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.

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.

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 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.

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.

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.

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.

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.

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.

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.

We take typhoon Irma as an example, conduct a study on spaceborne GNSS-R typhoon position inversion based on CYGNSS satellite. The experimental results show that CYGNSS-related observations can effectively detect the occurrence of typhoon events. By utilizing CYGNSS measurements and DBSCAN clustering algorithm, the typhoon center position can be effectively retrieved, with a minimum deviation of about 30 km and an average deviation of about 45 km. This study helps to further expand the application scope of spaceborne GNSS-R in typhoon monitoring.

When designing a robust total least-squares(RTLS) estimation algorithm based on M-estimation theory, the total least-squares(TLS) estimation is not suitable for residual prediction, and reweighting based on individual random variable residuals has theoretical flaws. We derive the TLS estimation iteration formula based on multiplicative error model, theoretically explain the equation residuals or total residuals, and explain that this residual has the properties of least-squares(LS) estimation residuals. Then, considering the robustness in both observation space and structural space, an RTLS estimation algorithm is designed based on equation residuals or total residuals. Finally, through Monte Carlo experiments, the RTLS algorithm is compared with other reweighting strategies in terms of robustness, efficiency, and iteration speed, demonstrating the advantages of the proposed RTLS algorithm.

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.

Aiming at the problems of single data structure and low resolution of ocean tide model in"specifications for the first and second order leveling", four recent high-resolution global ocean tide models are corrected using the high precision China offshore model, and the influence of four offshore correction ocean tide models on precise leveling and the effect of ocean tide loading correction are calculated and analyzed. The results show that the DTU10 offshore correction model is the most practical and accurate ocean tide loading correction model for precise leveling in China's coastal area, and the influence of ocean tide loading on leveling height difference above 400 km from the coast is negligible (the correction of ocean tide loading per kilometer is not more than 0.005 mm).

The gravity recovery and climate experiment(GRACE) mission and followed missions can provide unconstrained monthly time-varying gravity fields that are polluted by north-south striping noise. This noise is defined as a quasi-periodic oscillation along longitude, propagating continuously along latitude. Aiming at this characteristic, we introduce the moving average smoothing technique to suppress the noise in spatial domain, implementing different degrees of smoothing based on the different prior knowledge between ocean and land. Then, the proposed method is compared with common DDK filters in spatial, frequency, and time domains, showing a comparable filtering effect. The evaluation results show that the noise level of proposed method in ocean is about 20 mm, which is lower than that of DDK5-DDK7(26.20-50.25 mm). Although there are limitations such as the setting of sliding window size depends on experience, the proposed method does not need to know the variance information between signal and noise in advance and can provide a new idea for the design of novel filters.

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.

In response to the problem that traditional seismometer insulation cover cannot meet the instrument working environment indicators at low temperature and cannot maintain a constant temperature in working environment, an intelligent seismometer insulation cover has been developed using graphene material and popular 3D printing technology, taking into account the observation environment requirements of seismometer. According to indoor and outdoor testing and analysis, the intelligent insulation cover can meet the monitoring environment requirements of seismometer, with a temperature fluctuation of less than 1 ℃, a universal power supply demand of 12 V, intelligent constant temperature, lightweight instrument, simple operation, and wide applicability. It can be used in poorly conditioned observation chamber and low temperature outdoor environment.