Based on the stochastic finite fault simulation method, 9 triggered strong motion earthquake stations within 100 km near field of the 2022 Luding earthquake in Sichuan were selected to simulate the strong motion. According to the principle of minimum residual between the measured and simulated, the reasonable input parameters for the simulation of the strong motion are determined, and the spatial distribution characteristics of the peak acceleration of the earthquake are obtained. The results show that, except for JLT station, the peak acceleration and response spectrum simulation results fit well with the actual observation in the period of 0.05 to 1 s. The amplitude and the spectral shape are similar, and the ground motion can be predicted well. The Luding seismic intensity map based on the simulation results is consistent with the published instrument intensity map, and the long axis of the isoseismic line shows a NW-SE direction.

To explore the influence of BDS-3 single- and dual-frequency SPP TGD correction on positioning, we select the observation data of 10 MGEX stations for 30 days to carry out SPP experiments. The results show that the BDS-3 DCB product is stable within one month without noticeable jumps, and the monthly stability is better than 0.2 ns. The TGD parameters are more consistent with the DCB products, and most satellite differences are better than 2 ns. After TGD correction, the accuracy of single-frequency and dual-frequency SPP is greatly improved in both horizontal and vertical components. The improvement rate of single-frequency SPP is 17% to 70%, and dual-frequency SPP is 66% to 90%. The hardware delay deviation has a great influence on single point positioning and cannot be ignored in the positioning solution.

To take full advantage of BDS-3 and Galileo multi-frequency signals on positioning, we make a  proper selection of BDS-3 and Galileo four-frequency wide-lane combinations, and construct multi-frequency positioning models which are suitable for BDS-3 single-system, Galileo single-system, BDS-3/Galileo dual-system as well as BDS-3/Galileo/GPS triple-system, based on the proper combinations. We compare and analyze the multi-frequency long baseline data, positioning accuracy and stability of four positioning models. The results show that when the long-baseline is over 500 km, the positioning accuracy of the BDS-3 single-system is better than that of the Galileo single-system. The positioning accuracy of the BDS-3/Galileo dual-system can reach the decimeter level in both the horizontal and vertical directions, which is more than 10% and 25% higher than that of the BDS-3 single-system, and the stability is also significantly improved. Compared with the dual-system, the positioning accuracy of the BDS-3/Galileo/GPS triple-system is improved by about 10%. The relative positioning accuracy of the dual-system and the triple-system reaches 1×10^-9 m, which can meet long-baseline precise positioning requirements. The increase of satellite systems not only increases the number of visible satellites, but also enhances the geometry of the satellites, which improves the positioning accuracy and stability effectively.

This study focuses on the long-time performance of determined and broadcast ephemeris orbit of BDS-3 satellites using the iGMAS and MGEX B1C/B2a data in the two years since the opening of the global service. The results show that the radial accuracy of Beidou-3 MEO satellite precision orbit based on the new B1C/B2a observation is about 3 cm, and the IGSO satellites is around 8 cm. Except for GEOs, the average RMS of the broadcast ephemeris orbit of Beidou-3 IGSO/MEO satellites in radial, normal and tangential directions is about 0.10 m, 0.37 m and 0.36 m, which are better than GPS satellites. The user ranging error(SISRE) caused by the satellite orbit is approximately 14 cm. However, the satellite laser ranging(SLR) residuals of the broadcast ephemeris shows that there is an obvious systematic bias in the radial direction of broadcast orbit, which might reach nearly 10 cm.

Detecting possible offsets is a key step in GPS coordinate time series preprocessing, and automatic detection of offsets is necessary for the management of dense or large GPS networks. Using real coordinate time series, we propose a new idea of automatic offset detection based on SSA, and verify the effectiveness of the method. The results show that the SSA-based method can successfully detect the offsets with obvious steps; transient motion such as postseismic deformation does not affect the detection results; however, in the case where the difference between the offsets and background motion is not obvious, this method is subject to certain limitations.

Using multi-source satellite altimetry data, we construct the mean sea surface height model with a resolution of 1′×1′ in the range of 9°-19°N and 110°-116°E, and elaborate on the methods of collinear analysis of ERM data, removal of the temporal oceanic variability of geodetic mission(GM) data, adjustment of intersections between single and multiple satellites, and gridding. The experimental results show that the mean, RMS, and STD of the difference between the mean sea surface height model and CLS15 are 0.59 cm, 2.85 cm, and 2.79 cm, respectively, and the mean, RMS, and STD of the difference with DTU18 are 2.06 cm, 4.17 cm, and 3.62 cm, respectively. We use the model-independent altimetry data(Sentinel-3B, HY-2B) to verify the accuracy of the model, use HY-2A, Jason-3 and Sentinel-3A satellite data to establish the MSS, and then compare the new data with T/P(TOPEX/Poseidon) data to analyze the effect of the new data on the MSS.

To solve the problems that most ionospheric products are based on the grid form and the low accuracy of traditional forecast models, we use a weighting function method to calculate single-station TEC and propose a sliding window-based improved MEA-BP(MW-MEA-BP) forecast model. We select the IGS stations at different latitudes to analyze and validate the observations in low and high solar activity years, respectively. The results show that the proposed single-station TEC estimation method is fast and reliable, and the MEA-BP model is a significant improvement over the BP model in short-term forecasting. When the TEC changes drastically, the forecast accuracy of the MW-MEA-BP model improves 71.8%-90.6% compared with the BP model, and 13.9%-54.4% compared with the MEA-BP model. The research can provide a priori accurate ionospheric information for positioning users.

Based on the zenith tropospheric delay(ZTD) calculated from the data of 23 continuously operating reference stations(CORS) in Anhui province, we analyze the applicability of two tropospheric model schemes, GPT3+Hopfield and GPT3+Sasstamoinen tamoinen. Using sounding data, we analyzed the accuracy of GPT3 model in estimating weighted average temperature (T_m) and the inversion accuracy of the precipitable water vapor (PWV). The results show that: 1) the ZTD accuracy of GPT3 combined with Saastamoinen model is better than that of Hopfield model. At the same time, the ZTD accuracy of GPT3 model has significant spatial-temporal distribution characteristics. The accuracy of southern Anhui is lower than that of northern Anhui, and the accuracy in spring and winter is better than in summer and autumn; 2) In Anhui province, the T_m accuracy of the two grid resolutions of GPT3 model are basically the same; the average deviation is about -2.0 K, and the RMS value is about 4.5 K; 3) In Anhui province, the PWV (GPT3-PWV) inversed based on the meteorological parameters of the GPT3 model has high consistency with the PWV of the sounding station, and also has characteristic spatial-temporal variations. It gradually decreases from the south to the north of Anhui, with the maximum in summer and the minimum in winter.

Using a construction area in Tianjin as the research object, we carry out research on InSAR surface deformation monitoring. We use PS-InSAR technology and SBAS-InSAR technology to process 54 sentinel-1b data and 65 sentinel-1a data from 2017 to 2021. We analyze the time series changes of the surface in the area due to the construction of buildings and the impact on the surrounding buildings. The results show that compared with precision leveling, the settlement of the study area is mainly concentrated around buildings under construction on both sides of the study area, and the lifting area is mainly in the building reconstruction area in the middle of the study area. During summer rainfall, the surface of the region will rise to varying degrees.

To solve the problem of unreliable monitoring accuracy of GNSS signals under the influence of environmental occlusion and multipath errors, the idea of variance expansion is introduced into the GNSS/accelerometer fusion filtering algorithm based on Huber’s weight selection iteration method, which adaptively adjusts the measurement noise of GNSS anomalies from the perspective of stochastic model, reduces the influence of GNSS anomaly observation on Kalman filtering measurement update, and improves the reliability of GNSS/accelerometer fusion deformation monitoring results. The results show that the improved fusion algorithm can significantly improve the accuracy of GNSS monitoring in a complex multi-path environment, and the RMS of deformation displacement obtained by its solution is within 1.8 cm in 3D direction, which can provide a reference for high-precision deformation monitoring in complex environments.

We take a landslide near Libi coal mine in Qinshui county, Shanxi province as an example to carry out high-precision deformation monitoring for almost one year. By constructing strain models under small deformation conditions and finite deformation conditions, we study the spatial and temporal characteristics of the deformation field of the target landslide at different stages before, during and after sliding. Through analysis of the maximum and minimum principal strain fields, we find that the retaining wall of Libi coal mine before anchor cable reinforcement still has about 40% inhibitory effect on the accelerated sliding of the early landslide front. The compressive impact between the landslide front and the retaining wall has obvious spatiotemporal inhomogeneity, that is, the direction and strength of principal compressive strain between them have obvious spatiotemporal variations. The local strong strain anomaly of the landslide may be a significant indicator of the structural failure of the monitoring target. The local strong tensile deformation at 830 m contour in the study area on December 13, 2020, has good correspondence with a transverse 10-20 cm wide cracking on the slope. Under the steady-state background where the overall migration and relative deformation of the landslide are small, the occurrence and development of cracks on the slope surface indicate that the failure and development of the landslide are still continuous. In the post-sliding adjustment stage, the deformation mode of the whole landslide, especially the trailing edge where sliding occurs, is quite complex, and it also experiences compression deformation and tension deformation with similar strength. The landslide, after 3 months, was not completely stable, and only a local sliding trend like the direction of the original main sliding axis was initially formed in the middle part of the trailing edge.

Based on the near-field InSAR deformation of Sentinel-1 and ALOS-2, this paper uses the finite fault method to invert the source rupture slip distribution of the January 8, 2022, Menyuan M_W6.6 earthquake. The results show that the maximum slip of the earthquake is about 3.65 m, and the released seismic moment is about 1.56×10¹⁹ Nm. The rupture propagates to the surface and is divided into east and west sections,. The rupture slip extends from the epicenter to the SEE and NWW along the fault, and the fault slip is larger on the southeast side of the epicenter. Different from other studies, we propose that ruptures mainly occur in the shallow part of the eastern section, no more than 8 km, and the rupture on the western section can be as deep as 15 km. The coseismic deformation is generally consistent with the characteristics of left-lateral strike-slip rupture, showing the relative motion characteristics of the blocks in the Tibetan plateau.

We use the dual-track D-InSAR technique to obtain the synoptic deformation fields of the May 21, 2021 earthquake in Yangbi county, Yunnan province, on ascending and descending tracks, and use them as constraints to invert the geometric parameters and synoptic sliding distribution of the seismic fault based on the Okada uniform elastic half-space dislocation model. The results show that the maximum deformation in the InSAR deformation field is about 10 cm in the ascending LOS direction and about 13 cm in the descending LOS direction; the Okada model inversion shows that the seismic fault is about 12.53 km long and 6.44 km wide, located at 3-9 km underground, with a strike angel of about 136.34°, a dip angel of about 83.79°, and a slip angle of about -175.46°. The maximum slip displacement is 0.64 m at a depth of 4 km below ground. The earthquake occurred on an unknown NW-SE fault zone, which may be a secondary or branch fault of the Weixi-Qiaohou-Weishan and north Honghe fault zones.

To solve the problem of uncertainty in the estimation of vertical ground motion parameters, we propose a prediction model based on random adaptive neuro fuzzy inference. Firstly, based on PEER NGA strong motion database from Pacific Earthquake Engineering Research Center, we take as input parameters the earthquake magnitude, fault distance and average shear wave velocity, and take the PGA and PGV as estimation targets to establish training data sets and test data sets. Secondly, according to the prediction equation of ground motion parameters, we use random adaptive neuro fuzzy inference technology to construct the prediction model of vertical ground motion parameters to predict PGA and PGV, and give comprehensive parameter study and reliability test. The vertical ground motion attenuation of ANFIS model shows the near-field strong earthquake saturation effect, site amplification effect and soft soil damping effect of PGA. The average absolute percentage error of ANFIS model is about 0.15. Compared with Campbell-Bozorgnia ground motion attenuation relationship, the accuracy of PGA and PGV prediction is improved by about 77.4% and 62.7% respectively, thus has better estimation accuracy.

Based on travel time data of the first arrival P and S waves for earthquakes with M_L≥1.5 from 2017 to 2022, using the Wadati method of signal earthquake and multi-station, we calculate and discuss the variations of the wave velocity ratio near the epicenter of the September 16, 2021 M_S6.0 earthquake in Luxian, Sichuan Province. The results show that before the Luxian M_S6.0 earthquake, the wave velocity ratio near the epicenter decreased in 1 year and 3 months, then rose again from the low value to the mean value in half a year. The low value area of the wave velocity ratio was concentrated around the epicenter. In 2019, before the Weiyuan M_S5.4 earthquake and Zizhong M_S5.2 earthquake about 66 km northwest of the Luxian M_S6.0 earthquake, the seismic wave velocity ratio around it also showed a similar decline to recovery change, with a decline time of about 2 years. The two earthquakes occurred in the process of recovery, and the wave velocity ratio continued to rise after the earthquakes until the Luxian earthquake occurred. The epicenters of the two earthquakes were also in the concentration area of the low value of the wave velocity ratio.

At same time and point on the earth, crustal deformation and vibration are identical, but the recording of different observation instruments differs. One important metric affecting earthquake forecast is that the precursory signal in one kind of record cannot be found in another at the same site. We calculate the amplitude-spectrum of the data from extension-meter and water-tube tiltmeter and analyze the relation between amplitude-spectrum and capability for anomaly signal detecting. The results show that when an anomaly signal is weak, it may appear only in one recording but not in others at the same site. So, if an anomaly signal in one recording cannot be found in others at the same site, it cannot be evidence for falsification. This argument is supported by field data in Yunlong and Yongsheng stations.

We propose an integrated signal conditioning method to adapt the pendulum tiltmeter to the needs of stability and light weight. The method uses FPGA and ARM circuits to implement modulation and demodulation of signals, filtering, and noise reduction. The experimental results show that the signal circuit has strong anti-interference capability, high integration and is worth of continuing theoretical and applied research.

We systematically summarize the borehole design, electrode placement method, observation method, technical measures, and test indicators of the Tongwei underground resistivity observation system. Using the morphological and the mean square error methods, we compare and analyze the data of the original surface observation system and the new underground observation system and discuss the seismic reflection capability of the downhole observation system. The results show that the downhole observation system can suppress surface electromagnetic interference, significantly improve the signal-to-noise ratio and the dispersion of the data compared with the ground observation system; It also has some ability to reflect the surrounding earthquakes. It can eliminate the influence of changes in shallow surface resistance caused by meteorological factors, improve data stability, and alleviate the contradiction between geoelectric observation land and social economy and urban development. It is an optimal choice to adapt to the development of seismic electromagnetic disciplines under the new situation.