The strength or effective elastic thickness (Te) of the lithosphere controls its response to long-term loading, its evolution process and spatial configuration, and contains abundant geodynamic information, holding great scientific significance for the interpretation of mechanical properties, dynamic processes and mechanisms of the crust, lithosphere and even the mantle medium.We review the development of lithospheric strength research from the concept of equilibrium to the present, focusing on the historical dimension, combing the evolution of lithospheric strength research and the logical relationship between the development of various methods. The coupling between lithospheric strength and crust-mantle, effective elastic thickness of lithosphere and thickness of seismogenic layer, and anisotropy of effective elastic thickness of lithosphere are preliminarily discussed.

We propose a combinational adaptive noise reduction method combining empirical wavelet transform (EWT) and non-local mean (NLM) filtering with sample entropy (SE) optimization . This method uses SE to determine the low-frequency effective signal limit of all empirical modal components, superimposes the remaining medium and high-frequency components, and performs NLM filtering. Finally, the filtered signal and the effective signal are reconstructed as the final noise reduction signal to filter high-frequency noise. Using simulated data and measured data for experimental research, the results show that the optimized EWT-NLM method is overall better than the EMD and EWT methods. The RMSE decreases by 13.41%/10.63%(measured data/simulated data), 7.13%/5.78%, and the signal-to-noise ratio increases by 22.03%/22.54%, 9.72%/7.42%.

Aiming at the errors caused by random drift of micro-electro-mechanical system(MEMS) gyroscope, we propose a complete ensemble empirical mode decomposition with adaptive noise(CEEMDAN) denoising model with Hurst exponent. Firstly, we decompose the original signal of gyroscope by CEEMDAN to obtain a series of intrinsic mode function (IMF) with high to low frequencies and a residual margin. Secondly, we introduce the Hurst exponential modal screening mechanism, and IMF components are divided into noise IMF, mixed IMF and information IMF. Finally, we filter the mixed modal components by the adaptive Kalman filter and reconstruct the signals. The results show that CEEMDAN has higher decomposition accuracy than EMD and EEMD.Using AKF to deal with mixed mode, the signal-to-noise of reconstructed signals through the Hurst exponential screening mechanism increases by about 12% and 36% compared with permutation entropy and correlation coefficient method. Using Hurst exponential screening mechanism,the RMSE of reconstructed signals of AKF is about 23% lower than that of wavelet threshold filtering.

To solve the problem that the data interpolating empirical orthogonal functions(DINEOF) in GNSS coordinate time series interpolation are affected by low correlation sites and poor interpolation effect of continuous long vacancies, we propose the coefficent data interpolating empirical orthogonal functions(CDINEOF) method. Firstly, we calculate the correlation between the target site data and its surrounding site data, then filter out the site data with higher correlation to construct the observation matrix, and finally use DINEOF to interpolate the missing data in the observation matrix. Experiments are conducted to verify the feasibility of the new method by simulated and actual data, and the results are compared and analyzed with those of DINEOF method and polynomial interpolation method. The experimental results of simulated data show that the interpolation effect of CDINEOF method is better than that of DINEOF method and polynomial interpolation method when there are continuous long vacancies in the observed data; the experimental results of measured data show that CDINEOF method is the best in maximizing the retained variance, and the maximum variance is improved by 11.8% and 6.7% based on DINEOF method and polynomial interpolation method, respectively.

This paper assesses performance of BDS/GNSS on positioning and velocity measurement in normal waterway and reservoir waterway by precise point positioning and time-differenced carrier phase, respectively. The results show that, in normal waterway, the positioning accuracy of BDS-2 is 0.1-0.2 m. GPS, BDS-3 and BDS achieve positioning accuracy better than 0.07 m and 0.09 m on the horizontal and vertical direction, respectively. Their velocity accuracy reaches the mm/s level. Compared with signal system, positioning and velocity accuracy are improved by 30% for BDS/GPS, GPS/GLONASS/BDS/Galileo. In reservoir waterway, the accuracy of GPS is severely weakened, resulting in a 0.6 m positioning accuracy on horizontal direction. The positioning accuracy of BDS-3 and BDS is slightly reduced. After combination of multiple systems, environmental influence on positioning and velocity accuracy is substantially reduced to basically the same as the normal waterway.

In this paper, we check the quality of the HY-2B onboard GPS data, and analyze the influence of the pseudo-random pulse prior value on the reduced-dynamic precision orbit determination. At all time interval, when the prior standard deviation is 1×10^-8 m/s², the orbit determination accuracy is the highest, and the optimal pseudo-random pulse interval is 6 minutes. This study estimates the antenna phase center variations(PCV) and analyzes the influence of different resolution PCV(10°×10°, 5°×5°) models on the orbit determination results through phase residual, overlapping orbit comparison and SLR. The experimental results show that more than 4 GPS satellites can be observed in over 99% of the epochs, data integrity rate reaches 99.65%, and average RMS of multipath errors of the L1 and L2 bands are 15.7 cm and 9.5 cm respectively, proving the good performance of the domestic HY2 receiver. The orbit accuracy of internal validation reaches the centimeter level. The SLR verification RMS value is 27.8 mm without PCV model. After adding the 10°×10°, 5°×5° PCV models, the SLR verification RMS values improve 0.9 mm and 1.2 mm, respectively. The orbit accuracy of external validation also reaches the centimeter level.

We propose a multi-satellite linear regression inversion model of soil moisture with GPS/BDS dual-system combination. Taking the measured data from GNSS receivers as an example, we compare and analyze the effect of different GPS and BDS satellite combinations for inversion soil moisture. The experiments show that: 1) The combination of GPS and BDS dual-system can increase the number of effective satellites in the short observation time compared to the single-system. The multiple linear regression principle can achieve the effective fusion for dual-system satellites, which can improve the accuracy of soil moisture inversion. 2) When the combined number of GPS and BDS satellites reaches 6 or more, the inversion effect tends to be stable, and the correlation coefficients of their inversion results and soil moisture are all greater than 0.90, and the RMSE is improved by at least 25.8% compared with that of single satellite.

Firstly, we evaluate the accuracy of the meteorological parameters estimated by the GPT3 model using the data of 49 radiosonde stations adjacent to GNSS stations in China from 2017 to 2018. Secondly, combining the meteorological parameters estimated by the GPT3 model and 49 GNSS stations, we calculate the daily mean PWV, and evaluate the accuracy by radiosonde stations adjacent to GNSS stations. Finally, the results are obtained through the experiment: 1) In China, the accuracy and stability of the GPT3 model with 1° resolution are better than those with 5° resolution. The air pressure, temperature and T_m annual bias are 0.73 hPa, 1.34 K and -1.67 K, and the annual RMSE are 4.21 hPa, 3.75 K and 4.15 K. 2) The accuracy of PWV based on temperature inversion by GPT3 model combined with Bevis empirical formula is similar to that by GPT3 model Tm, and the PWV obtained by the two methods and PWV obtained by the sounding data show good consistency; furthermore, the accuracy of PWV in Tibet Plateau and northwest China is better than that in the southern and northern regions.

Using the data of 18 IGS stations in Asian region and 16 radiosonde stations in China region from 2016 to 2018, the accuracy of zenith tropospheric delay (ZTD) and precipitable water vapor (PWV) inversed by GPT3 model are studied, and compared with other GPT series models. The results show that the ZTD of the GPT3-1 model has the smallest mean and maximum deviation bias values of 1.34 mm and 14.06 mm, respectively; the accuracy of GPT3 model is slightly better than GPT2w model and better than GPT2 model. The bias and root mean square error(RMSE) of the GPT3 model-derived PWV at the radiosonde stations show strong seasonal characteristics, and the GPT3-1 model has higher accuracy and stability than the GPT3-5 model, as shown by the monthly mean values of the GPT3 model-derived PWV.

This paper uses the a priori information to constrain the parameters, establishes a nonlinear inequality constrained adjustment model, and proposes a new ridge estimation algorithm for solving this adjustment model. The computational results of the two ill-posed examples in this paper show that the new ridge estimation algorithm is feasible, and the accuracy of the calculation results is higher than that of ordinary ridge estimation.

This paper processes three issues of annual variation data of lithospheric magnetic field from 2016 to 2019 in central North China. Then we grid the annual change data of ΔY element in each period，and use the node value to calculate and assign a value to the ΔY gradient space. We analyze the gradient spatial distribution of ΔY. The results show that there is a certain correspondence between high value areas and active faults. High value areas are mostly extended along one or more active faults or distributed around active faults. By using the polynomial regression method to decompose the magnetic field of lithosphere in certain scales to obtain regional background anomalies and local anomalies, the results show that there is a good correspondence between the distribution of local anomalies and active faults. There are great differences in the morphology of gradient high value areas and local anomalies in each period, but there are also some high value areas or anomaly significant areas with continuity, especially near the faults, which may be more closely related to tectonic stress.

Using GRACE satellite data, we inverse the changes of groundwater storage in North China plain from 2003 to 2015. The effectiveness of this method is verified by the groundwater level data of monitoring wells. The changes of GRACE interannual groundwater storage is decomposed based on EOF method, and we analyze the factors affecting the interannual changes of groundwater storage in North China plain combined with the annual average WFblue of winter wheat  and TRMM precipitation data. The results show that the variance contribution of the first two eigenvectors is 93.09%. The contribution rate of the first mode variance is 80.04%, and the correlation coefficient between the first mode variance and the annual average WFblue spatial change of winter wheat in North China plain from 2003 to 2009 is -0.69, with consistent spatial distribution; the contribution rate of the second mode variance is 13.05%, and the correlation coefficient with the spatial distribution of precipitation data in the same period is 0.93. This research shows that the agricultural irrigation, especially for winter wheat, plays a vital role in the depletion of groundwater in the North China plain.

We analyze the temporal and spatial terrestrial water storage(TWS) changes in the Loess plateau from April 2002 to December 2016 using the COST-G GRACE temporal gravity field model, and data including precipitation, temperature, surface water(SW) of the GLDAS model, measured shallow groundwater(GW), NDVI. Then, we use the partial least squares regression method to qualitatively analyze the driving factors of TWS changes in the Loess plateau. The results show that: 1) During the study period, the TWS changes of the Loess plateau have the characteristics of rising-declining-declining gently, and the loss of TWS in Shanxi province is obvious. 2) From 2004 to 2009, the coal mining water, human domestic water, and vegetation effect are important factors for the loss of TWS in the Loess plateau. Industrial water, human domestic water and temperature rise are important factors for the decline of TWS in the Loess plateau from 2010 to 2016.

We use the cusp catastrophe model to evaluate the stability of landslide. Then we construct the combined landslide prediction model based on ensemble empirical mode decomposition, GM (1,1) model and support vector machine. The analysis of Biandianzhan landslide shows that the catastrophe characteristic values of each monitoring point are greater than 0, that is, they are in a stable state. The average relative error of the prediction results is small, which verifies the applicability of the prediction model. Through extrapolation prediction, the landslide deformation will be further increased and the stability will get worse.

We propose a 3D deformation fusion method based on Helmert variance component estimation(HVCE) and radial basis function neural network(RBFNN), and fuse the data of GNSS and InSAR monitoring to obtain the 3D surface deformation field of Jinchuan West Second mining area in Jinchang, Gansu. The results show that the accuracy of 3D deformation fields obtained by HVCE-RBFNN method are higher than that obtained by traditional methods, and the RMSE of east-west direction, north-south direction and vertical direction is 20.85 mm, 7.41 mm and 34.47 mm, respectively. The maximum deformation values in three directions are 228 mm, 300 mm and 193 mm, respectively. The spatial distribution of goaf deformation conforms to the law of mining subsidence.

Based on the stratified medium model of crust and upper mantle, this study calculates the coseismic and postseismic Coulomb stress changes generated by historical M>6 earthquakes since 1822 and the interseismic stress accumulation in six fault segments near the east Anatolian fault zone by combining coseismic deformation, viscoelastic relaxation and tectonic loading effects. The results show that the overall coseismic stress change is insignificant in triggering the 2020 Elaz?? M_W6.8 earthquake because of stress unloading from the 1875 M6.7 earthquake, even though 14 events contribute to the occurrence of the Elaz?? M_W6.8  earthquake. Postseismic and interseismic Coulomb stress changes play important roles in triggering the Elaz?? M_W6.8  earthquake. The high Coulomb stress accumulations in the Turkoglu, Lake Hazar, and Yedisu segments indicate the future seismic hazard on these zone needs more attention.

We employ Sentinel-1A SAR data to extract the coseismic deformation field and 2.5D deformation field of the 2021 Shuanghu, Tibet M_W5.7 earthquake for further inversion to obtain the fault slip distribution model. The seismogenic structure is determined by calculating the difference of Coulomb stress changes caused by different nodal solutions for receiving faults, and combining the aftershocks distribution to evaluate the future seismic risk. The results show that the epicenter is 34.37°N, 87.71°E, the focal depth is 6.51 km, and the seismogenic fault tends to the east, strike is 33°, dip is 50°, and average slip angle is -74°. There is a small amount of sinistral strike-slip component; the maximum slip is 0.26 m. In a short period, the seismic risk in the southern part of the earthquake area is relatively small, but the seismic risk in the northern part needs to be further analyzed with more data. The 2021 Shuanghu earthquake is a dispersive deformation on the Huangshuihu normal fault, resulting from the continuous EW-direction extension of the Qiangtang block, and the SN-direction graben in Huangshuihu is further expanded.

By calculating the acceleration PSD values and the corresponding PDF values of the continuous surface and borehole observations at Erenhot seismic station, the interference characteristics of sandstorms on the environmental noise level of the seismic station and the effect of downhole observations on suppressing sandstorms are studied. The results show that the sandstorms interfere with the ambient noise level of the seismic stations, mainly in the frequency bands of 4 Hz, 9 Hz, 10-20 Hz and below 10 s. The sand and dust mainly affect the background noise in the frequency band of 10-20 Hz, the high wind mainly affects the background noise near 4 Hz and 9 Hz, and the three-divisional background noise below 10 s has a certain correlation with the wind direction. 10 s-4 Hz band sandstorms have no effect on the environmental noise level. The borehole observation can better suppress the interference of sandstorms on the ambient noise level of the seismic stations.

We introduce a two-dimensional tiltmeter based on a cylindrical pendulum body and an arc cylindrical plate; we theoretically analyze the arc cylindrical plate differential capacitor. The analysis shows that to improve the sensitivity of the tiltmeter, it is necessary to appropriately increase the radius, the height of the cylindrical pendulum body and the length of the hanger wire, and to reduce the central angle of the arc cylindrical plate and the distance between the moving plate and the fixed plate; to reduce the non-linearity of the tiltmeter, it is necessary to appropriately  increase the radius of the cylindrical pendulum body and the distance between the moving plate and the fixed plate, and reduce the central angle of the arc cylindrical plate, the height of the cylindrical pendulum body, the length of the hanger wire. Based on the above principles, we select a set of typical parameters, and the theoretical calculation shows that the sensitivity of the tiltmeter is 0.028 5 V/(″), and the non-linearity is 0.001 2%.