The vertical deformation field of the epicentral region before and after the 2013 Minxian-Zhangxian M_S6.6 earthquake is obtained by using the leveling data of Lanzhou-Tianshui-Wudu regional leveling from 1973 to 2014. The results show that: (1) From 1999~2006 regional vertical deformation field, the earthquake is located at the transition zone from the uplift zone of NNW-NWW to the subsidence zone near EW,  and is also a reflection of the tectonic activity difference zone between the Minshan and Qinling mountains. (2) From the evolutionary process of the Longxi-Minxian leveling section along the NNE direction near the west of the epicenter, the vertical deformation has obvious characteristics of stage deformation, and it finally shows the mutation before the earthquake. Among them: in 1973~1993, there is a pressure uplift area with the maximum rise of nearly 40 mm between Zhangxian and Minxian. The uplift area disappears and turns flat. the overall profile of the section fluctuates, and the range is about 10 mm from 1993~2008. There is no obvious vertical difference movement on both sides of the west Qinling fault and Lintan-Tanchang fault. A subsidence gradient zone near 40 km appears on both sides of the Lintan-Tanchang fault between Zhangxian and Minxian relative to the Longxi basin in 2008~2011. Among them, three leveling points, Wuding 80, Wuding 78 and Wuding 77, which are within 16 km of the epicenter, have a downward mutation synchronously, close to or more than twice the normal range of changes since 1973. Relative to Longxi basin, the recovery between Zhangxian and Minxian is mainly thrusting and uplifting. In 2011~2014, the deformation zone on both sides of the Lintan-Tanchang fault before the earthquake did not exist, and the above 3 leveling points are also restored to the interval before the earthquake. (3) On the basis of summing up the deformation precursors before Minxian-Zhangxian M_S6.6 earthquake, in view of the current controversy about the characteristics of deformation acceleration or mutation before the earthquake, we infer that if the spatio-temporal scale of the deformation data is sufficient, at least the moderate strong earthquakes in some tectonic regions can be caught before the earthquake.

We calculate the Coulomb failure stress change caused by the 2008 Wenchuan earthquake by choosing model parameters, such as the 2008 Wenchuan earthquake rupture models, the fault parameters of 2017 Jiuzhaigou earthquake, and the effective friction coefficient. Our results show that the sum of co-seismic and post-seismic Coulomb stress change until 2017 is about 3~7 kPa at the epicenter of the Jiuzhaigou earthquake, which is less than the triggering threshold (10 kPa). The 2008 Wenchuan earthquake might have promoted the 2017 Jiuzhaigou earthquake to some degree. However, the triggering is not the main cause of the occurrence of the 2017 Jiuzhaigou earthquake. By analyzing the stress results from the models with various model parameters, we find that the rupture model of 2008 Wenchuan earthquake has the greatest impact on the results. Using a different rupture model of the 2008 Wenchuan earthquake might be the main reason for the different results from previous studies.

Based on fracture distribution model, which uses a mixed inversion of geodetic data, this study calculates the rupture process of the Beichuan fault from the perspective of the Coulomb stress calculation. The results of this paper offer evidence on stress of the rupture of the Beichuan fault from southwest to northeast. The Beichuan fault is divided into five faults in this paper, and the Coulomb stress changes on the subsequent fault are calculated respectively. The results show that: 1) The Coulomb stress produced by Yingxiu-Hongkou section in most areas of Longmenshan-Qingping section is positive. The same is true for other segments, such as Longmenshan-Qingping section in Gaochuan-Beichuan section, Gaochuan-Beichuan section in Beichuan-Pingdong section and Beichuan-Pingdong section in the Nanba-Qingchuan section. 2) The rupture of the 81.7% area in the Gaochuan-Beichuan section was triggered by the rupture of the Longmenshan-Qingping section. However, the previous continuous fault(Yingxiu-Hongkou section) had little effect on the rupture of Gaochuan-Beichuan section. 3) the rupture of the 83.2% area of Beichuan-Pingdong section was triggered mainly by the rupture of the Gaochuan-Beichuan section. The previous continuous fault(Yingxiu-Hongkou section and Longmenshan-Qingping section) had little effect on the rupture of Beichuan-Pingdong section. 4) The rupture of 99.4% of the area in the Nanba-Qingchuan section was mainly triggered by the rupture of Beichuan-Pingdong section. The previous continuous fault(Yingxiu-Hongkou section, Longmenshan-Qingping section and Gaochuan-Beichuan section) had little effect on the rupture of Beichuan-Pingdong section. This paper also calculates the stress triggering effect of Beichuan fault on Pengguan fracture. We speculate that the rupture of Yingxiu-Hongkou section triggered the rupture of most areas of Pengguan fault, and the rupture of Longmenshan-Qingping section triggered the rupture of a small part of the Pengguan fault.

Based on the digital waveforms of the eastern China seismic network, the best double-couple focal mechanism and the depth of the Wuwei M_L4.1 earthquake of April 6, 2008 is determined using the CAP method, and the earthquake sequence from 2016 in Wuwei area is relocated using the HypoDD method. The result shows that the best double couple solution of the M_L4.1 event is strike 120°, dip 57°, rake 27° and strike 15°, dip 68°, rake 144°, respectively. The depth of the centroid of the Wuwei M_L4.1 event is about 12 km. The relocation of the Wuwei earthquake sequence shows it to be distributed along the southwestern boundary of Wuwei basin in the southeast direction, with the earthquake sequence propagated from northwest to southeast. According to the focal mechanism derived using the CAP method and the relocation of earthquake sequence from 2016 in the Wuwei area, we estimate the fault plane solution for Wuwei M_L4.1 earthquake is the nodal plane I. Possible, Wuwei M_L4.1 earthquake is generated by the movement of the northwesterly fault, which is at the base of the southwestern boundary of the Wuwei basin under regional stress field.

In order to investigate the occurrences, properties and shallow tectonic features of the east-Qingshui river fault, we complete high resolution shallow seismic profiles crossing the fault and obtain shallow seismic reflection stacked profiles which have higher signal-noise ratio. According to these results, and combined with geological data, we analyze and discuss the shallow structures features of the fault. The results show that east-Qingshui river fault is a near SN trending and E dipping reverse fault. In the shallow position the east-Qingshui river, the fault shows “Y” structure which consists of 2-3 fault. The fault disrupts 10~20 m Quaternary strata in the shallow part, therefore it buried active faults in the Quaternary period.

Using waveform data from Yunnan regional digital station network, we analyze the spatio-temporary variations of wave velocity ratio before and after M_S≥ 5.5 earthquakes in western Yunnan and southwest Yunnan since 2011. Using the Wadati method of single station and multi-earthquake, we undertake dynamic tracking analysis on the variation characteristics of wave velocity versus time course curves of various stations within 160 km before the earthquakes, The results show that before the five earthquakes, there were low value anomalies, high value anomalies, low value-high value-low  value anomalies, high value-normal medium-term anomalies, accounting for 56%, 33%, 16% and 15% respectively, and low value-high value returns, high value persistence, and low value persistence three short-term and imminent anomalies, accounting for 41%, 31% and 28% respectively. Comparative analysis of wave velocity ratio anomalies in different directions in the earthquake area show that before the two Yingjiang earthquakes, the obvious anomaly area is located in the southeast of the earthquake source, the prominent anomaly area before the Eryuan earthquake is located in the northeast of the earthquake source, and the obvious anomaly area before the Jinggu earthquake is located in Lincang area in the northwest of the Lancang river fault.

We correct the gravity change obtained by the vertical change rate to the gravity change of CG-5 by CORS, plot the real regional gravity field map of the Maoshan fault zone, and analyze the gravity field changes in this area. 18 relative gravity points near the Maoshan fault zone are selected for synchronous GPS-RTK measurement. We compare and analyze the measured data, and calculate the height variation of the GPS as the basis of the gravity value. On the basis of the gravity value of 2014, we correct the gravity measured values of three periods from 2016 to 2017 by the gradient variation, and draw the anomalous contour map of the gravity field to study the anomalous variation of the gravity field in the Maoshan fault zone. The results show that the contrast of the gravitational field difference diagram before the elevation correction shows that the shape of the gravity field changes greatly, and the direction of the high gradient area and the zero line are all changed. The research results are of great significance for determining the annual anomaly area based on the trend of differential variation.

We discover a new minimum curvature algorithm, based on the idea that the constraints are treated as unknown sites. The improved method avoids complicated reduction, without the need to consider the relationship between constraint points and unknown points when the constraint points exist around the unknown points. Furthermore, precision is improved.

For the two-layered homogeneous medium model, this paper gives the error formula caused by Hilbert transform in the Bostick inversion process,explains the numerical calculation method of error,and gives the modification formula by means of theoretical derivation.The inversion calculation of the two models shows that the modified Bostick inversion method can better reflect the first layer depth and the resistivity of the basement.

Based on analysis of combined precise point positioning (PPP) model, we investigate single- and dual-frequency real-time static and kinematic GPS and GPS/Galileo precise point positioning, using multi-GNSS real-time orbit and clock products released by Centre National d’Etudes Spatiales (CNES). Through the ten days observations from ten Multi-GNSS experiment (MGEX) stations, the solutions of different PPP models are then obtained. The results show that GPS/Galileo combined PPP outperforms GPS-only. However, while the accuracy of GPS/Galileo combined PPP is slightly better than GPS-only PPP for single- and dual-frequency real-time static modes, it presents a significant improvement for real-time kinematic mode. Compared with GPS-only PPP, the average accuracies of GPS/Galileo combined PPP are notably improved by 5.4%, 4.9% and 10.4%, which are 10.6 cm, 9.8 cm and 22.5 cm in the east, north and up directions, respectively, in the single-frequency kinematic positioning. Furthermore, the accuracies of dual-frequency real-time kinematic GPS/Galileo are about 4.3 cm, 2.9 cm and 7.0 cm in the E, N and U directions, respectively; these results present increases by 6.5%, 6.5% and 5.4% compared with GPS-only PPP. Moreover, the GPS/Galileo combination PPP has a certain improvement over the convergence time of a single GPS system.

With the modernization of GPS, there are currently 7 Block ⅡR-M satellites and 12 Block ⅡF satellites capable of broadcasting L2C signals, achieving initial operational capability. We process the high-rate data of 27 stations in the IGS network during DOY 1-7 of the year 2016 using precise point positioning (PPP). The improvement of L2C-based over L2P-based ionosphere-free combinations is directly examined in position domain. The experimental results show that the P1/L2C combination observations exhibit 7.4%, 7.4% and 4.4% accuracy improvements in the east, north and up components, respectively, compared to the traditional P1/L2P combination PPP dynamic positioning results. In addition, L2C signals can be stably tracked and do not easily lose lock, which is appreciated for preserving the continuity of satellite observation and for solving ambiguities in PPP data processing.

In order to enhance the signal-to-noise ratio (SNR) of signal extraction, the singular spectrum analysis (SSA) method is used to decompose and reconstruct the geodesic height time series, using the simulation experiment to determine the principle of selecting the embedding dimension and the number of truncated principal components. Furthermore, the SSA method is applied to the extraction of deformation information of CORS. By FFT analysis, we find that the geodetic height time series mainly consists of decomposed seasonal variation components, and the standard deviation of time series after reconstruction is significantly reduced. Our research shows that the SSA method can effectively improve the geodetic height time series SNR of CORS and play a role in noise reduction and smoothing. The research results have certain significance for the expression of vertical deformation of the crust and the expansion of SSA applications.

This paper uses time series InSAR to obtain ground deformation results from 2013 to 2015 in the Wuhan urban area with 27 TerraSAR-X images. The InSAR results show that the ground subsidence mainly lies in Houhu area, Gongye road and Optics Valley square. The maximum subsidence rate is up to 78.1 mm/a. Analysis of geological data and field investigation show that the subsidence is mainly caused by the hydraulic head drop and loading increasing due to large-scale urban construction on the soft soils foundation. Additionally, a strong correlation is highlighted between the deformation in the bank of Yangtze river and the water level records of the Yangtze river, implying that this previously unknown deformation phenomenon is likely related to seasonal influence of water levels in the Yangtze river on the confined groundwater in the bank areas.

In this paper, we use the synthetic aperture radar time series analysis method to analyze the deformation of Yangjuzhuang, a residential area in the Huainan mining area. We use 13 consecutive Sentinel satellite radar images from December 2016 to May 2017 (one cycle of 12 d). According to the deformation characteristics of the mining area, we propose a combined prediction model of grey support vector machine (GM-SVR) to predict the deformation of the mining area. The results of this model are compared with the results of the traditional single gray model and the support vector machine prediction model. The results show that the combination of InSAR time series analysis technology and the GM-SVR model can realize the rapid deformation monitoring and disaster prevention of the mining area, and provide a new method for the monitoring and early warning of mining disasters.

According to the relationship between geoid and deflection of the vertical,a simplified formula for calculating deflection of the vertical using geoid model is given by designing a reasonable calculation scheme.The influence of the relative accuracy of geoid model,the distance between two points,the selection of known points and the number of known points on the calculation results,are discussed by simulating calculation.Using the GEOID12B model,the deflection of the vertical of the stations in the GSVS2011 and GSVS2014 projects and the western region of the United States (40°~45°N,100°~105°W,resolution is 1') are calculated respectively. The calculated results are compared with the measured values of the GSVS projects and the DEFLEC12B model values.The results show that the calculation accuracy of the north-south component and the east-west component of the deflection of the vertical is better than ±0.5″. It is shown that the geoid models with relative accuracy of cm level or even sub cm level can obtain higher accuracy deflection of the vertical.

When the spherical target is used as the feature point of the same name for point cloud data registration, if there is a large amount of noise in the vicinity of the target with interference or scanning target point cloud, it will have a great influence on the point cloud registration quality. In view of the current situation that the point cloud registration has neglected target self-scanning noise, the characteristics of spherical target are analyzed, the applicability of the wavelet threshold denoising method is discussed, and the method of selecting the wavelet base function is tested. A wavelet threshold denoising method of the spherical target point cloud discrete noise is proposed. Experimental results show that the denoising of the target's own point cloud cannot be neglected; the result of case analysis shows that the method can filter the rough noise near the sphere more effectively, the fitting accuracy of the center position of a single spherical target is increased by about 0.8 mm, as compared with the point cloud stitching result of the spherical target without denoising. The co-ordinate stitching distance error of the scan feature check point is reduced by about 5 mm, and the registration accuracy of the point cloud is increased by about 20%. It is an efficient preprocessing method for point cloud registration data, and can provide reference for the application of related engineering.

The general ill-posed problem is that there are several singular eigenvalues in the coefficient matrix, and the singular value can be corrected with the target matrix in the calculation process. In the total least squares iteration process, the coefficient matrix is constantly changing, so the target matrix should also change accordingly. For target matrix changing, this paper deduces two new methods of ill-posed total least-squares targeting singular value corrections. By finding the new coefficient matrix and then finding the target matrix, the iteration is calculated with the parameter estimate and used in the example. The results show that these methods have some advantages.

In this paper,based on the least square adjustment criterion, the ill-posed adjustment problem is transformed into an unconstrained quadratic programming problem. At the same time, the influence of ill-posed problems on the solution of the adjustment is analyzed by using optimization theory. The conjugate gradient search algorithm is used to find the optimal step size factor in the feasible region and automatically ascertain the steepest descent direction. The setting method of iterative initial value is given, and we analyze the relationship between ill-posed problems and local optimal solutions in approximate calculation, which gives a fast-iterative method of local optimal solution. We also analyze the validity of the algorithm and the speed of iteration through two examples. The algorithm can be used to deal with the highly ill-posed adjustment problem of large-scale coefficient matrices becausethe inverse matrix about the coefficient matrix of normal equation is not calculated in the whole calculation process.

Using the observation data of the vertical pendulum tiltmeter in China, we study the influence of different sampling rates on the results of power spectral density. We emphatically analyze the background noise level of the seismic frequency band (200~600 s) of different stations and different types of instruments. The conclusions are as follows: (1) Both single station and national statistics show that the noise levels of the two types of pendulum tiltmeter are equal in the seismic frequency band. (2) There is no obvious regularity in the regional distribution, but due to the influence of ocean and active tectonic movement, the noise levels of some stations in coastal areas are relatively high. (3) The curves of high noise level instrument are generally not smooth and burr-prone. Except for some stations affected by the ocean, they are mostly caused by the observation environment or the instrument itself.

The HHT method based on clustering empirical mode decomposition(EEMD) is used to extract the time-frequency characteristics of the strong earthquake record of Kangding M_S6.3 earthquake. The EEMD and Hilbert transform and spectrum analysis are performed on the strong vibration acceleration records acquired by each station. We compare with the Fourier transform. The results show that for nonlinear strong earthquake recording, EEMD can effectively suppress the modal aliasing problem existing in EMD. The results of the earthquake damage investigation in Kangding earthquake area show that the seismic damage characteristics of the collapsed building houses are more serious. It can be seen from the Hilbert marginal spectrum analysis that the main frequency of the stations in the earthquake zone is concentrated at around 10 Hz, and the instantaneous energy spectrum is high. The information is richer, and the poor seismic resistance of Tibetan buildings is also an important reason for the earthquake-damaged Tibetan-style structural houses.