We obtain the density variation in the crust from the Jiuzhaigou MS 7.0 earthquake in 2017, deriving it from the dynamic variation of gravity in 2014~2017, using the compact gravity inversion method: (1) before the Jiuzhaigou MS7.0 earthquake, variation of gravity in the large space range appears in the survey area, while forming a high gradient zone of gravity change along the Zhangye-Xining-Jiuzhaigou; (2) the density variation in the crust increases with depth, and is up to 0.2 g/cm3 at 45 km depth around; (3) during the early period before the MS7.0 Jiuzhaigou earthquake (2014-04~2017-04), regional density variation is distributed in a four-quadrant form. The materials migration is dominated by left-lateral strike motion, which is same as the focal mechanism solutions. The results show the tectonic movement related to the occurrence of this earthquake before the Jiuzhaigou earthquake, and that strong earthquakes occur easily in places where material migration is concentrated.

Using 3848 P-wave arrival times of 593 earthquakes in the northern Greater Khingan range area from observation data of Inner Mongolia seismic network from January 1, 2009 to March 30, 2017, 1-D crustal P-wave velocity model, relocation and station correction value are inversed. The results of different initial models converge reasonably well, and through the speed disturbance test, the inversion result is relatively stable. The results obtained by joint inversion show the lateral heterogeneity of the crustal velocity and the wave velocity abnormality below the stations. The velocity of the southeast side of the northern segment of Greater Khingan range is higher than that of the northwest side. In the relocation results obtained by joint inversion, the location of the epicenter is more convergent in space. The focal depth profile shows that focal depth of the northwest side is shallow, yet deep in the southeast. In the Greater Khingan range ridge area, the focal depth distribution has a deeper lower limit.

The present-day crustal deformation rates near 91° E in the middle section of the Altyn Tagh fault zone are obtained using SBAS InSAR based on 14 ALOS PALSAR scene imagery from 2007 to 2010, and the slip velocities and the locked depth in different segments are calculated as well. The results show that the deformation pattern from north to south is characterized by linear decrease with three different rate gradients. The rates are 8~12 mm/a in the eastern part of the Altyn mountains, 6~7 mm/a in the Xorkol basin, and 0 mm/a in the south of the Altyn Tagh fault, respectively. The significant rate changes of the three sections are concentrated on the two fractured zones of the Kaladaban fault and the Altyn Tagh fault. The best fitted fault is located at the southern margin of Jinyan mountains. The strike-slip rates increase from 7.1 mm/a in the west to 14.0 mm/a in the east. The locking depth is increased from 4.5 km in the west to 10.6 km in the east. Referring to previous research results, it is inferred that the Jinyan mountain and the Xorkol basin form a composite fault structure, which is the main adjustment model of strain and stress during the transition fault movements.

Using seismic and geodetic methods, we analyze the seismicity of the northern segment of the Yishu fault zone after the 2011 M9.0 magnitude earthquake in Japan. It is considered that the relative quiescence of seismicity in the region since 2012 is due to the fact that the M9.0 earthquake in Japan affected the regional stress field. The northern section of the Yishu fault zone is greatly affected within 1 year of the earthquake, and the seismicity declined after 2 years. A time scan of b values also shows that the northern segment of the Yishu fault zone is now under low stress field control. No earthquakes greater than magnitude 4 occurred in the northern section of the Yishu fracture zone since 2012, although there is a possibility of an earthquake of magnitude 4.

Using the latest method developed by Snoke for calculating focal mechanism solutions using the combination of P wave, SV wave and SH wave (FOCMEC), we inversed the focal mechanism solutions of 176 ML≥1.0 earthquakes of two times after Jiujiang-Ruichang MS5.7 earthquake. The results show that the seismogenic fault of the mainshock MS5.7 is a sinistral strike slip fault with thrust property under the extrusion of the near EW direction stress field, with most aftershocks presenting a strike slip motion. The NW Yangjishan-Wushan-Tongjiangling buried fault forms the seismogenic structure of the main shock. The predominant strike direction of nodal planes are NEE and NWW, which is largely consistent with the predominant direction of aftershock distributions and tectonic strikes. The dominant direction of the P axis of focal mechanism solutions is nearly EW, close to the direction of P axis the main shock. It is also consistent with the distribution of tectonic stress field in northern Jiangxi. The inversion results of the whole stress field are consistent with the statistical results of the focal mechanism parameters, which show the effect of the near EW direction extrusion and the near NS tension.

Systematic analysis models were developed and set up according to actual phenomena, including inter-seismic and co-seismic dislocation deformation of fault, single fault and parallel fault system action in inter-plate, fault activity, and seismic risk analysis, etc. Actual examples show that fault action parameters and their changes in the area or along faults can be obtained by the models using crustal deformation data, including various kinds of information on co-seismic displacement and de-locking depth of Longmenshan fault zone, harmonizing action between Longmenshan and Longriba fault zone after the Wenchuan MS8.0 earthquake, spatial distribution of deformation gradient in Zhangjiakou-Bohai tectonic zone and its adjacent region, locking degree distribution along the tectonic zone, etc. Not only is the availability of the models proven, but research on the tectonic action of the fault system and its surrounding area can be enriched by the models.

In this paper, the interaction of faults is studied based on the calculation of Coulomb failure stress. From the two aspects of source fault and receiver fault, five kinds of seismic fault models are selected to study the distribution characteristics of Coulomb failure stress when these five fault models are used as source faults and receiver faults, and we analyze the influence of the different slip mechanisms of the source fault and the receiver fault on the distribution of the Coulomb failure stress. On the basis of the analysis, it is found that the fault and slip mechanism of the fault are closely related. The strike-slip fault also has a certain relationship with the left and right rotation. In addition to the skew fault, the interaction between the other faults shows a certain symmetrical relationship.

The stability and deformation trend judgment model of landslides is built based on cusp catastrophe theory and detrended fluctuation analysis. First of all, we evaluate the cusp catastrophe theory overall on the stability of landslides, and further discuss the phase stability characteristics of landslides.Secondly, the analysis of the previous stage is compared with the non-trend wave analysis to determine the cumulative sequence and velocity sequence of landslides. The overall and phased deformation trends are then compared with the stability analysis results to mutually support the accuracy of the analysis results. The example test shows that the results of the two analysis methods have good consistency, and that overall and each stage of the landslide are in stable states, albeit witha weakening trend. In the phased research process, the analysis results of the incremental period show obvious differences, indicating that the stage decomposition method has a greater impact on analysis results, and the regularity of the results of the analysis with increasing intervals is relatively stronger.

The development of structural fractures changes the mechanical properties of the reservoir rock, directly affecting the efficiency of dense reservoir exploration and development. Therefore, the development characteristics of the fractures is of very important theoretical significance and practical value. We analyze the characteristics of the fracture from geological outcrop and the underground in the Jiyuan-Yuancheng area of the Ordos basin, and combine the tectonic stress field background getting the following results in this paper: (1) the structural fracture is given priority oblique to the maximum principal stress of a single fracture, with the trend of SWW-NEE or nearly E-W and NNE-SSW or nearly S-N, and a small amount of the corresponding conjugate fracture NW-SE and NE-SW fracture develops; (2) according to the cutting relationship between the fracture system in the outcrop area, the trends of NE-SW and nearly S-N latter develop, and SWW-NEE or nearly E-W fracture develop early; (3) in the background of pressure stress field in the north west and south east of Yanshan period, the principal stress difference caused by the early cretaceous tectonic uplift is the main reason for the formation of early conjugate fractures. The stress extrusion of north east-south west in the Himalaya period is the main reason for the fracture.

The fine crustal structure and deep-shallow tectonic features in Shanxi reservoir area are explored using deep seismic reflection. The results show that the crust in this area has obvious zoning features in the vertical direction and block structures by faults in the horizontal direction. In the studied area, there is a Shuangxi-Jiaoxiyang fault, which strikes to the northwest and extends about 20 km to the mid-lower crust. It is the main controlling fault in this area, affecting the developing of lower faults in nearby regions, and is the main seismogenic structure of earthquakes in this area.

Based on measurement, obtained through the soil gas detection method, of the radon and hydrogen in soil gas on 3 different positions of Shuangxi-Jiaoxiyang fault in Shanxi reservoir district, we find that the values of radon and hydrogen in soil are higher near the fault fracture zones or veins, and the values of radon and hydrogen in soil far away from the fault fracture zones are lower. By the application of fault gas detection method in detecting buried faults, the fault crossing location near Baoshanyang village can be confirmed. We also find that the values of radon and hydrogen in soil gas crossing the seismogenic fault are significantly higher than the values crossing the non-causative fault. This shows that the radon and hydrogen in soil gas are closely related to seismicity, so continuous measurements of soil gas near the Shuangxi-Jiaoxiyang fault are suggested to provide the basis for seismic forecast and shock tendency estimation in Shanxi reservoir district.

Aiming at the problem that C/A code acquisition of GPS software receivers has a high signal-to-noise ratio threshold and slow acquisition speed, a GPS weak signal acquisition method based on average grouping and superposition correlation is proposed. First, autocorrelation loss is reduced and weak signal acquisition is improved based on the average correlation processing technique. Second, the superposition correlation is used to improve the operational efficiency of the coherent operation, and linear interpolation is used to improve the performance of the autocorrelation function. Finally, C/A signal acquisition accuracy is improved by frequency offset correction and interpolation. Theoretical analysis and simulation experiments both verify that the proposed acquisition method can achieve GPS signal acquisition at a lower signal-to-noise ratio with higher accuracy and lower computational load.

TRAIM availability models and algorithms are discussed, and the simulation platform is constructed based on STK and MATLAB software. The simulation of the four different LEOs (500 km, 650 km, 800 km and 1 400 km), based on observations of GPS and BDS, shows that the combined method can achieve the TRAIM availability probability of 99.1% when the threshold of the TRAIM is 100 ns, indicating that TRAIM availability based on BDS and GPS can meet the demand of time synchronization integrity for LEOs.

The modeling of the GPS satellite clock is studied to improve and simplify the service mode of GPS satellite clock error, reduce the communication burden, and save storage space. This paper proposes to model and analyze satellite clock error by polynomial model and mixed function model with periodic part. The result shows the periodic part plays an important role in improving the accuracy of modeled satellite clock error: for rubidium clock, the clock error of Block ⅡF can reach an accuracy of 0.03 m (about 0.1 ns), and the clock error of Block ⅡR and ⅡR-M can reach an accuracy of 0.05 m (about 0.2 ns); However, the accuracy of cesium clock is lower by an order of magnitude. Analyzed by precise point positioning, the result shows the accuracy of the positioning results of the mixed function modeled clock error can reach the centimeter level with a 4 h convergence time. The above results show that, within certain areas of application, simple modeling parameters can take the place of the complicated clock error sequence, simplifying the service mode of GPS satellite clock error.

Carrier multipath error is the main source of error for the short-range mm-level real-time relative positioning of GNSS. Sidereal filtering based on satellite orbit repetition is an effective method of multipath mitigation. The large revisiting orbital period differences among multi-class GNSS satellites lead to the limitation of multipath mitigation based on the coordinate domain sidereal filtering. In order to solve this problem, the revisiting orbital period characteristics of different types of satellites are firstly investigated and the formula for all types of satellites are also deduced. Then the multipath mitigation algorithm based on the observation domain is discussed in details. Finally, the feasibility of this algorithm is verified by the measured real dataset. Our results show that, by the sidereal filtering based on the observation domain multipath mitigation model, GPS, BDS and GPS+BDS positioning precision is improved on average by about 42%, 38%, and 54% in the north, east, and upward components, respectively.

In traditional robust estimation, the selecting weight iteration method can not detect the systematic errors, while the semiparametric model based on the least square principle can separate the systematic errors well. This paper establishs the semiparametric regression model based the selecting weight iteration method, using the time series method and L-curve methods to determine the regularization matrix and smoothing factor, and uses the selecting weight iteration method to reshape the weight matrix so as to reduce the influence of gross errors and systematic errors in parameter estimation. Using a simulated example, and taking the measured data of Daping landslide in Fengjie county of Chongqing as an additional example, the validity and superiority of the selecting weight iteration for semiparametric regression method applied to landslide prediction in the Three Gorges reservoir area is verified.

 Marine magnetic survey data needs to be converted to different heights to construct the 3D marine magnetic space background field model. The analytical continuation of the magnetic field is a key technique for this transformation. The high frequency information in survey data is easily amplified by the continuation operator, with the result that downward continuation contains lots of noise, reducing the accuracy of the 3D marine magnetic space background field model. For this problem, the 2D adaptive wavelet threshold denoising method is introduced in this paper. The noise variance is estimated in survey data by this method, setting the adaptive threshold according to different wavelet decomposition levels, and high frequency noise in the magnetic data is removed before downward continuation. Actual data processing shows that under the conditions of different noise, the denoising effect of wavelet adaptive threshold method is superior to FFT smoothing, and the result of downward continuation has a significant improvement, providing the basis for the construction of 3D marine magnetic space background field model.

This paper proposes a similar L-shaped curve method processing uncertainty selection problem of ULS, and then experiments on the dislocation model and calculating dislocation parameters. Finally, comparison of the result of ULS with those of LS and TLS, shows that ULS has higher precision, increased by nearly 60% over LS and TLS.

Aiming at the low computational efficiency of the existing vector-parameter method for multivariable observations modeling and adjustment, we propose a matrix-parameter weighted least-squares method for multivariable observations, using the equivalent transformation, Kronecker product techniques and weighted least-squares method. Considering cross-correlation of different dimensional observations, the proposed method reconstructs the vector-parameter as a matrix-parameter form that has parameter independence and isomorphism in the multivariable observations model. This reduces the dimension number of the normal matrix and increases matrix density of the coefficient matrix. Consequently, high computational efficiency can be achieved with the proposed method. The adjustment results of space linear model and IGS coordinate time series model show that both the new matrix-parameter method and the traditional vector-parameter method have the same estimation results, but the proposed method achieves higher computational efficiency.

Analysis of the data from Balguntay station’s 4-component borehole strain shows significant short-term abnormal changes in pressure. We exclude interference from equipment, weather and the environment. We consider that the abnormal change is true and may be an earthquake precursor anomaly. The anomaly is extracted using the overrun rate and S-transform time-frequency analysis. The results show the signal is concentrated in the 1 440~10 min band. The maximum signal strength of NS and EW components are 185×10-10, 140×10-10. This article also discusses the characteristics of such anomalous changes and makes a preliminary analysis of the causes.

The object of this paper is the borehole tilt and the component strain aided observation pressure data of the Balguntay; Influence of pressure on the borehole tilt is studied by correlation and wavelet analysis. The result shows: (1) The influence of pressure on the Balguntay of the borehole tilt is a quasi linear relationship; (2) The influence of the pressure on the Balguntay of the borehole tilt on the NS direction is larger than that of the EW direction; (3) The significant frequency band of pressure to NS is 2 048~8 192, 32 768~65 536 min; (4) the significant frequency band of pressure to EW is 2 048~8 192 min. The mechanism of the effect of the air pressure on the borehole tilt of Balguntay is also discussed.

We study temperature characteristic of Burris relative gravimeters, employing three gravimeters which have cooled for different times. After cooling about one month in a basement where temperature is about 14 ℃, one Burris gravimeter did not reach a constant temperature point, when the tips of bad temperature disappear, until the meter was heated 125 minutes. The zero drift rates were larger than 0.005×10-5 m·s-2/h after 65 hours and smaller than 0.003×10-5 m·s-2/h after 110 hours from the beginning of heating. After the three gravimeters cooled 15 minutes, 2 hours and 24 hours, the gravimeters show that the temperature reading sharply falls and then slightly increases and falls before the reading is stable, and the absolute change rate also decreases and then increases and decreases again. The measurement indicates that the reading is not stable until the gravimeter is heated after one hour when the gravimeter is powered off 15 minutes. In the process of heating-up, the reading sharply changes after the gravimeter reads a constant point and the minimum of reading change appears after the temperature of the meter is stable. The study indicates that the measurement precision of one of three gravimeters decreases compared with its past.