may be related to regional tectonic stress, strike of seismogenic fault and process of earthquake rupture. Moreover, the larger the magnitude of the main earthquake, the greater the likelihood of the occurrence of the index of microwave fluctuation impending earthquake anomalies.

We construct a three-dimensional viscoelastic finite element model of the eastern boundary fault zone of the Sichuan-Yunnan block. We calculate long-term average tectonic stress loading rate of the main faults with GNSS observation data as a constraint. According to the historical earthquake rupture models, we calculate the co- and post-seismic Coulomb stress changes in Xianshuihe fault zone, Longmenshan fault zone and so on. Then, we obtain the total stress evolution of the main fault zone in the study area. The results show that the tectonic stress loading rate on Xianshuihe fault zone, the southern section of Daliangshan fault zone, and Litang fault zone are high, which can reach 1.0 to 1.5 kPa/a. In addition, the tectonic stress accumulation in the 2022 Luding M_S6.8 earthquake rupture area is about 0.177 MPa during the seismic recurrence cycle, and the historical events produced 0.07 MPa stress loading. The two stress accumulations together led to the Luding earthquake’s occurrence. In addition, the total stress accumulation on the Anninghe fault zone seismic gap area since the occurrence of the previous event(about 487 years ago) is about 0.3 MPa. The last rupture events occurred about 1 000 years ago in the southern section of Daliangshan fault zone and Litang fault zone, and the total stress accumulation in the seismic recurrence cycle is more than 1.0 MPa, which may indicate that these areas have greater seismic activity potential.

The real-time observation data transmitted by BNC(BKG NTRIP client) is used to evaluate and analyze the positioning performance of GPS and QZSS in the Asia Pacific region from the number of visible satellites, position dilution of precision(PDOP), multipath effect, signal-to-noise ratio, real-time relative positioning accuracy, etc. The results show that after combining QZSS with GPS system, the number of visible satellites increases, the geometric configuration of satellites is better, and the availability and reliability of positioning accuracy improves. The variation pattern of the multipath effect of QZSS satellites is consistent with that of GPS satellites, and the multipath error of each frequency point of QZSS satellites is mostly smaller than that of GPS satellites. The signal-to-noise ratio and altitude angle variation trend of each frequency point of GPS and QZSS satellites are basically the same. In the N, E, and U directions, the real-time relative positioning accuracy of the GPS/QZSS combination is improved compared to GPS.

Based on observation data from the National Geomagnetic Network Center, we study the relationship between the geomagnetic low-point displacement anomaly and earthquakes above 5 magnitude in the mainland of China in the 10 years from 2013 to 2022. The results show good correlation between the geomagnetic low-point displacement anomaly and earthquakes above 5 magnitude. There is high probability of earthquakes with magnitude greater than 5 within 300 km of the anomaly boundary within 2 months after the occurrence of geomagnetic low-point displacement anomaly. The results show that 160 main earthquakes with MS≥5 occurred in mainland China in 2013 to 2022, with an anomaly correspondence rate of 32.4%, the false alarm rate of 67.5%, the false negative rate of 48.1% and the earthquake prediction rate of 55.0%. There is one low-point displacement anomaly before 46 earthquakes, and two or more anomalies before 42 earthquakes. The study also found that superimposing multiple low-point displacement anomaly boundaries before an earthquake on the same base map will form one or more intersection areas, and earthquakes often occur in the intersection area of the low-point displacement boundary. Based on the distribution of active tectonic faults, the occurrence of historical large earthquakes, the potential danger zone of strong earthquakes predicted in the medium and long term and the annual national earthquake danger zone, we further judge the possible earthquake area. This study greatly reduces the range of earthquake location predicted by geomagnetic low point displacement method.

By establishing the stress-driven post-seismic afterslip model, this paper numerically simulates the post-seismic afterslip effect of 2021 M_W7.4 Maduo earthquake in Qinghai province. It then fits the GPS post-seismic deformation time-series data 160 days after the earthquake. The results show that afterslip is mainly distributed on the down-dip region and both sides of the coseismic rupture. The maximum slip is 1.24 m, and the cumulative released seismic moment is about 1.08×10¹⁹ Nm, which is equivalent to a M_W6.62 earthquake. Afterslip at the depth of 5 to 15 km accounts for about 80% of the total afterslip. The optimal fitting model shows that the reference slip rate parameters V₀ at the upper and lower regions of the fault are 6.5 m/a and 0.15 m/a, respectively, with the boundary depth of 13 km, which indicates that the difference of frictional properties at the Maduo earthquake afterslip interface is significant in the depth.

This study employs the GAMIT/GLOBK software to process data from 83 GNSS stations spanning the period from January of 2009 to June of 2019. The study obtains the velocities of the GNSS stations within the ITRF2014 framework and constructs a three-dimensional velocity field model of Guangxi using the Kriging interpolation method. By combining observations from 136 GNSS stations in Guangxi and its surrounding areas, we calculate the regional strain field using the grid distance weighting method and analyze its characteristics. The results indicate that the average horizontal velocity of the Guangxi region within the ITRF2014 framework is 34.95 mm/a with the predominant direction of N106.3°E. The vertical motion exhibits regional slow uplift and subsidence. The northern area, located north of 23.5°N, experiences compressional deformation characterized by dominant compressive strain in the SN and NW directions. In contrast, the southern region displays extensional deformation with dominant tensile strain oriented in a west-to-east fan-shaped pattern. The shear strain field demonstrates higher values in the peripheral regions and lower values in the central transitional zone. Over the past decade, earthquakes in the region primarily occur in the transition zone from high to low shear strain, showcasing spatial and temporal migration as well as back-and-forth movement along the fault zone.

In this paper, the glacier deformation is obtained by using offset-tracking technology as a supplement to SBAS-InSAR, and the pre-disaster deformation of Sedongpu basin is calculated by using two technologies from January 2018 to October 2018, and the pre-disaster deformation characteristics and influencing factors are jointly analyzed. The results show that the glaciers and gullies in Sedongpu basin were deformed before the ice avalanche occurred on October 17, 2018. The trend of the main deformation area of glacier is first accelerated, then gentle and then accelerated, with the deformation of -7.69 m from July to September. The sediments in channels showed a long-term downward trend, and the deformation rate accelerated after July. The temperature rise is the main factor for the occurrence of debris flow disaster. The combination of SBAS-InSAR and offset-tracking can meet the monitoring requirements of different deformation magnitudes, and can be used for early identification and deformation inversion of ice avalanche disasters, providing a reference for ice avalanche disaster prevention and control in the Tibetan plateau.

Based on theoretical analysis, we propose the concepts of apparent azimuth and apparent declination of ground tilt, and introduce the procedure of calculating the apparent declination. We use the observed data of five measurement components of the water pipe tiltmeter from 1987 to 2021 in Beijing Yanqing Xibozi and Gansu Lanzhou Shilidian stations as examples. In turn, we calculate the results for the apparent declination of the 715 measured component observations of the national ground tilt network in 2020. Results from two typical stations show that: the Xibozi station NS direction angle of apparent declination P_NS=－0.1°; EW direction angle of apparent declination P_EW=9.6°; NE direction angle of apparent declination P_NE=12.4°; the Shilidian station NS direction angle of apparent declination P_NS=0.3°; EW direction angle of apparent declination P_EW=－22.5°; the maximum apparent deflection angle of 2 stations is 23.2°, the minimum value is －36.0°. From the statistical mean of the 5 components, the maximum value of the apparent deviation angle is 12.4°, the minimum value is －22.5°, and the range is 34.9°. Both stations show that the number of apparent deflections in the NS direction is relatively small, while the number of apparent deflections in the EW direction and NE directions is relatively large. The calculation results of the observed data from the national earth tilt network indicate that there are 266 components with an apparent deviation angle P_S<10°, accounting for 37.20%, the number of components with an apparent deviation angle of P_S<22.5° is 445, accounting for 62.24%, and the number of components with P_S>45° is 111, accounting for 15.52%; the number of components with apparent deviation angle dispersion error M_PS<10° is 247, accounting for 34.55%, the number of M_PS<22.5° is 446, accounting for 62.38%, and the number of components with M_PS>45° is 43, accounting for 6.01%. Based on the results of this study, we recommend that the initial azimuth angle of the measurement component with an apparent deviation number greater than 20° should be emphatically checked; also we should carefully screen the observation data of the measurement component with an apparent deviation angle dispersion error M_PS>20°.

We combine improved complete empirical mode decomposition with adaptive noise (ICEEMDAN) and distributive entropy(DistEn) to propose a method to suppress the random noise of the extensometer signal without customizing the parameters and with good denoising effect. Firstly, the signal of the extensometer is processed by ICEEMDAN, and several intrinsic mode functions (IMF) are obtained.Then the distributive entropy value of each IMF component is calculated, and according to the magnitude of different distributive entropy values and the degree of chaos of the characterized component signals, each IMF is targeted to be traded off. Finally, linear reconstruction is performed. Designing simulated signal denoising experiments and SS-Y extensometer signal denoising experiments, the results show that the scaler signal reconstruction based on the ICEEMDAN-DistEn denoising model has significantly better reduction and denoising effect than several denoising models such as CEEMDAN-DistEn, wavelet denoising and Kalman filtering.